op-supervisor: use event system like op-node, for easy synchronization (#13752)

* op-supervisor: use event system like op-node, for easy synchronization

* op-supervisor,op-node: simplify local-safe derivation updates

* op-supervisor: fixes, report back problem if local-safe update fails

* op-e2e: fix fp interop action test

* op-service: bigger timeout on eventual-case in poll test

op-e2e/actions/helpers/l2_verifier.go

@@ -41,10 +41,6 @@ var interopJWTSecret = [32]byte{4}
 
 type InteropControl interface {
 	PullEvents(ctx context.Context) (pulledAny bool, err error)
-
-	AwaitSentCrossUnsafeUpdate(ctx context.Context, minNum uint64) error
-	AwaitSentCrossSafeUpdate(ctx context.Context, minNum uint64) error
-	AwaitSentFinalizedUpdate(ctx context.Context, minNum uint64) error
 }
 
 // L2Verifier is an actor that functions like a rollup node,
@@ -448,21 +444,6 @@ func (s *L2Verifier) ActL2InsertUnsafePayload(payload *eth.ExecutionPayloadEnvel
 	}
 }
 
-func (s *L2Verifier) AwaitSentCrossUnsafeUpdate(t Testing, minNum uint64) {
-	require.NotNil(t, s.InteropControl, "must be managed by op-supervisor")
-	require.NoError(t, s.InteropControl.AwaitSentCrossUnsafeUpdate(t.Ctx(), minNum))
-}
-
-func (s *L2Verifier) AwaitSentCrossSafeUpdate(t Testing, minNum uint64) {
-	require.NotNil(t, s.InteropControl, "must be managed by op-supervisor")
-	require.NoError(t, s.InteropControl.AwaitSentCrossSafeUpdate(t.Ctx(), minNum))
-}
-
-func (s *L2Verifier) AwaitSentFinalizedUpdate(t Testing, minNum uint64) {
-	require.NotNil(t, s.InteropControl, "must be managed by op-supervisor")
-	require.NoError(t, s.InteropControl.AwaitSentFinalizedUpdate(t.Ctx(), minNum))
-}
-
 func (s *L2Verifier) SyncSupervisor(t Testing) {
 	require.NotNil(t, s.InteropControl, "must be managed by op-supervisor")
 	_, err := s.InteropControl.PullEvents(t.Ctx())

op-e2e/actions/interop/interop.go

@@ -17,7 +17,7 @@ import (
 	"github.com/ethereum-optimism/optimism/op-e2e/actions/helpers"
 	"github.com/ethereum-optimism/optimism/op-e2e/e2eutils"
 	"github.com/ethereum-optimism/optimism/op-node/rollup"
-	"github.com/ethereum-optimism/optimism/op-service/eth"
+	"github.com/ethereum-optimism/optimism/op-node/rollup/event"
 	"github.com/ethereum-optimism/optimism/op-service/sources"
 	"github.com/ethereum-optimism/optimism/op-service/testlog"
 	"github.com/ethereum-optimism/optimism/op-supervisor/config"
@@ -128,32 +128,22 @@ func (is *InteropSetup) CreateActors() *InteropActors {
 
 // SupervisorActor represents a supervisor, instrumented to run synchronously for action-test purposes.
 type SupervisorActor struct {
+	exec    *event.GlobalSyncExec
 	backend *backend.SupervisorBackend
 	frontend.QueryFrontend
 	frontend.AdminFrontend
 }
 
-func (sa *SupervisorActor) SyncEvents(t helpers.Testing, chainID types.ChainID) {
-	require.NoError(t, sa.backend.SyncEvents(chainID))
+func (sa *SupervisorActor) ProcessFull(t helpers.Testing) {
+	require.NoError(t, sa.exec.Drain(), "process all supervisor events")
 }
 
-func (sa *SupervisorActor) SyncCrossUnsafe(t helpers.Testing, chainID types.ChainID) {
-	err := sa.backend.SyncCrossUnsafe(chainID)
-	if err != nil {
-		require.ErrorIs(t, err, types.ErrFuture)
-	}
-}
-
-func (sa *SupervisorActor) SyncCrossSafe(t helpers.Testing, chainID types.ChainID) {
-	err := sa.backend.SyncCrossSafe(chainID)
-	if err != nil {
-		require.ErrorIs(t, err, types.ErrFuture)
-	}
+func (sa *SupervisorActor) SignalLatestL1(t helpers.Testing) {
+	require.NoError(t, sa.backend.PullLatestL1())
 }
 
-func (sa *SupervisorActor) SyncFinalizedL1(t helpers.Testing, ref eth.BlockRef) {
-	sa.backend.SyncFinalizedL1(ref)
-	require.Equal(t, ref, sa.backend.FinalizedL1())
+func (sa *SupervisorActor) SignalFinalizedL1(t helpers.Testing) {
+	require.NoError(t, sa.backend.PullFinalizedL1())
 }
 
 // worldToDepSet converts a set of chain configs into a dependency-set for the supervisor.
@@ -182,10 +172,12 @@ func NewSupervisor(t helpers.Testing, logger log.Logger, depSet depset.Dependenc
 		Datadir:               supervisorDataDir,
 		SyncSources:           &syncnode.CLISyncNodes{}, // sources are added dynamically afterwards
 	}
-	b, err := backend.NewSupervisorBackend(t.Ctx(),
-		logger.New("role", "supervisor"), metrics.NoopMetrics, svCfg)
+	evExec := event.NewGlobalSynchronous(t.Ctx())
+	b, err := backend.NewSupervisorBackend(t.Ctx(), logger, metrics.NoopMetrics, svCfg, evExec)
 	require.NoError(t, err)
+	b.SetConfDepthL1(0)
 	return &SupervisorActor{
+		exec:    evExec,
 		backend: b,
 		QueryFrontend: frontend.QueryFrontend{
 			Supervisor: b,

op-e2e/actions/interop/interop_test.go

@@ -37,15 +37,8 @@ func TestFullInterop(gt *testing.T) {
 	status := actors.ChainA.Sequencer.SyncStatus()
 	require.Equal(t, uint64(0), status.UnsafeL2.Number)
 
-	// sync chain A
-	actors.Supervisor.SyncEvents(t, actors.ChainA.ChainID)
-	actors.Supervisor.SyncCrossUnsafe(t, actors.ChainA.ChainID)
-	actors.Supervisor.SyncCrossSafe(t, actors.ChainA.ChainID)
-
-	// sync chain B
-	actors.Supervisor.SyncEvents(t, actors.ChainB.ChainID)
-	actors.Supervisor.SyncCrossUnsafe(t, actors.ChainB.ChainID)
-	actors.Supervisor.SyncCrossSafe(t, actors.ChainB.ChainID)
+	// sync initial chain A and B
+	actors.Supervisor.ProcessFull(t)
 
 	// Build L2 block on chain A
 	actors.ChainA.Sequencer.ActL2StartBlock(t)
@@ -62,9 +55,7 @@ func TestFullInterop(gt *testing.T) {
 	actors.ChainA.Sequencer.SyncSupervisor(t)
 
 	// Verify as cross-unsafe with supervisor
-	actors.Supervisor.SyncEvents(t, actors.ChainA.ChainID)
-	actors.Supervisor.SyncCrossUnsafe(t, actors.ChainA.ChainID)
-	actors.ChainA.Sequencer.AwaitSentCrossUnsafeUpdate(t, 1)
+	actors.Supervisor.ProcessFull(t)
 	actors.ChainA.Sequencer.ActL2PipelineFull(t)
 	status = actors.ChainA.Sequencer.SyncStatus()
 	require.Equal(t, head, status.UnsafeL2.ID())
@@ -83,6 +74,7 @@ func TestFullInterop(gt *testing.T) {
 	// it needs the supervisor to see the L1 block first,
 	// and provide it to the node.
 	actors.ChainA.Sequencer.ActL2EventsUntil(t, event.Is[derive.ExhaustedL1Event], 100, false)
+	actors.Supervisor.SignalLatestL1(t)          // supervisor will be aware of latest L1
 	actors.ChainA.Sequencer.SyncSupervisor(t)    // supervisor to react to exhaust-L1
 	actors.ChainA.Sequencer.ActL2PipelineFull(t) // node to complete syncing to L1 head.
 
@@ -97,12 +89,14 @@ func TestFullInterop(gt *testing.T) {
 	n := actors.ChainA.SequencerEngine.L2Chain().CurrentSafeBlock().Number.Uint64()
 	require.Equal(t, uint64(0), n)
 
+	// Make the supervisor aware of the new L1 block
+	actors.Supervisor.SignalLatestL1(t)
+
 	// Ingest the new local-safe event
 	actors.ChainA.Sequencer.SyncSupervisor(t)
 
 	// Cross-safe verify it
-	actors.Supervisor.SyncCrossSafe(t, actors.ChainA.ChainID)
-	actors.ChainA.Sequencer.AwaitSentCrossSafeUpdate(t, 1)
+	actors.Supervisor.ProcessFull(t)
 	actors.ChainA.Sequencer.ActL2PipelineFull(t)
 	status = actors.ChainA.Sequencer.SyncStatus()
 	require.Equal(t, head, status.UnsafeL2.ID())
@@ -119,8 +113,8 @@ func TestFullInterop(gt *testing.T) {
 	actors.L1Miner.ActL1FinalizeNext(t)
 	actors.ChainA.Sequencer.ActL1SafeSignal(t) // TODO old source of finality
 	actors.ChainA.Sequencer.ActL1FinalizedSignal(t)
-	actors.Supervisor.SyncFinalizedL1(t, status.HeadL1)
-	actors.ChainA.Sequencer.AwaitSentFinalizedUpdate(t, 1)
+	actors.Supervisor.SignalFinalizedL1(t)
+	actors.Supervisor.ProcessFull(t)
 	actors.ChainA.Sequencer.ActL2PipelineFull(t)
 	finalizedL2BlockID, err := actors.Supervisor.Finalized(t.Ctx(), actors.ChainA.ChainID)
 	require.NoError(t, err)
@@ -155,15 +149,8 @@ func TestInteropFaultProofs(gt *testing.T) {
 	status := actors.ChainA.Sequencer.SyncStatus()
 	require.Equal(t, uint64(0), status.UnsafeL2.Number)
 
-	// sync chain A
-	actors.Supervisor.SyncEvents(t, actors.ChainA.ChainID)
-	actors.Supervisor.SyncCrossUnsafe(t, actors.ChainA.ChainID)
-	actors.Supervisor.SyncCrossSafe(t, actors.ChainA.ChainID)
-
-	// sync chain B
-	actors.Supervisor.SyncEvents(t, actors.ChainB.ChainID)
-	actors.Supervisor.SyncCrossUnsafe(t, actors.ChainB.ChainID)
-	actors.Supervisor.SyncCrossSafe(t, actors.ChainB.ChainID)
+	// sync chain A and B
+	actors.Supervisor.ProcessFull(t)
 
 	// Build L2 block on chain A
 	actors.ChainA.Sequencer.ActL2StartBlock(t)
@@ -180,16 +167,11 @@ func TestInteropFaultProofs(gt *testing.T) {
 	actors.ChainB.Sequencer.SyncSupervisor(t)
 
 	// Verify as cross-unsafe with supervisor
-	actors.Supervisor.SyncEvents(t, actors.ChainA.ChainID)
-	actors.Supervisor.SyncEvents(t, actors.ChainB.ChainID)
-	actors.Supervisor.SyncCrossUnsafe(t, actors.ChainA.ChainID)
-	actors.Supervisor.SyncCrossUnsafe(t, actors.ChainB.ChainID)
-	actors.ChainA.Sequencer.AwaitSentCrossUnsafeUpdate(t, 1)
+	actors.Supervisor.ProcessFull(t)
 	actors.ChainA.Sequencer.ActL2PipelineFull(t)
 	status = actors.ChainA.Sequencer.SyncStatus()
 	require.Equal(gt, uint64(1), status.UnsafeL2.Number)
 	require.Equal(gt, uint64(1), status.CrossUnsafeL2.Number)
-	actors.ChainB.Sequencer.AwaitSentCrossUnsafeUpdate(t, 1)
 	actors.ChainB.Sequencer.ActL2PipelineFull(t)
 	status = actors.ChainB.Sequencer.SyncStatus()
 	require.Equal(gt, uint64(1), status.UnsafeL2.Number)
@@ -202,6 +184,7 @@ func TestInteropFaultProofs(gt *testing.T) {
 	actors.L1Miner.ActL1IncludeTx(actors.ChainA.BatcherAddr)(t)
 	actors.L1Miner.ActL1IncludeTx(actors.ChainB.BatcherAddr)(t)
 	actors.L1Miner.ActL1EndBlock(t)
+	actors.Supervisor.SignalLatestL1(t)
 	// The node will exhaust L1 data,
 	// it needs the supervisor to see the L1 block first, and provide it to the node.
 	actors.ChainA.Sequencer.ActL2EventsUntil(t, event.Is[derive.ExhaustedL1Event], 100, false)
@@ -223,13 +206,10 @@ func TestInteropFaultProofs(gt *testing.T) {
 	actors.ChainB.Sequencer.SyncSupervisor(t)
 
 	// Cross-safe verify it
-	actors.Supervisor.SyncCrossSafe(t, actors.ChainA.ChainID)
-	actors.Supervisor.SyncCrossSafe(t, actors.ChainB.ChainID)
-	actors.ChainA.Sequencer.AwaitSentCrossSafeUpdate(t, 1)
+	actors.Supervisor.ProcessFull(t)
 	actors.ChainA.Sequencer.ActL2PipelineFull(t)
 	status = actors.ChainA.Sequencer.SyncStatus()
 	require.Equal(gt, uint64(1), status.SafeL2.Number)
-	actors.ChainB.Sequencer.AwaitSentCrossSafeUpdate(t, 1)
 	actors.ChainB.Sequencer.ActL2PipelineFull(t)
 	status = actors.ChainB.Sequencer.SyncStatus()
 	require.Equal(gt, uint64(1), status.SafeL2.Number)

op-node/rollup/interop/managed/system.go

@@ -115,16 +115,19 @@ func (m *ManagedMode) OnEvent(ev event.Event) bool {
 		ref := x.Ref.BlockRef()
 		m.events.Send(&supervisortypes.ManagedEvent{UnsafeBlock: &ref})
 	case engine.LocalSafeUpdateEvent:
+		m.log.Info("Emitting local safe update because of L2 block", "derivedFrom", x.DerivedFrom, "derived", x.Ref)
 		m.events.Send(&supervisortypes.ManagedEvent{DerivationUpdate: &supervisortypes.DerivedBlockRefPair{
 			DerivedFrom: x.DerivedFrom,
 			Derived:     x.Ref.BlockRef(),
 		}})
 	case derive.DeriverL1StatusEvent:
+		m.log.Info("Emitting local safe update because of L1 traversal", "derivedFrom", x.Origin, "derived", x.LastL2)
 		m.events.Send(&supervisortypes.ManagedEvent{DerivationUpdate: &supervisortypes.DerivedBlockRefPair{
 			DerivedFrom: x.Origin,
 			Derived:     x.LastL2.BlockRef(),
 		}})
 	case derive.ExhaustedL1Event:
+		m.log.Info("Exhausted L1 data", "derivedFrom", x.L1Ref, "derived", x.LastL2)
 		m.events.Send(&supervisortypes.ManagedEvent{ExhaustL1: &supervisortypes.DerivedBlockRefPair{
 			DerivedFrom: x.L1Ref,
 			Derived:     x.LastL2.BlockRef(),

op-service/locks/rwmap.go

@@ -12,6 +12,20 @@ type RWMap[K comparable, V any] struct {
 	mu    sync.RWMutex
 }
 
+// Default creates a value at the given key, if the key is not set yet.
+func (m *RWMap[K, V]) Default(key K, fn func() V) (changed bool) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	if m.inner == nil {
+		m.inner = make(map[K]V)
+	}
+	_, ok := m.inner[key]
+	if !ok {
+		m.inner[key] = fn()
+	}
+	return !ok // if it exists, nothing changed
+}
+
 func (m *RWMap[K, V]) Has(key K) (ok bool) {
 	m.mu.RLock()
 	defer m.mu.RUnlock()

op-service/locks/rwmap_test.go

@@ -60,4 +60,27 @@ func TestRWMap(t *testing.T) {
 
 	// remove a non-existent value
 	m.Delete(132983213)
+
+	m.Set(10001, 100)
+	m.Default(10001, func() int64 {
+		t.Fatal("should not replace existing value")
+		return 0
+	})
+	m.Default(10002, func() int64 {
+		return 42
+	})
+	v, ok = m.Get(10002)
+	require.True(t, ok)
+	require.Equal(t, int64(42), v)
+}
+
+func TestRWMap_DefaultOnEmpty(t *testing.T) {
+	m := &RWMap[uint64, int64]{}
+	// this should work, even if the first call to the map.
+	m.Default(10002, func() int64 {
+		return 42
+	})
+	v, ok := m.Get(10002)
+	require.True(t, ok)
+	require.Equal(t, int64(42), v)
 }

op-service/tasks/poll.go

+package tasks
+
+import (
+	"context"
+	"sync"
+	"time"
+
+	"github.com/ethereum-optimism/optimism/op-service/clock"
+)
+
+// Poller runs a function on repeat at a set interval.
+// Warning: ticks can be missed, if the function execution is slow.
+type Poller struct {
+	fn func()
+
+	clock    clock.Clock
+	interval time.Duration
+
+	ticker clock.Ticker // nil if not running
+
+	mu     sync.Mutex
+	ctx    context.Context // non-nil when running
+	cancel context.CancelFunc
+	wg     sync.WaitGroup
+}
+
+func NewPoller(fn func(), clock clock.Clock, interval time.Duration) *Poller {
+	return &Poller{
+		fn:       fn,
+		clock:    clock,
+		interval: interval,
+	}
+}
+
+// Start starts polling in a background routine.
+// Duplicate start calls are ignored. Only one routine runs.
+func (pd *Poller) Start() {
+	pd.mu.Lock()
+	defer pd.mu.Unlock()
+	if pd.ctx != nil {
+		return // already running
+	}
+
+	pd.ctx, pd.cancel = context.WithCancel(context.Background())
+
+	pd.ticker = pd.clock.NewTicker(pd.interval)
+
+	pd.wg.Add(1)
+	go func() {
+		defer pd.wg.Done()
+
+		defer pd.ticker.Stop()
+
+		for {
+			select {
+			case <-pd.ticker.Ch():
+				pd.fn()
+			case <-pd.ctx.Done():
+				return // quiting
+			}
+		}
+	}()
+}
+
+// Stop stops the polling. Duplicate calls are ignored.
+// Only if active the polling routine is stopped.
+func (pd *Poller) Stop() {
+	pd.mu.Lock()
+	defer pd.mu.Unlock()
+	if pd.ctx == nil {
+		return // not running, nothing to stop
+	}
+	pd.cancel()
+	pd.wg.Wait()
+	pd.ctx = nil
+	pd.cancel = nil
+	pd.ticker = nil
+}
+
+// SetInterval changes the polling interval.
+func (pd *Poller) SetInterval(interval time.Duration) {
+	pd.mu.Lock()
+	defer pd.mu.Unlock()
+	pd.interval = interval
+	// if we're currently running, change the interval of the active ticker
+	if pd.ticker != nil {
+		pd.ticker.Reset(interval)
+	}
+}

op-service/tasks/poll_test.go

+package tasks
+
+import (
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/ethereum-optimism/optimism/op-service/clock"
+)
+
+const eventualTimeout = 10 * time.Second
+
+func TestPoller(t *testing.T) {
+	cl := clock.NewDeterministicClock(time.Now())
+	counter := new(atomic.Int64)
+	poller := NewPoller(func() {
+		counter.Add(1)
+	}, cl, time.Second*5)
+
+	poller.Start()
+
+	cl.AdvanceTime(time.Second * 6) // hit the first tick
+
+	require.Eventually(t, func() bool {
+		t.Log("counter", counter.Load())
+		return counter.Load() == 1
+	}, eventualTimeout, time.Millisecond*100)
+
+	cl.AdvanceTime(time.Second * 3) // no hit yet, 9 seconds have passsed now
+
+	require.Never(t, func() bool {
+		return counter.Load() == 2
+	}, time.Second, time.Millisecond*100)
+
+	// hit the second tick at 10s
+	cl.AdvanceTime(time.Second * 2) // 11 seconds have passed now
+	require.Eventually(t, func() bool {
+		return counter.Load() == 2
+	}, eventualTimeout, time.Millisecond*100)
+
+	poller.Stop()
+
+	// Poller was stopped, this shouldn't affect it
+	cl.AdvanceTime(time.Second * 1000)
+
+	// We should have stopped counting
+	require.Never(t, func() bool {
+		return counter.Load() > 2
+	}, time.Second, time.Millisecond*100)
+
+	// Start back up
+	poller.Start()
+	// No previously buffered ticks
+	require.Never(t, func() bool {
+		return counter.Load() > 2
+	}, time.Second, time.Millisecond*100)
+
+	// Change the interval, so we poll faster
+	poller.SetInterval(time.Second * 2)
+
+	cl.AdvanceTime(time.Second * 3)
+	require.Eventually(t, func() bool {
+		t.Log("counter", counter.Load())
+		return counter.Load() == 3
+	}, eventualTimeout, time.Millisecond*100)
+
+	poller.Stop()
+}

op-supervisor/supervisor/backend/backend.go

@@ -11,6 +11,7 @@ import (
 	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/ethereum/go-ethereum/log"
 
+	"github.com/ethereum-optimism/optimism/op-node/rollup/event"
 	"github.com/ethereum-optimism/optimism/op-service/client"
 	"github.com/ethereum-optimism/optimism/op-service/eth"
 	"github.com/ethereum-optimism/optimism/op-service/locks"
@@ -22,6 +23,7 @@ import (
 	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend/depset"
 	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend/l1access"
 	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend/processors"
+	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend/superevents"
 	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend/syncnode"
 	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/frontend"
 	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/types"
@@ -33,6 +35,11 @@ type SupervisorBackend struct {
 	m       Metrics
 	dataDir string
 
+	eventSys event.System
+
+	sysContext context.Context
+	sysCancel  context.CancelFunc
+
 	// depSet is the dependency set that the backend uses to know about the chains it is indexing
 	depSet depset.DependencySet
 
@@ -44,10 +51,8 @@ type SupervisorBackend struct {
 
 	// chainProcessors are notified of new unsafe blocks, and add the unsafe log events data into the events DB
 	chainProcessors locks.RWMap[types.ChainID, *processors.ChainProcessor]
-	// crossProcessors are used to index cross-chain dependency validity data once the log events are indexed
-	crossSafeProcessors   locks.RWMap[types.ChainID, *cross.Worker]
-	crossUnsafeProcessors locks.RWMap[types.ChainID, *cross.Worker]
-	syncSources           locks.RWMap[types.ChainID, syncnode.SyncSource]
+
+	syncSources locks.RWMap[types.ChainID, syncnode.SyncSource]
 
 	// syncNodesController controls the derivation or reset of the sync nodes
 	syncNodesController *syncnode.SyncNodesController
@@ -59,13 +64,17 @@ type SupervisorBackend struct {
 	// chainMetrics are used to track metrics for each chain
 	// they are reused for processors and databases of the same chain
 	chainMetrics locks.RWMap[types.ChainID, *chainMetrics]
+
+	emitter event.Emitter
 }
 
+var _ event.AttachEmitter = (*SupervisorBackend)(nil)
 var _ frontend.Backend = (*SupervisorBackend)(nil)
 
 var errAlreadyStopped = errors.New("already stopped")
 
-func NewSupervisorBackend(ctx context.Context, logger log.Logger, m Metrics, cfg *config.Config) (*SupervisorBackend, error) {
+func NewSupervisorBackend(ctx context.Context, logger log.Logger,
+	m Metrics, cfg *config.Config, eventExec event.Executor) (*SupervisorBackend, error) {
 	// attempt to prepare the data directory
 	if err := db.PrepDataDir(cfg.Datadir); err != nil {
 		return nil, err
@@ -90,14 +99,16 @@ func NewSupervisorBackend(ctx context.Context, logger log.Logger, m Metrics, cfg
 		}
 	}
 
+	eventSys := event.NewSystem(logger, eventExec)
+
+	sysCtx, sysCancel := context.WithCancel(ctx)
+
 	// create initial per-chain resources
 	chainsDBs := db.NewChainsDB(logger, depSet)
+	eventSys.Register("chainsDBs", chainsDBs, event.DefaultRegisterOpts())
 
-	l1Accessor := l1access.NewL1Accessor(
-		logger,
-		nil,
-		processors.MaybeUpdateFinalizedL1Fn(context.Background(), logger, chainsDBs),
-	)
+	l1Accessor := l1access.NewL1Accessor(sysCtx, logger, nil)
+	eventSys.Register("l1Accessor", l1Accessor, event.DefaultRegisterOpts())
 
 	// create the supervisor backend
 	super := &SupervisorBackend{
@@ -109,10 +120,15 @@ func NewSupervisorBackend(ctx context.Context, logger log.Logger, m Metrics, cfg
 		l1Accessor: l1Accessor,
 		// For testing we can avoid running the processors.
 		synchronousProcessors: cfg.SynchronousProcessors,
+		eventSys:              eventSys,
+		sysCancel:             sysCancel,
+		sysContext:            sysCtx,
 	}
+	eventSys.Register("backend", super, event.DefaultRegisterOpts())
 
 	// create node controller
-	super.syncNodesController = syncnode.NewSyncNodesController(logger, depSet, chainsDBs, super)
+	super.syncNodesController = syncnode.NewSyncNodesController(logger, depSet, eventSys, super)
+	eventSys.Register("sync-controller", super.syncNodesController, event.DefaultRegisterOpts())
 
 	// Initialize the resources of the supervisor backend.
 	// Stop the supervisor if any of the resources fails to be initialized.
@@ -124,6 +140,31 @@ func NewSupervisorBackend(ctx context.Context, logger log.Logger, m Metrics, cfg
 	return super, nil
 }
 
+func (su *SupervisorBackend) OnEvent(ev event.Event) bool {
+	switch x := ev.(type) {
+	case superevents.LocalUnsafeReceivedEvent:
+		su.emitter.Emit(superevents.ChainProcessEvent{
+			ChainID: x.ChainID,
+			Target:  x.NewLocalUnsafe.Number,
+		})
+	case superevents.LocalUnsafeUpdateEvent:
+		su.emitter.Emit(superevents.UpdateCrossUnsafeRequestEvent{
+			ChainID: x.ChainID,
+		})
+	case superevents.LocalSafeUpdateEvent:
+		su.emitter.Emit(superevents.UpdateCrossSafeRequestEvent{
+			ChainID: x.ChainID,
+		})
+	default:
+		return false
+	}
+	return true
+}
+
+func (su *SupervisorBackend) AttachEmitter(em event.Emitter) {
+	su.emitter = em
+}
+
 // initResources initializes all the resources, such as DBs and processors for chains.
 // An error may returned, without closing the thus-far initialized resources.
 // Upon error the caller should call Stop() on the supervisor backend to clean up and release resources.
@@ -137,21 +178,23 @@ func (su *SupervisorBackend) initResources(ctx context.Context, cfg *config.Conf
 		}
 	}
 
+	eventOpts := event.DefaultRegisterOpts()
 	// initialize all cross-unsafe processors
 	for _, chainID := range chains {
 		worker := cross.NewCrossUnsafeWorker(su.logger, chainID, su.chainDBs)
-		su.crossUnsafeProcessors.Set(chainID, worker)
+		su.eventSys.Register(fmt.Sprintf("cross-unsafe-%s", chainID), worker, eventOpts)
 	}
 	// initialize all cross-safe processors
 	for _, chainID := range chains {
 		worker := cross.NewCrossSafeWorker(su.logger, chainID, su.chainDBs)
-		su.crossSafeProcessors.Set(chainID, worker)
+		su.eventSys.Register(fmt.Sprintf("cross-safe-%s", chainID), worker, eventOpts)
 	}
 	// For each chain initialize a chain processor service,
 	// after cross-unsafe workers are ready to receive updates
 	for _, chainID := range chains {
 		logProcessor := processors.NewLogProcessor(chainID, su.chainDBs, su.depSet)
-		chainProcessor := processors.NewChainProcessor(su.logger, chainID, logProcessor, su.chainDBs, su.onIndexedLocalUnsafeData)
+		chainProcessor := processors.NewChainProcessor(su.sysContext, su.logger, chainID, logProcessor, su.chainDBs)
+		su.eventSys.Register(fmt.Sprintf("events-%s", chainID), chainProcessor, eventOpts)
 		su.chainProcessors.Set(chainID, chainProcessor)
 	}
 	// initialize sync sources
@@ -184,32 +227,6 @@ func (su *SupervisorBackend) initResources(ctx context.Context, cfg *config.Conf
 	return nil
 }
 
-// onIndexedLocalUnsafeData is called by the event indexing workers.
-// This signals to cross-unsafe workers that there's data to index.
-func (su *SupervisorBackend) onIndexedLocalUnsafeData() {
-	// We signal all workers, since dependencies on a chain may be unblocked
-	// by new data on other chains.
-	// Busy workers don't block processing.
-	// The signal is picked up only if the worker is running in the background.
-	su.crossUnsafeProcessors.Range(func(_ types.ChainID, w *cross.Worker) bool {
-		w.OnNewData()
-		return true
-	})
-}
-
-// onNewLocalSafeData is called by the safety-indexing.
-// This signals to cross-safe workers that there's data to index.
-func (su *SupervisorBackend) onNewLocalSafeData() {
-	// We signal all workers, since dependencies on a chain may be unblocked
-	// by new data on other chains.
-	// Busy workers don't block processing.
-	// The signal is picked up only if the worker is running in the background.
-	su.crossSafeProcessors.Range(func(_ types.ChainID, w *cross.Worker) bool {
-		w.OnNewData()
-		return true
-	})
-}
-
 // openChainDBs initializes all the DB resources of a specific chain.
 // It is a sub-task of initResources.
 func (su *SupervisorBackend) openChainDBs(chainID types.ChainID) error {
@@ -237,8 +254,6 @@ func (su *SupervisorBackend) openChainDBs(chainID types.ChainID) error {
 
 	su.chainDBs.AddCrossUnsafeTracker(chainID)
 
-	su.chainDBs.AddSubscriptions(chainID)
-
 	return nil
 }
 
@@ -308,7 +323,7 @@ func (su *SupervisorBackend) attachL1RPC(ctx context.Context, l1RPCAddr string)
 // if the L1 accessor does not exist, it is created
 // if an L1 source is already attached, it is replaced
 func (su *SupervisorBackend) AttachL1Source(source l1access.L1Source) {
-	su.l1Accessor.AttachClient(source)
+	su.l1Accessor.AttachClient(source, !su.synchronousProcessors)
 }
 
 func (su *SupervisorBackend) Start(ctx context.Context) error {
@@ -323,22 +338,6 @@ func (su *SupervisorBackend) Start(ctx context.Context) error {
 		return fmt.Errorf("failed to resume chains db: %w", err)
 	}
 
-	if !su.synchronousProcessors {
-		// Make all the chain-processors run automatic background processing
-		su.chainProcessors.Range(func(_ types.ChainID, processor *processors.ChainProcessor) bool {
-			processor.StartBackground()
-			return true
-		})
-		su.crossUnsafeProcessors.Range(func(_ types.ChainID, worker *cross.Worker) bool {
-			worker.StartBackground()
-			return true
-		})
-		su.crossSafeProcessors.Range(func(_ types.ChainID, worker *cross.Worker) bool {
-			worker.StartBackground()
-			return true
-		})
-	}
-
 	return nil
 }
 
@@ -348,27 +347,10 @@ func (su *SupervisorBackend) Stop(ctx context.Context) error {
 	}
 	su.logger.Info("Closing supervisor backend")
 
-	// close all processors
-	su.chainProcessors.Range(func(id types.ChainID, processor *processors.ChainProcessor) bool {
-		su.logger.Info("stopping chain processor", "chainID", id)
-		processor.Close()
-		return true
-	})
-	su.chainProcessors.Clear()
+	su.sysCancel()
+	defer su.eventSys.Stop()
 
-	su.crossUnsafeProcessors.Range(func(id types.ChainID, worker *cross.Worker) bool {
-		su.logger.Info("stopping cross-unsafe processor", "chainID", id)
-		worker.Close()
-		return true
-	})
-	su.crossUnsafeProcessors.Clear()
-
-	su.crossSafeProcessors.Range(func(id types.ChainID, worker *cross.Worker) bool {
-		su.logger.Info("stopping cross-safe processor", "chainID", id)
-		worker.Close()
-		return true
-	})
-	su.crossSafeProcessors.Clear()
+	su.chainProcessors.Clear()
 
 	su.syncNodesController.Close()
 
@@ -557,60 +539,17 @@ func (su *SupervisorBackend) SuperRootAtTimestamp(ctx context.Context, timestamp
 	}, nil
 }
 
-// Update methods
-// ----------------------------
-
-func (su *SupervisorBackend) UpdateLocalUnsafe(ctx context.Context, chainID types.ChainID, head eth.BlockRef) error {
-	ch, ok := su.chainProcessors.Get(chainID)
-	if !ok {
-		return types.ErrUnknownChain
-	}
-	return ch.OnNewHead(head)
-}
-
-func (su *SupervisorBackend) UpdateLocalSafe(ctx context.Context, chainID types.ChainID, derivedFrom eth.BlockRef, lastDerived eth.BlockRef) error {
-	err := su.chainDBs.UpdateLocalSafe(chainID, derivedFrom, lastDerived)
-	if err != nil {
-		return err
-	}
-	su.onNewLocalSafeData()
-	return nil
-}
-
-func (su *SupervisorBackend) RecordNewL1(ctx context.Context, chain types.ChainID, ref eth.BlockRef) error {
-	return su.chainDBs.RecordNewL1(chain, ref)
-}
-
-// Access to synchronous processing for tests
-// ----------------------------
-
-func (su *SupervisorBackend) SyncEvents(chainID types.ChainID) error {
-	ch, ok := su.chainProcessors.Get(chainID)
-	if !ok {
-		return types.ErrUnknownChain
-	}
-	ch.ProcessToHead()
-	return nil
-}
-
-func (su *SupervisorBackend) SyncCrossUnsafe(chainID types.ChainID) error {
-	ch, ok := su.crossUnsafeProcessors.Get(chainID)
-	if !ok {
-		return types.ErrUnknownChain
-	}
-	return ch.ProcessWork()
+// PullLatestL1 makes the supervisor aware of the latest L1 block. Exposed for testing purposes.
+func (su *SupervisorBackend) PullLatestL1() error {
+	return su.l1Accessor.PullLatest()
 }
 
-func (su *SupervisorBackend) SyncCrossSafe(chainID types.ChainID) error {
-	ch, ok := su.crossSafeProcessors.Get(chainID)
-	if !ok {
-		return types.ErrUnknownChain
-	}
-	return ch.ProcessWork()
+// PullFinalizedL1 makes the supervisor aware of the finalized L1 block. Exposed for testing purposes.
+func (su *SupervisorBackend) PullFinalizedL1() error {
+	return su.l1Accessor.PullFinalized()
 }
 
-// SyncFinalizedL1 is a test-only method to update the finalized L1 block without the use of a subscription
-func (su *SupervisorBackend) SyncFinalizedL1(ref eth.BlockRef) {
-	fn := processors.MaybeUpdateFinalizedL1Fn(context.Background(), su.logger, su.chainDBs)
-	fn(context.Background(), ref)
+// SetConfDepthL1 changes the confirmation depth of the L1 chain that is accessible to the supervisor.
+func (su *SupervisorBackend) SetConfDepthL1(depth uint64) {
+	su.l1Accessor.SetConfDepth(depth)
 }

op-supervisor/supervisor/backend/backend_test.go

@@ -13,6 +13,7 @@ import (
 	types2 "github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/log"
 
+	"github.com/ethereum-optimism/optimism/op-node/rollup/event"
 	"github.com/ethereum-optimism/optimism/op-service/eth"
 	oplog "github.com/ethereum-optimism/optimism/op-service/log"
 	opmetrics "github.com/ethereum-optimism/optimism/op-service/metrics"
@@ -24,6 +25,7 @@ import (
 	"github.com/ethereum-optimism/optimism/op-supervisor/metrics"
 	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend/depset"
 	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend/processors"
+	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend/superevents"
 	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend/syncnode"
 	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/types"
 )
@@ -61,7 +63,8 @@ func TestBackendLifetime(t *testing.T) {
 		Datadir:               dataDir,
 	}
 
-	b, err := NewSupervisorBackend(context.Background(), logger, m, cfg)
+	ex := event.NewGlobalSynchronous(context.Background())
+	b, err := NewSupervisorBackend(context.Background(), logger, m, cfg, ex)
 	require.NoError(t, err)
 	t.Log("initialized!")
 
@@ -106,12 +109,13 @@ func TestBackendLifetime(t *testing.T) {
 
 	src.ExpectBlockRefByNumber(2, eth.L1BlockRef{}, ethereum.NotFound)
 
-	err = b.UpdateLocalUnsafe(context.Background(), chainA, blockY)
-	require.NoError(t, err)
+	b.emitter.Emit(superevents.LocalUnsafeReceivedEvent{
+		ChainID:        chainA,
+		NewLocalUnsafe: blockY,
+	})
 	// Make the processing happen, so we can rely on the new chain information,
 	// and not run into errors for future data that isn't mocked at this time.
-	proc, _ := b.chainProcessors.Get(chainA)
-	proc.ProcessToHead()
+	require.NoError(t, ex.Drain())
 
 	_, err = b.CrossUnsafe(context.Background(), chainA)
 	require.ErrorIs(t, err, types.ErrFuture, "still no data yet, need cross-unsafe")

op-supervisor/supervisor/backend/cross/safe_update.go

 package cross
 
 import (
-	"context"
 	"errors"
 	"fmt"
 
 	"github.com/ethereum/go-ethereum/log"
 
+	"github.com/ethereum-optimism/optimism/op-node/rollup/event"
 	"github.com/ethereum-optimism/optimism/op-service/eth"
+	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend/superevents"
 	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/types"
 )
 
@@ -26,7 +27,7 @@ type CrossSafeDeps interface {
 	UpdateCrossSafe(chain types.ChainID, l1View eth.BlockRef, lastCrossDerived eth.BlockRef) error
 }
 
-func CrossSafeUpdate(ctx context.Context, logger log.Logger, chainID types.ChainID, d CrossSafeDeps) error {
+func CrossSafeUpdate(logger log.Logger, chainID types.ChainID, d CrossSafeDeps) error {
 	logger.Debug("Cross-safe update call")
 	// TODO(#11693): establish L1 reorg-lock of scopeDerivedFrom
 	// defer unlock once we are done checking the chain
@@ -100,13 +101,6 @@ func scopedCrossSafeUpdate(logger log.Logger, chainID types.ChainID, d CrossSafe
 	return candidateScope, nil
 }
 
-func NewCrossSafeWorker(logger log.Logger, chainID types.ChainID, d CrossSafeDeps) *Worker {
-	logger = logger.New("chain", chainID)
-	return NewWorker(logger, func(ctx context.Context) error {
-		return CrossSafeUpdate(ctx, logger, chainID, d)
-	})
-}
-
 func sliceOfExecMsgs(execMsgs map[uint32]*types.ExecutingMessage) []*types.ExecutingMessage {
 	msgs := make([]*types.ExecutingMessage, 0, len(execMsgs))
 	for _, msg := range execMsgs {
@@ -114,3 +108,39 @@ func sliceOfExecMsgs(execMsgs map[uint32]*types.ExecutingMessage) []*types.Execu
 	}
 	return msgs
 }
+
+type CrossSafeWorker struct {
+	logger  log.Logger
+	chainID types.ChainID
+	d       CrossSafeDeps
+}
+
+func (c *CrossSafeWorker) OnEvent(ev event.Event) bool {
+	switch x := ev.(type) {
+	case superevents.UpdateCrossSafeRequestEvent:
+		if x.ChainID != c.chainID {
+			return false
+		}
+		if err := CrossSafeUpdate(c.logger, c.chainID, c.d); err != nil {
+			if errors.Is(err, types.ErrFuture) {
+				c.logger.Debug("Worker awaits additional blocks", "err", err)
+			} else {
+				c.logger.Warn("Failed to process work", "err", err)
+			}
+		}
+	default:
+		return false
+	}
+	return true
+}
+
+var _ event.Deriver = (*CrossUnsafeWorker)(nil)
+
+func NewCrossSafeWorker(logger log.Logger, chainID types.ChainID, d CrossSafeDeps) *CrossSafeWorker {
+	logger = logger.New("chain", chainID)
+	return &CrossSafeWorker{
+		logger:  logger,
+		chainID: chainID,
+		d:       d,
+	}
+}

op-supervisor/supervisor/backend/cross/safe_update_test.go

 package cross
 
 import (
-	"context"
 	"errors"
 	"testing"
 
@@ -16,7 +15,6 @@ import (
 
 func TestCrossSafeUpdate(t *testing.T) {
 	t.Run("scopedCrossSafeUpdate passes", func(t *testing.T) {
-		ctx := context.Background()
 		logger := testlog.Logger(t, log.LevelDebug)
 		chainID := types.ChainIDFromUInt64(0)
 		csd := &mockCrossSafeDeps{}
@@ -36,11 +34,10 @@ func TestCrossSafeUpdate(t *testing.T) {
 		csd.deps = mockDependencySet{}
 		// when scopedCrossSafeUpdate returns no error,
 		// no error is returned
-		err := CrossSafeUpdate(ctx, logger, chainID, csd)
+		err := CrossSafeUpdate(logger, chainID, csd)
 		require.NoError(t, err)
 	})
 	t.Run("scopedCrossSafeUpdate returns error", func(t *testing.T) {
-		ctx := context.Background()
 		logger := testlog.Logger(t, log.LevelDebug)
 		chainID := types.ChainIDFromUInt64(0)
 		csd := &mockCrossSafeDeps{}
@@ -56,11 +53,10 @@ func TestCrossSafeUpdate(t *testing.T) {
 		// when scopedCrossSafeUpdate returns an error,
 		// (by way of OpenBlock returning an error),
 		// the error is returned
-		err := CrossSafeUpdate(ctx, logger, chainID, csd)
+		err := CrossSafeUpdate(logger, chainID, csd)
 		require.ErrorContains(t, err, "some error")
 	})
 	t.Run("scopedCrossSafeUpdate returns ErrOutOfScope", func(t *testing.T) {
-		ctx := context.Background()
 		logger := testlog.Logger(t, log.LevelDebug)
 		chainID := types.ChainIDFromUInt64(0)
 		csd := &mockCrossSafeDeps{}
@@ -98,7 +94,7 @@ func TestCrossSafeUpdate(t *testing.T) {
 		// CrossSafeUpdate proceeds anyway and calls UpdateCrossSafe
 		// the update uses the new scope returned by NextDerivedFrom
 		// and a crossSafeRef made from the current crossSafe and its parent
-		err := CrossSafeUpdate(ctx, logger, chainID, csd)
+		err := CrossSafeUpdate(logger, chainID, csd)
 		require.NoError(t, err)
 		require.Equal(t, chainID, updatingChain)
 		require.Equal(t, newScope, updatingCandidateScope)
@@ -106,7 +102,6 @@ func TestCrossSafeUpdate(t *testing.T) {
 		require.Equal(t, crossSafeRef, updatingCandidate)
 	})
 	t.Run("NextDerivedFrom returns error", func(t *testing.T) {
-		ctx := context.Background()
 		logger := testlog.Logger(t, log.LevelDebug)
 		chainID := types.ChainIDFromUInt64(0)
 		csd := &mockCrossSafeDeps{}
@@ -125,11 +120,10 @@ func TestCrossSafeUpdate(t *testing.T) {
 		// when scopedCrossSafeUpdate returns Out of Scope error,
 		// and NextDerivedFrom returns an error,
 		// the error is returned
-		err := CrossSafeUpdate(ctx, logger, chainID, csd)
+		err := CrossSafeUpdate(logger, chainID, csd)
 		require.ErrorContains(t, err, "some error")
 	})
 	t.Run("PreviousDerived returns error", func(t *testing.T) {
-		ctx := context.Background()
 		logger := testlog.Logger(t, log.LevelDebug)
 		chainID := types.ChainIDFromUInt64(0)
 		csd := &mockCrossSafeDeps{}
@@ -148,11 +142,10 @@ func TestCrossSafeUpdate(t *testing.T) {
 		// when scopedCrossSafeUpdate returns Out of Scope error,
 		// and PreviousDerived returns an error,
 		// the error is returned
-		err := CrossSafeUpdate(ctx, logger, chainID, csd)
+		err := CrossSafeUpdate(logger, chainID, csd)
 		require.ErrorContains(t, err, "some error")
 	})
 	t.Run("UpdateCrossSafe returns error", func(t *testing.T) {
-		ctx := context.Background()
 		logger := testlog.Logger(t, log.LevelDebug)
 		chainID := types.ChainIDFromUInt64(0)
 		csd := &mockCrossSafeDeps{}
@@ -171,7 +164,7 @@ func TestCrossSafeUpdate(t *testing.T) {
 		// when scopedCrossSafeUpdate returns Out of Scope error,
 		// and UpdateCrossSafe returns an error,
 		// the error is returned
-		err := CrossSafeUpdate(ctx, logger, chainID, csd)
+		err := CrossSafeUpdate(logger, chainID, csd)
 		require.ErrorContains(t, err, "some error")
 	})
 }

op-supervisor/supervisor/backend/cross/unsafe_update.go

 package cross
 
 import (
-	"context"
 	"errors"
 	"fmt"
 
 	"github.com/ethereum/go-ethereum/log"
 
+	"github.com/ethereum-optimism/optimism/op-node/rollup/event"
 	"github.com/ethereum-optimism/optimism/op-service/eth"
+	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend/superevents"
 	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/types"
 )
 
@@ -22,7 +23,7 @@ type CrossUnsafeDeps interface {
 	UpdateCrossUnsafe(chain types.ChainID, crossUnsafe types.BlockSeal) error
 }
 
-func CrossUnsafeUpdate(ctx context.Context, logger log.Logger, chainID types.ChainID, d CrossUnsafeDeps) error {
+func CrossUnsafeUpdate(logger log.Logger, chainID types.ChainID, d CrossUnsafeDeps) error {
 	var candidate types.BlockSeal
 	var execMsgs []*types.ExecutingMessage
 
@@ -71,9 +72,38 @@ func CrossUnsafeUpdate(ctx context.Context, logger log.Logger, chainID types.Cha
 	return nil
 }
 
-func NewCrossUnsafeWorker(logger log.Logger, chainID types.ChainID, d CrossUnsafeDeps) *Worker {
+type CrossUnsafeWorker struct {
+	logger  log.Logger
+	chainID types.ChainID
+	d       CrossUnsafeDeps
+}
+
+func (c *CrossUnsafeWorker) OnEvent(ev event.Event) bool {
+	switch x := ev.(type) {
+	case superevents.UpdateCrossUnsafeRequestEvent:
+		if x.ChainID != c.chainID {
+			return false
+		}
+		if err := CrossUnsafeUpdate(c.logger, c.chainID, c.d); err != nil {
+			if errors.Is(err, types.ErrFuture) {
+				c.logger.Debug("Worker awaits additional blocks", "err", err)
+			} else {
+				c.logger.Warn("Failed to process work", "err", err)
+			}
+		}
+	default:
+		return false
+	}
+	return true
+}
+
+var _ event.Deriver = (*CrossUnsafeWorker)(nil)
+
+func NewCrossUnsafeWorker(logger log.Logger, chainID types.ChainID, d CrossUnsafeDeps) *CrossUnsafeWorker {
 	logger = logger.New("chain", chainID)
-	return NewWorker(logger, func(ctx context.Context) error {
-		return CrossUnsafeUpdate(ctx, logger, chainID, d)
-	})
+	return &CrossUnsafeWorker{
+		logger:  logger,
+		chainID: chainID,
+		d:       d,
+	}
 }

op-supervisor/supervisor/backend/cross/unsafe_update_test.go

 package cross
 
 import (
-	"context"
 	"errors"
 	"testing"
 
@@ -16,7 +15,6 @@ import (
 
 func TestCrossUnsafeUpdate(t *testing.T) {
 	t.Run("CrossUnsafe returns error", func(t *testing.T) {
-		ctx := context.Background()
 		logger := testlog.Logger(t, log.LevelDebug)
 		chainID := types.ChainIDFromUInt64(0)
 		usd := &mockCrossUnsafeDeps{}
@@ -26,11 +24,10 @@ func TestCrossUnsafeUpdate(t *testing.T) {
 		usd.deps = mockDependencySet{}
 		// when an error is returned by CrossUnsafe,
 		// the error is returned
-		err := CrossUnsafeUpdate(ctx, logger, chainID, usd)
+		err := CrossUnsafeUpdate(logger, chainID, usd)
 		require.ErrorContains(t, err, "some error")
 	})
 	t.Run("CrossUnsafe returns ErrFuture", func(t *testing.T) {
-		ctx := context.Background()
 		logger := testlog.Logger(t, log.LevelDebug)
 		chainID := types.ChainIDFromUInt64(0)
 		usd := &mockCrossUnsafeDeps{}
@@ -40,11 +37,10 @@ func TestCrossUnsafeUpdate(t *testing.T) {
 		usd.deps = mockDependencySet{}
 		// when a ErrFuture is returned by CrossUnsafe,
 		// no error is returned
-		err := CrossUnsafeUpdate(ctx, logger, chainID, usd)
+		err := CrossUnsafeUpdate(logger, chainID, usd)
 		require.NoError(t, err)
 	})
 	t.Run("OpenBlock returns error", func(t *testing.T) {
-		ctx := context.Background()
 		logger := testlog.Logger(t, log.LevelDebug)
 		chainID := types.ChainIDFromUInt64(0)
 		usd := &mockCrossUnsafeDeps{}
@@ -54,11 +50,10 @@ func TestCrossUnsafeUpdate(t *testing.T) {
 		usd.deps = mockDependencySet{}
 		// when an error is returned by OpenBlock,
 		// the error is returned
-		err := CrossUnsafeUpdate(ctx, logger, chainID, usd)
+		err := CrossUnsafeUpdate(logger, chainID, usd)
 		require.ErrorContains(t, err, "some error")
 	})
 	t.Run("opened block parent hash does not match", func(t *testing.T) {
-		ctx := context.Background()
 		logger := testlog.Logger(t, log.LevelDebug)
 		chainID := types.ChainIDFromUInt64(0)
 		usd := &mockCrossUnsafeDeps{}
@@ -73,11 +68,10 @@ func TestCrossUnsafeUpdate(t *testing.T) {
 		usd.deps = mockDependencySet{}
 		// when the parent hash of the opened block does not match the cross-unsafe block,
 		// an ErrConflict is returned
-		err := CrossUnsafeUpdate(ctx, logger, chainID, usd)
+		err := CrossUnsafeUpdate(logger, chainID, usd)
 		require.ErrorIs(t, err, types.ErrConflict)
 	})
 	t.Run("CrossSafeHazards returns error", func(t *testing.T) {
-		ctx := context.Background()
 		logger := testlog.Logger(t, log.LevelDebug)
 		chainID := types.ChainIDFromUInt64(0)
 		usd := &mockCrossUnsafeDeps{}
@@ -97,11 +91,10 @@ func TestCrossUnsafeUpdate(t *testing.T) {
 		}
 		// when CrossSafeHazards returns an error,
 		// the error is returned
-		err := CrossUnsafeUpdate(ctx, logger, chainID, usd)
+		err := CrossUnsafeUpdate(logger, chainID, usd)
 		require.ErrorContains(t, err, "some error")
 	})
 	t.Run("HazardUnsafeFrontierChecks returns error", func(t *testing.T) {
-		ctx := context.Background()
 		logger := testlog.Logger(t, log.LevelDebug)
 		chainID := types.ChainIDFromUInt64(0)
 		usd := &mockCrossUnsafeDeps{}
@@ -128,11 +121,10 @@ func TestCrossUnsafeUpdate(t *testing.T) {
 		}
 		// when HazardUnsafeFrontierChecks returns an error,
 		// the error is returned
-		err := CrossUnsafeUpdate(ctx, logger, chainID, usd)
+		err := CrossUnsafeUpdate(logger, chainID, usd)
 		require.ErrorContains(t, err, "some error")
 	})
 	t.Run("HazardCycleChecks returns error", func(t *testing.T) {
-		ctx := context.Background()
 		logger := testlog.Logger(t, log.LevelDebug)
 		chainID := types.ChainIDFromUInt64(0)
 		usd := &mockCrossUnsafeDeps{}
@@ -152,12 +144,11 @@ func TestCrossUnsafeUpdate(t *testing.T) {
 		usd.deps = mockDependencySet{}
 
 		// HazardCycleChecks returns an error with appropriate wrapping
-		err := CrossUnsafeUpdate(ctx, logger, chainID, usd)
+		err := CrossUnsafeUpdate(logger, chainID, usd)
 		require.ErrorContains(t, err, "cycle detected")
 		require.ErrorContains(t, err, "failed to verify block")
 	})
 	t.Run("successful update", func(t *testing.T) {
-		ctx := context.Background()
 		logger := testlog.Logger(t, log.LevelDebug)
 		chainID := types.ChainIDFromUInt64(0)
 		usd := &mockCrossUnsafeDeps{}
@@ -181,7 +172,7 @@ func TestCrossUnsafeUpdate(t *testing.T) {
 		}
 		// when there are no errors, the cross-unsafe block is updated
 		// the updated block is the block opened in OpenBlock
-		err := CrossUnsafeUpdate(ctx, logger, chainID, usd)
+		err := CrossUnsafeUpdate(logger, chainID, usd)
 		require.NoError(t, err)
 		require.Equal(t, chainID, updatingChainID)
 		require.Equal(t, types.BlockSealFromRef(bl), updatingBlock)

op-supervisor/supervisor/backend/cross/worker.go

-package cross
-
-import (
-	"context"
-	"errors"
-	"sync"
-	"time"
-
-	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/types"
-	"github.com/ethereum/go-ethereum/log"
-)
-
-// Worker iterates work
-type Worker struct {
-	log log.Logger
-
-	// workFn is the function to call to process the scope
-	workFn workFn
-
-	// channel with capacity of 1, full if there is work to do
-	poke         chan struct{}
-	pollDuration time.Duration
-
-	// lifetime management of the chain processor
-	ctx    context.Context
-	cancel context.CancelFunc
-	wg     sync.WaitGroup
-}
-
-// workFn is a function used by the worker
-// it is opaque to the worker, and is set by the constructor
-type workFn func(ctx context.Context) error
-
-// NewWorker creates a new worker to process updates
-func NewWorker(log log.Logger, workFn workFn) *Worker {
-	ctx, cancel := context.WithCancel(context.Background())
-	out := &Worker{
-		log:  log,
-		poke: make(chan struct{}, 1),
-		// The data may have changed, and we may have missed a poke, so re-attempt regularly.
-		pollDuration: 250 * time.Millisecond,
-		ctx:          ctx,
-		cancel:       cancel,
-	}
-	out.workFn = workFn
-	return out
-}
-
-func (s *Worker) StartBackground() {
-	s.wg.Add(1)
-	go s.worker()
-}
-
-func (s *Worker) ProcessWork() error {
-	return s.workFn(s.ctx)
-}
-
-func (s *Worker) worker() {
-	defer s.wg.Done()
-
-	delay := time.NewTicker(s.pollDuration)
-	for {
-		if s.ctx.Err() != nil { // check if we are closing down
-			return
-		}
-
-		// do the work
-		err := s.workFn(s.ctx)
-		if err != nil {
-			if errors.Is(err, s.ctx.Err()) {
-				return
-			}
-			if errors.Is(err, types.ErrFuture) {
-				s.log.Debug("Worker awaits additional blocks", "err", err)
-			} else {
-				s.log.Warn("Failed to process work", "err", err)
-			}
-		}
-
-		// await next time we process, or detect shutdown
-		select {
-		case <-s.ctx.Done():
-			delay.Stop()
-			return
-		case <-s.poke:
-			s.log.Debug("Continuing cross-safe verification after hint of new data")
-			continue
-		case <-delay.C:
-			s.log.Debug("Checking for cross-safe updates")
-			continue
-		}
-	}
-}
-
-func (s *Worker) OnNewData() {
-	// signal that we have something to process
-	select {
-	case s.poke <- struct{}{}:
-	default:
-		// already requested an update
-	}
-}
-
-func (s *Worker) Close() {
-	s.cancel()
-	s.wg.Wait()
-}

op-supervisor/supervisor/backend/cross/worker_test.go

-package cross
-
-import (
-	"context"
-	"sync/atomic"
-	"testing"
-	"time"
-
-	"github.com/ethereum-optimism/optimism/op-service/testlog"
-	"github.com/ethereum/go-ethereum/log"
-	"github.com/stretchr/testify/require"
-)
-
-func TestWorker(t *testing.T) {
-	logger := testlog.Logger(t, log.LevelDebug)
-	t.Run("do work", func(t *testing.T) {
-		var count int32
-		w := NewWorker(logger, func(ctx context.Context) error {
-			atomic.AddInt32(&count, 1)
-			return nil
-		})
-		t.Cleanup(w.Close)
-		// when ProcessWork is called, the workFn is called once
-		require.NoError(t, w.ProcessWork())
-		require.EqualValues(t, 1, atomic.LoadInt32(&count))
-	})
-	t.Run("background worker", func(t *testing.T) {
-		var count int32
-		w := NewWorker(logger, func(ctx context.Context) error {
-			atomic.AddInt32(&count, 1)
-			return nil
-		})
-		t.Cleanup(w.Close)
-		// set a long poll duration so the worker does not auto-run
-		w.pollDuration = 100 * time.Second
-		// when StartBackground is called, the worker runs in the background
-		// the count should increment once
-		w.StartBackground()
-		require.Eventually(t, func() bool {
-			return atomic.LoadInt32(&count) == 1
-		}, 2*time.Second, 100*time.Millisecond)
-	})
-	t.Run("background worker OnNewData", func(t *testing.T) {
-		var count int32
-		w := NewWorker(logger, func(ctx context.Context) error {
-			atomic.AddInt32(&count, 1)
-			return nil
-		})
-		t.Cleanup(w.Close)
-		// set a long poll duration so the worker does not auto-run
-		w.pollDuration = 100 * time.Second
-		// when StartBackground is called, the worker runs in the background
-		// the count should increment once
-		w.StartBackground()
-		require.Eventually(t, func() bool {
-			return atomic.LoadInt32(&count) == 1
-		}, 2*time.Second, 100*time.Millisecond)
-		// when OnNewData is called, the worker runs again
-		w.OnNewData()
-		require.Eventually(t, func() bool {
-			return atomic.LoadInt32(&count) == 2
-		}, 2*time.Second, 100*time.Millisecond)
-		// and due to the long poll duration, the worker does not run again
-		require.Never(t, func() bool {
-			return atomic.LoadInt32(&count) > 2
-		}, time.Second, 100*time.Millisecond)
-	})
-	t.Run("background fast poll", func(t *testing.T) {
-		var count int32
-		w := NewWorker(logger, func(ctx context.Context) error {
-			atomic.AddInt32(&count, 1)
-			return nil
-		})
-		t.Cleanup(w.Close)
-		// set a long poll duration so the worker does not auto-run
-		w.pollDuration = 100 * time.Millisecond
-		// when StartBackground is called, the worker runs in the background
-		// the count should increment rapidly and reach at least 10 in 1 second
-		w.StartBackground()
-		require.Eventually(t, func() bool {
-			return atomic.LoadInt32(&count) >= 10
-		}, 2*time.Second, 100*time.Millisecond)
-	})
-	t.Run("close", func(t *testing.T) {
-		var count int32
-		w := NewWorker(logger, func(ctx context.Context) error {
-			atomic.AddInt32(&count, 1)
-			return nil
-		})
-		t.Cleanup(w.Close) // close on cleanup in case of early error
-		// set a long poll duration so the worker does not auto-run
-		w.pollDuration = 100 * time.Millisecond
-		// when StartBackground is called, the worker runs in the background
-		// the count should increment rapidly and reach at least 10 in 1 second
-		w.StartBackground()
-		require.Eventually(t, func() bool {
-			return atomic.LoadInt32(&count) >= 10
-		}, 10*time.Second, time.Second)
-		// once the worker is closed, it stops running
-		// and the count does not increment
-		w.Close()
-		stopCount := atomic.LoadInt32(&count)
-		require.Never(t, func() bool {
-			return atomic.LoadInt32(&count) != stopCount
-		}, time.Second, 100*time.Millisecond)
-	})
-}

op-supervisor/supervisor/backend/db/anchor.go

+package db
+
+import (
+	"errors"
+
+	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/types"
+)
+
+// maybeInitSafeDB initializes the chain database if it is not already initialized
+// it checks if the Local Safe database is empty, and loads it with the Anchor Point if so
+func (db *ChainsDB) maybeInitSafeDB(id types.ChainID, anchor types.DerivedBlockRefPair) {
+	_, err := db.LocalSafe(id)
+	if errors.Is(err, types.ErrFuture) {
+		db.logger.Debug("initializing chain database", "chain", id)
+		if err := db.UpdateCrossSafe(id, anchor.DerivedFrom, anchor.Derived); err != nil {
+			db.logger.Warn("failed to initialize cross safe", "chain", id, "error", err)
+		}
+		db.UpdateLocalSafe(id, anchor.DerivedFrom, anchor.Derived)
+	} else if err != nil {
+		db.logger.Warn("failed to check if chain database is initialized", "chain", id, "error", err)
+	} else {
+		db.logger.Debug("chain database already initialized", "chain", id)
+	}
+}
+
+func (db *ChainsDB) maybeInitEventsDB(id types.ChainID, anchor types.DerivedBlockRefPair) {
+	_, _, _, err := db.OpenBlock(id, 0)
+	if errors.Is(err, types.ErrFuture) {
+		db.logger.Debug("initializing events database", "chain", id)
+		err := db.SealBlock(id, anchor.Derived)
+		if err != nil {
+			db.logger.Warn("failed to seal initial block", "chain", id, "error", err)
+		}
+		db.logger.Debug("initialized events database", "chain", id)
+	} else if err != nil {
+		db.logger.Warn("failed to check if logDB is initialized", "chain", id, "error", err)
+	} else {
+		db.logger.Debug("events database already initialized", "chain", id)
+	}
+}

op-supervisor/supervisor/backend/db/db.go

@@ -8,13 +8,14 @@ import (
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/log"
 
+	"github.com/ethereum-optimism/optimism/op-node/rollup/event"
 	"github.com/ethereum-optimism/optimism/op-service/eth"
 	"github.com/ethereum-optimism/optimism/op-service/locks"
 	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend/db/fromda"
 	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend/db/logs"
 	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend/depset"
+	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend/superevents"
 	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/types"
-	gethevent "github.com/ethereum/go-ethereum/event"
 )
 
 type LogStorage interface {
@@ -87,12 +88,6 @@ type ChainsDB struct {
 	// cross-safe: index of L2 blocks we know to only have cross-L2 valid dependencies
 	crossDBs locks.RWMap[types.ChainID, CrossDerivedFromStorage]
 
-	localUnsafeFeeds locks.RWMap[types.ChainID, *gethevent.FeedOf[types.BlockSeal]]
-	crossUnsafeFeeds locks.RWMap[types.ChainID, *gethevent.FeedOf[types.BlockSeal]]
-	localSafeFeeds   locks.RWMap[types.ChainID, *gethevent.FeedOf[types.DerivedBlockSealPair]]
-	crossSafeFeeds   locks.RWMap[types.ChainID, *gethevent.FeedOf[types.DerivedBlockSealPair]]
-	l2FinalityFeeds  locks.RWMap[types.ChainID, *gethevent.FeedOf[types.BlockSeal]]
-
 	// finalized: the L1 finality progress. This can be translated into what may be considered as finalized in L2.
 	// It is initially zeroed, and the L2 finality query will return
 	// an error until it has this L1 finality to work with.
@@ -103,8 +98,13 @@ type ChainsDB struct {
 	depSet depset.DependencySet
 
 	logger log.Logger
+
+	// emitter used to signal when the DB changes, for other modules to react to
+	emitter event.Emitter
 }
 
+var _ event.AttachEmitter = (*ChainsDB)(nil)
+
 func NewChainsDB(l log.Logger, depSet depset.DependencySet) *ChainsDB {
 	return &ChainsDB{
 		logger: l,
@@ -112,6 +112,25 @@ func NewChainsDB(l log.Logger, depSet depset.DependencySet) *ChainsDB {
 	}
 }
 
+func (db *ChainsDB) AttachEmitter(em event.Emitter) {
+	db.emitter = em
+}
+
+func (db *ChainsDB) OnEvent(ev event.Event) bool {
+	switch x := ev.(type) {
+	case superevents.AnchorEvent:
+		db.maybeInitEventsDB(x.ChainID, x.Anchor)
+		db.maybeInitSafeDB(x.ChainID, x.Anchor)
+	case superevents.LocalDerivedEvent:
+		db.UpdateLocalSafe(x.ChainID, x.Derived.DerivedFrom, x.Derived.Derived)
+	case superevents.FinalizedL1RequestEvent:
+		db.onFinalizedL1(x.FinalizedL1)
+	default:
+		return false
+	}
+	return true
+}
+
 func (db *ChainsDB) AddLogDB(chainID types.ChainID, logDB LogStorage) {
 	if db.logDBs.Has(chainID) {
 		db.logger.Warn("overwriting existing log DB for chain", "chain", chainID)
@@ -143,14 +162,6 @@ func (db *ChainsDB) AddCrossUnsafeTracker(chainID types.ChainID) {
 	db.crossUnsafe.Set(chainID, &locks.RWValue[types.BlockSeal]{})
 }
 
-func (db *ChainsDB) AddSubscriptions(chainID types.ChainID) {
-	locks.InitPtrMaybe(&db.l2FinalityFeeds, chainID)
-	locks.InitPtrMaybe(&db.crossSafeFeeds, chainID)
-	locks.InitPtrMaybe(&db.localSafeFeeds, chainID)
-	locks.InitPtrMaybe(&db.crossUnsafeFeeds, chainID)
-	locks.InitPtrMaybe(&db.localUnsafeFeeds, chainID)
-}
-
 // ResumeFromLastSealedBlock prepares the chains db to resume recording events after a restart.
 // It rewinds the database to the last block that is guaranteed to have been fully recorded to the database,
 // to ensure it can resume recording from the first log of the next block.

op-supervisor/supervisor/backend/db/feeds.go

-package db
-
-import (
-	"fmt"
-
-	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/types"
-	gethevent "github.com/ethereum/go-ethereum/event"
-)
-
-func (db *ChainsDB) SubscribeLocalUnsafe(chainID types.ChainID, c chan<- types.BlockSeal) (gethevent.Subscription, error) {
-	sub, ok := db.localUnsafeFeeds.Get(chainID)
-	if !ok {
-		return nil, fmt.Errorf("cannot subscribe to local-unsafe: %w: %s", types.ErrUnknownChain, chainID)
-	}
-	return sub.Subscribe(c), nil
-}
-
-func (db *ChainsDB) SubscribeCrossUnsafe(chainID types.ChainID, c chan<- types.BlockSeal) (gethevent.Subscription, error) {
-	sub, ok := db.localUnsafeFeeds.Get(chainID)
-	if !ok {
-		return nil, fmt.Errorf("cannot subscribe to cross-unsafe: %w: %s", types.ErrUnknownChain, chainID)
-	}
-	return sub.Subscribe(c), nil
-}
-
-func (db *ChainsDB) SubscribeLocalSafe(chainID types.ChainID, c chan<- types.DerivedBlockSealPair) (gethevent.Subscription, error) {
-	sub, ok := db.localSafeFeeds.Get(chainID)
-	if !ok {
-		return nil, fmt.Errorf("cannot subscribe to cross-safe: %w: %s", types.ErrUnknownChain, chainID)
-	}
-	return sub.Subscribe(c), nil
-}
-
-func (db *ChainsDB) SubscribeCrossSafe(chainID types.ChainID, c chan<- types.DerivedBlockSealPair) (gethevent.Subscription, error) {
-	sub, ok := db.crossSafeFeeds.Get(chainID)
-	if !ok {
-		return nil, fmt.Errorf("cannot subscribe to cross-safe: %w: %s", types.ErrUnknownChain, chainID)
-	}
-	return sub.Subscribe(c), nil
-}
-
-func (db *ChainsDB) SubscribeFinalized(chainID types.ChainID, c chan<- types.BlockSeal) (gethevent.Subscription, error) {
-	sub, ok := db.l2FinalityFeeds.Get(chainID)
-	if !ok {
-		return nil, fmt.Errorf("cannot subscribe to finalized: %w: %s", types.ErrUnknownChain, chainID)
-	}
-	return sub.Subscribe(c), nil
-}

op-supervisor/supervisor/backend/db/update.go

 package db
 
 import (
-	"errors"
 	"fmt"
 
 	"github.com/ethereum/go-ethereum/common"
 
 	"github.com/ethereum-optimism/optimism/op-service/eth"
+	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend/superevents"
 	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/types"
 )
 
@@ -33,10 +33,10 @@ func (db *ChainsDB) SealBlock(chain types.ChainID, block eth.BlockRef) error {
 		return fmt.Errorf("failed to seal block %v: %w", block, err)
 	}
 	db.logger.Info("Updated local unsafe", "chain", chain, "block", block)
-	feed, ok := db.localUnsafeFeeds.Get(chain)
-	if ok {
-		feed.Send(types.BlockSealFromRef(block))
-	}
+	db.emitter.Emit(superevents.LocalUnsafeUpdateEvent{
+		ChainID:        chain,
+		NewLocalUnsafe: block,
+	})
 	return nil
 }
 
@@ -48,23 +48,31 @@ func (db *ChainsDB) Rewind(chain types.ChainID, headBlockNum uint64) error {
 	return logDB.Rewind(headBlockNum)
 }
 
-func (db *ChainsDB) UpdateLocalSafe(chain types.ChainID, derivedFrom eth.BlockRef, lastDerived eth.BlockRef) error {
+func (db *ChainsDB) UpdateLocalSafe(chain types.ChainID, derivedFrom eth.BlockRef, lastDerived eth.BlockRef) {
+	logger := db.logger.New("chain", chain, "derivedFrom", derivedFrom, "lastDerived", lastDerived)
 	localDB, ok := db.localDBs.Get(chain)
 	if !ok {
-		return fmt.Errorf("cannot UpdateLocalSafe: %w: %v", types.ErrUnknownChain, chain)
+		logger.Error("Cannot update local-safe DB, unknown chain")
+		return
 	}
-	db.logger.Debug("Updating local safe", "chain", chain, "derivedFrom", derivedFrom, "lastDerived", lastDerived)
+	logger.Debug("Updating local safe DB")
 	if err := localDB.AddDerived(derivedFrom, lastDerived); err != nil {
-		return err
+		db.logger.Warn("Failed to update local safe")
+		db.emitter.Emit(superevents.LocalSafeOutOfSyncEvent{
+			ChainID: chain,
+			L1Ref:   derivedFrom,
+			Err:     err,
+		})
+		return
 	}
-	feed, ok := db.localSafeFeeds.Get(chain)
-	if ok {
-		feed.Send(types.DerivedBlockSealPair{
+	db.logger.Info("Updated local safe DB")
+	db.emitter.Emit(superevents.LocalSafeUpdateEvent{
+		ChainID: chain,
+		NewLocalSafe: types.DerivedBlockSealPair{
 			DerivedFrom: types.BlockSealFromRef(derivedFrom),
 			Derived:     types.BlockSealFromRef(lastDerived),
-		})
-	}
-	return nil
+		},
+	})
 }
 
 func (db *ChainsDB) UpdateCrossUnsafe(chain types.ChainID, crossUnsafe types.BlockSeal) error {
@@ -73,11 +81,11 @@ func (db *ChainsDB) UpdateCrossUnsafe(chain types.ChainID, crossUnsafe types.Blo
 		return fmt.Errorf("cannot UpdateCrossUnsafe: %w: %s", types.ErrUnknownChain, chain)
 	}
 	v.Set(crossUnsafe)
-	feed, ok := db.crossUnsafeFeeds.Get(chain)
-	if ok {
-		feed.Send(crossUnsafe)
-	}
 	db.logger.Info("Updated cross-unsafe", "chain", chain, "crossUnsafe", crossUnsafe)
+	db.emitter.Emit(superevents.CrossUnsafeUpdateEvent{
+		ChainID:        chain,
+		NewCrossUnsafe: crossUnsafe,
+	})
 	return nil
 }
 
@@ -90,89 +98,40 @@ func (db *ChainsDB) UpdateCrossSafe(chain types.ChainID, l1View eth.BlockRef, la
 		return err
 	}
 	db.logger.Info("Updated cross-safe", "chain", chain, "l1View", l1View, "lastCrossDerived", lastCrossDerived)
-	// notify subscribers
-	sub, ok := db.crossSafeFeeds.Get(chain)
-	if ok {
-		sub.Send(types.DerivedBlockSealPair{
+	db.emitter.Emit(superevents.CrossSafeUpdateEvent{
+		ChainID: chain,
+		NewCrossSafe: types.DerivedBlockSealPair{
 			DerivedFrom: types.BlockSealFromRef(l1View),
 			Derived:     types.BlockSealFromRef(lastCrossDerived),
-		})
-	}
+		},
+	})
 	return nil
 }
 
-func (db *ChainsDB) UpdateFinalizedL1(finalized eth.BlockRef) error {
+func (db *ChainsDB) onFinalizedL1(finalized eth.BlockRef) {
 	// Lock, so we avoid race-conditions in-between getting (for comparison) and setting.
 	// Unlock is managed explicitly, in this function so we can call NotifyL2Finalized after releasing the lock.
 	db.finalizedL1.Lock()
 
-	if v := db.finalizedL1.Value; v.Number > finalized.Number {
+	if v := db.finalizedL1.Value; v != (eth.BlockRef{}) && v.Number > finalized.Number {
 		db.finalizedL1.Unlock()
-		return fmt.Errorf("cannot rewind finalized L1 head from %s to %s", v, finalized)
+		db.logger.Warn("Cannot rewind finalized L1 block", "current", v, "signal", finalized)
+		return
 	}
 	db.finalizedL1.Value = finalized
 	db.logger.Info("Updated finalized L1", "finalizedL1", finalized)
 	db.finalizedL1.Unlock()
 
-	// whenver the L1 Finalized changes, the L2 Finalized may change, notify subscribers
+	db.emitter.Emit(superevents.FinalizedL1UpdateEvent{
+		FinalizedL1: finalized,
+	})
+	// whenever the L1 Finalized changes, the L2 Finalized may change, notify subscribers
 	for _, chain := range db.depSet.Chains() {
-		db.NotifyL2Finalized(chain)
-	}
-
-	return nil
-}
-
-// NotifyL2Finalized notifies all L2 finality subscribers of the latest L2 finalized block for the given chain.
-func (db *ChainsDB) NotifyL2Finalized(chain types.ChainID) {
-	f, err := db.Finalized(chain)
-	if err != nil {
-		db.logger.Error("Failed to get finalized L1 block", "chain", chain, "err", err)
-		return
-	}
-	sub, ok := db.l2FinalityFeeds.Get(chain)
-	if ok {
-		sub.Send(f)
-	}
-}
-
-// RecordNewL1 records a new L1 block in the database for a given chain.
-// It uses the latest derived L2 block as the derived block for the new L1 block.
-// It also triggers L2 Finality Notifications, as a new L1 may change L2 finality.
-// NOTE: callers to this function are responsible for ensuring that advancing the L1 block is correct
-// (ie that no further L2 blocks need to be recorded) because if the L1 block is recorded with a gap in derived blocks,
-// the database is considered corrupted and the supervisor will not be able to proceed without pruning the database.
-// The database cannot protect against this because it is does not know how many L2 blocks to expect for a given L1 block.
-func (db *ChainsDB) RecordNewL1(chain types.ChainID, ref eth.BlockRef) error {
-	// get local derivation database
-	ldb, ok := db.localDBs.Get(chain)
-	if !ok {
-		return fmt.Errorf("cannot RecordNewL1 to chain %s: %w", chain, types.ErrUnknownChain)
+		fin, err := db.Finalized(chain)
+		if err != nil {
+			db.logger.Warn("Unable to determine finalized L2 block", "chain", chain, "l1Finalized", finalized)
+			continue
+		}
+		db.emitter.Emit(superevents.FinalizedL2UpdateEvent{ChainID: chain, FinalizedL2: fin})
 	}
-	// get the latest derived and derivedFrom blocks
-	derivedFrom, derived, err := ldb.Latest()
-	if err != nil {
-		return fmt.Errorf("failed to get latest derivedFrom for chain %s: %w", chain, err)
-	}
-	// make a ref from the latest derived block
-	derivedParent, err := ldb.PreviousDerived(derived.ID())
-	if errors.Is(err, types.ErrFuture) {
-		db.logger.Warn("Empty DB, Recording first L1 block", "chain", chain, "err", err)
-	} else if err != nil {
-		db.logger.Warn("Failed to get latest derivedfrom to insert new L1 block", "chain", chain, "err", err)
-		return err
-	}
-	derivedRef := derived.MustWithParent(derivedParent.ID())
-	// don't push the new L1 block if it's not newer than the latest derived block
-	if derivedFrom.Number >= ref.Number {
-		db.logger.Warn("L1 block has already been processed for this height", "chain", chain, "block", ref, "latest", derivedFrom)
-		return nil
-	}
-	// the database is extended with the new L1 and the existing L2
-	if err = db.UpdateLocalSafe(chain, ref, derivedRef); err != nil {
-		db.logger.Error("Failed to update local safe", "chain", chain, "block", ref, "derived", derived, "err", err)
-		return err
-	}
-	// now tht the db has the new L1, we can attempt to to notify the L2 finality subscribers
-	db.NotifyL2Finalized(chain)
-	return nil
 }

op-supervisor/supervisor/backend/executor.go

+package backend
+
+type Executor interface {
+	Start()
+}

op-supervisor/supervisor/backend/l1access/l1_accessor.go

@@ -3,14 +3,20 @@ package l1access
 import (
 	"context"
 	"errors"
+	"fmt"
 	"sync"
 	"time"
 
-	"github.com/ethereum-optimism/optimism/op-service/eth"
 	"github.com/ethereum/go-ethereum"
 	"github.com/ethereum/go-ethereum/log"
+
+	"github.com/ethereum-optimism/optimism/op-node/rollup/event"
+	"github.com/ethereum-optimism/optimism/op-service/eth"
+	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend/superevents"
 )
 
+const reqTimeout = time.Second * 10
+
 type L1Source interface {
 	L1BlockRefByNumber(ctx context.Context, number uint64) (eth.L1BlockRef, error)
 	L1BlockRefByLabel(ctx context.Context, label eth.BlockLabel) (eth.L1BlockRef, error)
@@ -24,34 +30,50 @@ type L1Source interface {
 // L1Accessor has the concept of confirmation depth, which is used to block access to requests to blocks which are too recent.
 // When requests for blocks are more recent than the tip minus the confirmation depth, a NotFound error is returned.
 type L1Accessor struct {
-	log      log.Logger
+	log log.Logger
+
 	client   L1Source // may be nil if no source is attached
 	clientMu sync.RWMutex
 
-	finalityHandler eth.HeadSignalFn
-	finalitySub     ethereum.Subscription
+	emitter event.Emitter
+
+	finalitySub ethereum.Subscription
 
 	// tipHeight is the height of the L1 chain tip
 	// used to block access to requests more recent than the confirmation depth
 	tipHeight uint64
 	latestSub ethereum.Subscription
 	confDepth uint64
+
+	// to interrupt requests, so the system can shut down quickly
+	sysCtx context.Context
 }
 
-func NewL1Accessor(log log.Logger, client L1Source, finalityHandler eth.HeadSignalFn) *L1Accessor {
+var _ event.AttachEmitter = (*L1Accessor)(nil)
+
+func NewL1Accessor(sysCtx context.Context, log log.Logger, client L1Source) *L1Accessor {
 	return &L1Accessor{
-		log:             log.New("service", "l1-processor"),
-		client:          client,
-		finalityHandler: finalityHandler,
+		log:    log.New("service", "l1-processor"),
+		client: client,
 		// placeholder confirmation depth
 		confDepth: 2,
+		sysCtx:    sysCtx,
 	}
 }
 
-// AttachClient attaches a new client to the processor
-// if an existing client is attached, the old subscriptions are unsubscribed
-// and new subscriptions are created
-func (p *L1Accessor) AttachClient(client L1Source) {
+func (p *L1Accessor) AttachEmitter(em event.Emitter) {
+	p.emitter = em
+}
+
+func (p *L1Accessor) OnEvent(ev event.Event) bool {
+	return false
+}
+
+// AttachClient attaches a new client to the processor.
+// If an existing client was attached, the old subscriptions are unsubscribed.
+// New subscriptions are created if subscribe is true.
+// If subscribe is false, L1 status has to be fetched manually with PullFinalized and PullLatest.
+func (p *L1Accessor) AttachClient(client L1Source, subscribe bool) {
 	p.clientMu.Lock()
 	defer p.clientMu.Unlock()
 
@@ -67,11 +89,8 @@ func (p *L1Accessor) AttachClient(client L1Source) {
 
 	p.client = client
 
-	// resubscribe to the finality handler
-	p.SubscribeFinalityHandler()
-
-	// if we have a handler function, resubscribe to the finality handler
-	if p.finalityHandler != nil {
+	if client != nil && subscribe {
+		p.SubscribeLatestHandler()
 		p.SubscribeFinalityHandler()
 	}
 }
@@ -80,23 +99,66 @@ func (p *L1Accessor) SubscribeFinalityHandler() {
 	p.finalitySub = eth.PollBlockChanges(
 		p.log,
 		p.client,
-		p.finalityHandler,
+		p.onFinalized,
 		eth.Finalized,
 		3*time.Second,
-		10*time.Second)
+		reqTimeout)
 }
 
 func (p *L1Accessor) SubscribeLatestHandler() {
 	p.latestSub = eth.PollBlockChanges(
 		p.log,
 		p.client,
-		p.SetTipHeight,
+		p.onLatest,
 		eth.Unsafe,
 		3*time.Second,
-		10*time.Second)
+		reqTimeout)
+}
+
+func (p *L1Accessor) SetConfDepth(depth uint64) {
+	p.confDepth = depth
+}
+
+func (p *L1Accessor) PullFinalized() error {
+	p.clientMu.RLock()
+	defer p.clientMu.RUnlock()
+	if p.client == nil {
+		return errors.New("no L1 source configured")
+	}
+
+	ctx, cancel := context.WithTimeout(p.sysCtx, reqTimeout)
+	defer cancel()
+	ref, err := p.client.L1BlockRefByLabel(ctx, eth.Finalized)
+	if err != nil {
+		return fmt.Errorf("failed to pull finalized block ref: %w", err)
+	}
+	p.onFinalized(p.sysCtx, ref)
+	return nil
+}
+
+func (p *L1Accessor) PullLatest() error {
+	p.clientMu.RLock()
+	defer p.clientMu.RUnlock()
+
+	if p.client == nil {
+		return errors.New("no L1 source configured")
+	}
+
+	ctx, cancel := context.WithTimeout(p.sysCtx, reqTimeout)
+	defer cancel()
+	ref, err := p.client.L1BlockRefByLabel(ctx, eth.Unsafe)
+	if err != nil {
+		return fmt.Errorf("failed to pull latest block ref: %w", err)
+	}
+	p.onLatest(p.sysCtx, ref)
+	return nil
+}
+
+func (p *L1Accessor) onFinalized(ctx context.Context, ref eth.L1BlockRef) {
+	p.emitter.Emit(superevents.FinalizedL1RequestEvent{FinalizedL1: ref})
 }
 
-func (p *L1Accessor) SetTipHeight(ctx context.Context, ref eth.L1BlockRef) {
+func (p *L1Accessor) onLatest(ctx context.Context, ref eth.L1BlockRef) {
 	p.tipHeight = ref.Number
 }
 

op-supervisor/supervisor/backend/l1access/l1_accessor_test.go

@@ -40,7 +40,7 @@ func TestL1Accessor(t *testing.T) {
 			Number: number,
 		}, nil
 	}
-	accessor := NewL1Accessor(log, source, nil)
+	accessor := NewL1Accessor(context.Background(), log, source)
 	accessor.tipHeight = 10
 
 	// Test L1BlockRefByNumber
@@ -54,7 +54,7 @@ func TestL1Accessor(t *testing.T) {
 
 	// attach a new source
 	source2 := &mockL1Source{}
-	accessor.AttachClient(source2)
+	accessor.AttachClient(source2, false)
 	require.Equal(t, source2, accessor.client)
 
 }

op-supervisor/supervisor/backend/processors/chain_processor.go

@@ -6,7 +6,6 @@ import (
 	"fmt"
 	"slices"
 	"sync"
-	"sync/atomic"
 	"time"
 
 	"github.com/ethereum/go-ethereum"
@@ -14,7 +13,9 @@ import (
 	gethtypes "github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/log"
 
+	"github.com/ethereum-optimism/optimism/op-node/rollup/event"
 	"github.com/ethereum-optimism/optimism/op-service/eth"
+	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend/superevents"
 	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/types"
 )
 
@@ -48,57 +49,42 @@ type ChainProcessor struct {
 
 	chain types.ChainID
 
+	systemContext context.Context
+
 	processor LogProcessor
 	rewinder  DatabaseRewinder
 
-	// the last known head. May be 0 if not known.
-	lastHead atomic.Uint64
-	// channel with capacity of 1, full if there is work to do
-	newHead chan struct{}
-
-	// to signal to the other services that new indexed data is available
-	onIndexed func()
-
-	// lifetime management of the chain processor
-	ctx    context.Context
-	cancel context.CancelFunc
-	wg     sync.WaitGroup
+	emitter event.Emitter
 
 	maxFetcherThreads int
 }
 
-func NewChainProcessor(log log.Logger, chain types.ChainID, processor LogProcessor, rewinder DatabaseRewinder, onIndexed func()) *ChainProcessor {
-	ctx, cancel := context.WithCancel(context.Background())
+var _ event.AttachEmitter = (*ChainProcessor)(nil)
+var _ event.Deriver = (*ChainProcessor)(nil)
+
+func NewChainProcessor(systemContext context.Context, log log.Logger, chain types.ChainID, processor LogProcessor, rewinder DatabaseRewinder) *ChainProcessor {
 	out := &ChainProcessor{
+		systemContext:     systemContext,
 		log:               log.New("chain", chain),
 		client:            nil,
 		chain:             chain,
 		processor:         processor,
 		rewinder:          rewinder,
-		newHead:           make(chan struct{}, 1),
-		onIndexed:         onIndexed,
-		ctx:               ctx,
-		cancel:            cancel,
 		maxFetcherThreads: 10,
 	}
 	return out
 }
 
+func (s *ChainProcessor) AttachEmitter(em event.Emitter) {
+	s.emitter = em
+}
+
 func (s *ChainProcessor) SetSource(cl Source) {
 	s.clientLock.Lock()
 	defer s.clientLock.Unlock()
 	s.client = cl
 }
 
-func (s *ChainProcessor) StartBackground() {
-	s.wg.Add(1)
-	go s.worker()
-}
-
-func (s *ChainProcessor) ProcessToHead() {
-	s.work()
-}
-
 func (s *ChainProcessor) nextNum() uint64 {
 	headNum, ok := s.rewinder.LatestBlockNum(s.chain)
 	if !ok {
@@ -107,55 +93,41 @@ func (s *ChainProcessor) nextNum() uint64 {
 	return headNum + 1
 }
 
-// worker is the main loop of the chain processor's worker
-// it manages work by request or on a timer, and watches for shutdown
-func (s *ChainProcessor) worker() {
-	defer s.wg.Done()
-
-	delay := time.NewTicker(time.Second * 5)
-	for {
-		// await next time we process, or detect shutdown
-		select {
-		case <-s.ctx.Done():
-			delay.Stop()
-			return
-		case <-s.newHead:
-			s.log.Debug("Responding to new head signal")
-			s.work()
-		case <-delay.C:
-			s.log.Debug("Checking for updates")
-			s.work()
+func (s *ChainProcessor) OnEvent(ev event.Event) bool {
+	switch x := ev.(type) {
+	case superevents.ChainProcessEvent:
+		if x.ChainID != s.chain {
+			return false
 		}
+		s.onRequest(x.Target)
+	default:
+		return false
 	}
+	return true
 }
 
-// work processes the next block in the chain repeatedly until it reaches the head
-func (s *ChainProcessor) work() {
-	for {
-		if s.ctx.Err() != nil { // check if we are closing down
-			return
-		}
-		_, err := s.rangeUpdate()
-		target := s.nextNum()
-		if err != nil {
-			if errors.Is(err, ethereum.NotFound) {
-				s.log.Debug("Event-indexer cannot find next block yet", "target", target, "err", err)
-			} else if errors.Is(err, types.ErrNoRPCSource) {
-				s.log.Warn("No RPC source configured, cannot process new blocks")
-			} else {
-				s.log.Error("Failed to process new block", "err", err)
-			}
-		} else if x := s.lastHead.Load(); target+1 <= x {
-			s.log.Debug("Continuing with next block", "newTarget", target+1, "lastHead", x)
-			continue // instantly continue processing, no need to idle
+func (s *ChainProcessor) onRequest(target uint64) {
+	_, err := s.rangeUpdate(target)
+	if err != nil {
+		if errors.Is(err, ethereum.NotFound) {
+			s.log.Debug("Event-indexer cannot find next block yet", "target", target, "err", err)
+		} else if errors.Is(err, types.ErrNoRPCSource) {
+			s.log.Warn("No RPC source configured, cannot process new blocks")
 		} else {
-			s.log.Debug("Idling block-processing, reached latest block", "head", target)
+			s.log.Error("Failed to process new block", "err", err)
 		}
-		return
+	} else if x := s.nextNum(); x <= target {
+		s.log.Debug("Continuing with next block", "target", target, "next", x)
+		s.emitter.Emit(superevents.ChainProcessEvent{
+			ChainID: s.chain,
+			Target:  target,
+		}) // instantly continue processing, no need to idle
+	} else {
+		s.log.Debug("Idling block-processing, reached latest block", "head", target)
 	}
 }
 
-func (s *ChainProcessor) rangeUpdate() (int, error) {
+func (s *ChainProcessor) rangeUpdate(target uint64) (int, error) {
 	s.clientLock.Lock()
 	defer s.clientLock.Unlock()
 	if s.client == nil {
@@ -165,7 +137,7 @@ func (s *ChainProcessor) rangeUpdate() (int, error) {
 	// define the range of blocks to fetch
 	// [next, last] inclusive with a max of s.fetcherThreads blocks
 	next := s.nextNum()
-	last := s.lastHead.Load()
+	last := target
 
 	nums := make([]uint64, 0, s.maxFetcherThreads)
 	for i := next; i <= last; i++ {
@@ -201,7 +173,7 @@ func (s *ChainProcessor) rangeUpdate() (int, error) {
 		defer func() { parallelResults <- result }()
 
 		// fetch the block ref
-		ctx, cancel := context.WithTimeout(s.ctx, time.Second*10)
+		ctx, cancel := context.WithTimeout(s.systemContext, time.Second*10)
 		nextL1, err := s.client.BlockRefByNumber(ctx, num)
 		cancel()
 		if err != nil {
@@ -217,7 +189,7 @@ func (s *ChainProcessor) rangeUpdate() (int, error) {
 		result.blockRef = &next
 
 		// fetch receipts
-		ctx, cancel = context.WithTimeout(s.ctx, time.Second*10)
+		ctx, cancel = context.WithTimeout(s.systemContext, time.Second*10)
 		receipts, err := s.client.FetchReceipts(ctx, next.Hash)
 		cancel()
 		if err != nil {
@@ -258,7 +230,7 @@ func (s *ChainProcessor) rangeUpdate() (int, error) {
 			return i, fmt.Errorf("failed to fetch block %d: %w", results[i].num, results[i].err)
 		}
 		// process the receipts
-		err := s.process(s.ctx, *results[i].blockRef, results[i].receipts)
+		err := s.process(s.systemContext, *results[i].blockRef, results[i].receipts)
 		if err != nil {
 			return i, fmt.Errorf("failed to process block %d: %w", results[i].num, err)
 		}
@@ -283,24 +255,5 @@ func (s *ChainProcessor) process(ctx context.Context, next eth.BlockRef, receipt
 		return err
 	}
 	s.log.Info("Indexed block events", "block", next, "txs", len(receipts))
-	s.onIndexed()
 	return nil
-
-}
-
-func (s *ChainProcessor) OnNewHead(head eth.BlockRef) error {
-	// update the latest target
-	s.lastHead.Store(head.Number)
-	// signal that we have something to process
-	select {
-	case s.newHead <- struct{}{}:
-	default:
-		// already requested an update
-	}
-	return nil
-}
-
-func (s *ChainProcessor) Close() {
-	s.cancel()
-	s.wg.Wait()
 }

op-supervisor/supervisor/backend/processors/l1_finality_processor.go

-package processors
-
-import (
-	"context"
-
-	"github.com/ethereum-optimism/optimism/op-service/eth"
-	"github.com/ethereum/go-ethereum/log"
-)
-
-type chainsDB interface {
-	FinalizedL1() eth.BlockRef
-	UpdateFinalizedL1(finalized eth.BlockRef) error
-}
-
-// MaybeUpdateFinalizedL1Fn returns a HeadSignalFn that updates the database with the new finalized block if it is newer than the current one.
-func MaybeUpdateFinalizedL1Fn(ctx context.Context, logger log.Logger, db chainsDB) eth.HeadSignalFn {
-	return func(ctx context.Context, ref eth.L1BlockRef) {
-		// do something with the new block
-		logger.Debug("Received new Finalized L1 block", "block", ref)
-		currentFinalized := db.FinalizedL1()
-		if currentFinalized.Number > ref.Number {
-			logger.Warn("Finalized block in database is newer than subscribed finalized block", "current", currentFinalized, "new", ref)
-			return
-		}
-		if ref.Number > currentFinalized.Number || currentFinalized == (eth.BlockRef{}) {
-			// update the database with the new finalized block
-			if err := db.UpdateFinalizedL1(ref); err != nil {
-				logger.Warn("Failed to update finalized L1", "err", err)
-				return
-			}
-			logger.Debug("Updated finalized L1 block", "block", ref)
-		}
-	}
-}

op-supervisor/supervisor/backend/processors/log_processor.go

@@ -18,11 +18,6 @@ type LogStorage interface {
 	AddLog(chain types.ChainID, logHash common.Hash, parentBlock eth.BlockID, logIdx uint32, execMsg *types.ExecutingMessage) error
 }
 
-type ChainsDBClientForLogProcessor interface {
-	SealBlock(chain types.ChainID, block eth.BlockRef) error
-	AddLog(chain types.ChainID, logHash common.Hash, parentBlock eth.BlockID, logIdx uint32, execMsg *types.ExecutingMessage) error
-}
-
 type logProcessor struct {
 	chain        types.ChainID
 	logStore     LogStorage

op-supervisor/supervisor/backend/superevents/events.go

+package superevents
+
+import (
+	"github.com/ethereum-optimism/optimism/op-service/eth"
+	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/types"
+)
+
+type ChainProcessEvent struct {
+	ChainID types.ChainID
+	Target  uint64
+}
+
+func (ev ChainProcessEvent) String() string {
+	return "chain-process"
+}
+
+type UpdateCrossUnsafeRequestEvent struct {
+	ChainID types.ChainID
+}
+
+func (ev UpdateCrossUnsafeRequestEvent) String() string {
+	return "update-cross-unsafe-request"
+}
+
+type UpdateCrossSafeRequestEvent struct {
+	ChainID types.ChainID
+}
+
+func (ev UpdateCrossSafeRequestEvent) String() string {
+	return "update-cross-safe-request"
+}
+
+type LocalUnsafeUpdateEvent struct {
+	ChainID        types.ChainID
+	NewLocalUnsafe eth.BlockRef
+}
+
+func (ev LocalUnsafeUpdateEvent) String() string {
+	return "local-unsafe-update"
+}
+
+type LocalSafeUpdateEvent struct {
+	ChainID      types.ChainID
+	NewLocalSafe types.DerivedBlockSealPair
+}
+
+func (ev LocalSafeUpdateEvent) String() string {
+	return "local-safe-update"
+}
+
+type CrossUnsafeUpdateEvent struct {
+	ChainID        types.ChainID
+	NewCrossUnsafe types.BlockSeal
+}
+
+func (ev CrossUnsafeUpdateEvent) String() string {
+	return "cross-unsafe-update"
+}
+
+type CrossSafeUpdateEvent struct {
+	ChainID      types.ChainID
+	NewCrossSafe types.DerivedBlockSealPair
+}
+
+func (ev CrossSafeUpdateEvent) String() string {
+	return "cross-safe-update"
+}
+
+type FinalizedL1RequestEvent struct {
+	FinalizedL1 eth.BlockRef
+}
+
+func (ev FinalizedL1RequestEvent) String() string {
+	return "finalized-l1-request"
+}
+
+type FinalizedL1UpdateEvent struct {
+	FinalizedL1 eth.BlockRef
+}
+
+func (ev FinalizedL1UpdateEvent) String() string {
+	return "finalized-l1-update"
+}
+
+type FinalizedL2UpdateEvent struct {
+	ChainID     types.ChainID
+	FinalizedL2 types.BlockSeal
+}
+
+func (ev FinalizedL2UpdateEvent) String() string {
+	return "finalized-l2-update"
+}
+
+type LocalSafeOutOfSyncEvent struct {
+	ChainID types.ChainID
+	L1Ref   eth.BlockRef
+	Err     error
+}
+
+func (ev LocalSafeOutOfSyncEvent) String() string {
+	return "local-safe-out-of-sync"
+}
+
+type LocalUnsafeReceivedEvent struct {
+	ChainID        types.ChainID
+	NewLocalUnsafe eth.BlockRef
+}
+
+func (ev LocalUnsafeReceivedEvent) String() string {
+	return "local-unsafe-received"
+}
+
+type LocalDerivedEvent struct {
+	ChainID types.ChainID
+	Derived types.DerivedBlockRefPair
+}
+
+func (ev LocalDerivedEvent) String() string {
+	return "local-derived"
+}
+
+type AnchorEvent struct {
+	ChainID types.ChainID
+	Anchor  types.DerivedBlockRefPair
+}
+
+func (ev AnchorEvent) String() string {
+	return "anchor"
+}

op-supervisor/supervisor/backend/syncnode/controller.go

@@ -2,13 +2,15 @@ package syncnode
 
 import (
 	"context"
-	"errors"
 	"fmt"
+	"sync/atomic"
 
 	"github.com/ethereum/go-ethereum/log"
 
+	"github.com/ethereum-optimism/optimism/op-node/rollup/event"
 	"github.com/ethereum-optimism/optimism/op-service/locks"
 	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend/depset"
+	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend/superevents"
 	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/types"
 )
 
@@ -18,24 +20,38 @@ import (
 type SyncNodesController struct {
 	logger log.Logger
 
+	id          atomic.Uint64
 	controllers locks.RWMap[types.ChainID, *locks.RWMap[*ManagedNode, struct{}]]
 
+	eventSys event.System
+
+	emitter event.Emitter
+
 	backend backend
-	db      chainsDB
 
 	depSet depset.DependencySet
 }
 
+var _ event.AttachEmitter = (*SyncNodesController)(nil)
+
 // NewSyncNodesController creates a new SyncNodeController
-func NewSyncNodesController(l log.Logger, depset depset.DependencySet, db chainsDB, backend backend) *SyncNodesController {
+func NewSyncNodesController(l log.Logger, depset depset.DependencySet, eventSys event.System, backend backend) *SyncNodesController {
 	return &SyncNodesController{
-		logger:  l,
-		depSet:  depset,
-		db:      db,
-		backend: backend,
+		logger:   l,
+		depSet:   depset,
+		eventSys: eventSys,
+		backend:  backend,
 	}
 }
 
+func (snc *SyncNodesController) AttachEmitter(em event.Emitter) {
+	snc.emitter = em
+}
+
+func (snc *SyncNodesController) OnEvent(ev event.Event) bool {
+	return false
+}
+
 func (snc *SyncNodesController) Close() error {
 	snc.controllers.Range(func(chainID types.ChainID, controllers *locks.RWMap[*ManagedNode, struct{}]) bool {
 		controllers.Range(func(node *ManagedNode, _ struct{}) bool {
@@ -49,59 +65,30 @@ func (snc *SyncNodesController) Close() error {
 
 // AttachNodeController attaches a node to be managed by the supervisor.
 // If noSubscribe, the node is not actively polled/subscribed to, and requires manual ManagedNode.PullEvents calls.
-func (snc *SyncNodesController) AttachNodeController(id types.ChainID, ctrl SyncControl, noSubscribe bool) (Node, error) {
-	if !snc.depSet.HasChain(id) {
-		return nil, fmt.Errorf("chain %v not in dependency set: %w", id, types.ErrUnknownChain)
+func (snc *SyncNodesController) AttachNodeController(chainID types.ChainID, ctrl SyncControl, noSubscribe bool) (Node, error) {
+	if !snc.depSet.HasChain(chainID) {
+		return nil, fmt.Errorf("chain %v not in dependency set: %w", chainID, types.ErrUnknownChain)
 	}
 	// lazy init the controllers map for this chain
-	if !snc.controllers.Has(id) {
-		snc.controllers.Set(id, &locks.RWMap[*ManagedNode, struct{}]{})
-	}
-	controllersForChain, _ := snc.controllers.Get(id)
-	node := NewManagedNode(snc.logger, id, ctrl, snc.db, snc.backend, noSubscribe)
+	snc.controllers.Default(chainID, func() *locks.RWMap[*ManagedNode, struct{}] {
+		return &locks.RWMap[*ManagedNode, struct{}]{}
+	})
+	controllersForChain, _ := snc.controllers.Get(chainID)
+	node := NewManagedNode(snc.logger, chainID, ctrl, snc.backend, noSubscribe)
+
+	nodeID := snc.id.Add(1)
+	name := fmt.Sprintf("syncnode-%s-%d", chainID, nodeID)
+	snc.eventSys.Register(name, node, event.DefaultRegisterOpts())
+
 	controllersForChain.Set(node, struct{}{})
 	anchor, err := ctrl.AnchorPoint(context.Background())
 	if err != nil {
 		return nil, fmt.Errorf("failed to get anchor point: %w", err)
 	}
-	snc.maybeInitSafeDB(id, anchor)
-	snc.maybeInitEventsDB(id, anchor)
+	snc.emitter.Emit(superevents.AnchorEvent{
+		ChainID: chainID,
+		Anchor:  anchor,
+	})
 	node.Start()
 	return node, nil
 }
-
-// maybeInitSafeDB initializes the chain database if it is not already initialized
-// it checks if the Local Safe database is empty, and loads it with the Anchor Point if so
-func (snc *SyncNodesController) maybeInitSafeDB(id types.ChainID, anchor types.DerivedBlockRefPair) {
-	_, err := snc.db.LocalSafe(id)
-	if errors.Is(err, types.ErrFuture) {
-		snc.logger.Debug("initializing chain database", "chain", id)
-		if err := snc.db.UpdateCrossSafe(id, anchor.DerivedFrom, anchor.Derived); err != nil {
-			snc.logger.Warn("failed to initialize cross safe", "chain", id, "error", err)
-		}
-		if err := snc.db.UpdateLocalSafe(id, anchor.DerivedFrom, anchor.Derived); err != nil {
-			snc.logger.Warn("failed to initialize local safe", "chain", id, "error", err)
-		}
-		snc.logger.Debug("initialized chain database", "chain", id, "anchor", anchor)
-	} else if err != nil {
-		snc.logger.Warn("failed to check if chain database is initialized", "chain", id, "error", err)
-	} else {
-		snc.logger.Debug("chain database already initialized", "chain", id)
-	}
-}
-
-func (snc *SyncNodesController) maybeInitEventsDB(id types.ChainID, anchor types.DerivedBlockRefPair) {
-	_, _, _, err := snc.db.OpenBlock(id, 0)
-	if errors.Is(err, types.ErrFuture) {
-		snc.logger.Debug("initializing events database", "chain", id)
-		err := snc.backend.UpdateLocalUnsafe(context.Background(), id, anchor.Derived)
-		if err != nil {
-			snc.logger.Warn("failed to seal initial block", "chain", id, "error", err)
-		}
-		snc.logger.Debug("initialized events database", "chain", id)
-	} else if err != nil {
-		snc.logger.Warn("failed to check if logDB is initialized", "chain", id, "error", err)
-	} else {
-		snc.logger.Debug("events database already initialized", "chain", id)
-	}
-}

op-supervisor/supervisor/backend/syncnode/controller_test.go

@@ -4,69 +4,20 @@ import (
 	"context"
 	"testing"
 
+	"github.com/stretchr/testify/require"
+
+	"github.com/ethereum/go-ethereum"
+	gethevent "github.com/ethereum/go-ethereum/event"
+	"github.com/ethereum/go-ethereum/log"
+
+	"github.com/ethereum-optimism/optimism/op-node/rollup/event"
 	"github.com/ethereum-optimism/optimism/op-service/eth"
 	"github.com/ethereum-optimism/optimism/op-service/testlog"
 	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend/depset"
+	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend/superevents"
 	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/types"
-	"github.com/ethereum/go-ethereum"
-	gethevent "github.com/ethereum/go-ethereum/event"
-	"github.com/ethereum/go-ethereum/log"
-	"github.com/stretchr/testify/require"
 )
 
-type mockChainsDB struct {
-	localSafeFn       func(chainID types.ChainID) (types.DerivedBlockSealPair, error)
-	updateLocalSafeFn func(chainID types.ChainID, ref eth.BlockRef, derived eth.BlockRef) error
-	updateCrossSafeFn func(chainID types.ChainID, ref eth.BlockRef, derived eth.BlockRef) error
-	openBlockFn       func(chainID types.ChainID, i uint64) (seal eth.BlockRef, logCount uint32, execMsgs map[uint32]*types.ExecutingMessage, err error)
-
-	subscribeCrossUnsafe gethevent.FeedOf[types.BlockSeal]
-	subscribeCrosSafe    gethevent.FeedOf[types.DerivedBlockSealPair]
-	subscribeFinalized   gethevent.FeedOf[types.BlockSeal]
-}
-
-func (m *mockChainsDB) OpenBlock(chainID types.ChainID, i uint64) (seal eth.BlockRef, logCount uint32, execMsgs map[uint32]*types.ExecutingMessage, err error) {
-	if m.openBlockFn != nil {
-		return m.openBlockFn(chainID, i)
-	}
-	return eth.BlockRef{}, 0, nil, nil
-}
-
-func (m *mockChainsDB) UpdateLocalSafe(chainID types.ChainID, ref eth.BlockRef, derived eth.BlockRef) error {
-	if m.updateLocalSafeFn != nil {
-		return m.updateLocalSafeFn(chainID, ref, derived)
-	}
-	return nil
-}
-
-func (m *mockChainsDB) LocalSafe(chainID types.ChainID) (types.DerivedBlockSealPair, error) {
-	if m.localSafeFn != nil {
-		return m.localSafeFn(chainID)
-	}
-	return types.DerivedBlockSealPair{}, nil
-}
-
-func (m *mockChainsDB) UpdateCrossSafe(chainID types.ChainID, ref eth.BlockRef, derived eth.BlockRef) error {
-	if m.updateCrossSafeFn != nil {
-		return m.updateCrossSafeFn(chainID, ref, derived)
-	}
-	return nil
-}
-
-func (m *mockChainsDB) SubscribeCrossUnsafe(chainID types.ChainID, c chan<- types.BlockSeal) (gethevent.Subscription, error) {
-	return m.subscribeCrossUnsafe.Subscribe(c), nil
-}
-
-func (m *mockChainsDB) SubscribeCrossSafe(chainID types.ChainID, c chan<- types.DerivedBlockSealPair) (gethevent.Subscription, error) {
-	return m.subscribeCrosSafe.Subscribe(c), nil
-}
-
-func (m *mockChainsDB) SubscribeFinalized(chainID types.ChainID, c chan<- types.BlockSeal) (gethevent.Subscription, error) {
-	return m.subscribeFinalized.Subscribe(c), nil
-}
-
-var _ chainsDB = (*mockChainsDB)(nil)
-
 type mockSyncControl struct {
 	anchorPointFn       func(ctx context.Context) (types.DerivedBlockRefPair, error)
 	provideL1Fn         func(ctx context.Context, ref eth.BlockRef) error
@@ -134,11 +85,7 @@ func (m *mockSyncControl) UpdateFinalized(ctx context.Context, id eth.BlockID) e
 
 var _ SyncControl = (*mockSyncControl)(nil)
 
-type mockBackend struct {
-	updateLocalUnsafeFn func(ctx context.Context, chainID types.ChainID, head eth.BlockRef) error
-	updateLocalSafeFn   func(ctx context.Context, chainID types.ChainID, derivedFrom eth.BlockRef, lastDerived eth.BlockRef) error
-	recordL1Fn          func(ctx context.Context, chain types.ChainID, ref eth.BlockRef) error
-}
+type mockBackend struct{}
 
 func (m *mockBackend) LocalSafe(ctx context.Context, chainID types.ChainID) (pair types.DerivedIDPair, err error) {
 	return types.DerivedIDPair{}, nil
@@ -148,10 +95,6 @@ func (m *mockBackend) LocalUnsafe(ctx context.Context, chainID types.ChainID) (e
 	return eth.BlockID{}, nil
 }
 
-func (m *mockBackend) LatestUnsafe(ctx context.Context, chainID types.ChainID) (eth.BlockID, error) {
-	return eth.BlockID{}, nil
-}
-
 func (m *mockBackend) SafeDerivedAt(ctx context.Context, chainID types.ChainID, derivedFrom eth.BlockID) (derived eth.BlockID, err error) {
 	return eth.BlockID{}, nil
 }
@@ -160,31 +103,10 @@ func (m *mockBackend) Finalized(ctx context.Context, chainID types.ChainID) (eth
 	return eth.BlockID{}, nil
 }
 
-func (m *mockBackend) UpdateLocalSafe(ctx context.Context, chainID types.ChainID, derivedFrom eth.BlockRef, lastDerived eth.BlockRef) error {
-	if m.updateLocalSafeFn != nil {
-		return m.updateLocalSafeFn(ctx, chainID, derivedFrom, lastDerived)
-	}
-	return nil
-}
-
-func (m *mockBackend) UpdateLocalUnsafe(ctx context.Context, chainID types.ChainID, head eth.BlockRef) error {
-	if m.updateLocalUnsafeFn != nil {
-		return m.updateLocalUnsafeFn(ctx, chainID, head)
-	}
-	return nil
-}
-
 func (m *mockBackend) L1BlockRefByNumber(ctx context.Context, number uint64) (eth.L1BlockRef, error) {
 	return eth.L1BlockRef{}, nil
 }
 
-func (m *mockBackend) RecordNewL1(ctx context.Context, chain types.ChainID, ref eth.BlockRef) error {
-	if m.recordL1Fn != nil {
-		return m.recordL1Fn(ctx, chain, ref)
-	}
-	return nil
-}
-
 var _ backend = (*mockBackend)(nil)
 
 func sampleDepSet(t *testing.T) depset.DependencySet {
@@ -205,11 +127,38 @@ func sampleDepSet(t *testing.T) depset.DependencySet {
 	return depSet
 }
 
+type eventMonitor struct {
+	anchorCalled        int
+	localDerived        int
+	receivedLocalUnsafe int
+}
+
+func (m *eventMonitor) OnEvent(ev event.Event) bool {
+	switch ev.(type) {
+	case superevents.AnchorEvent:
+		m.anchorCalled += 1
+	case superevents.LocalDerivedEvent:
+		m.localDerived += 1
+	case superevents.LocalUnsafeReceivedEvent:
+		m.receivedLocalUnsafe += 1
+	default:
+		return false
+	}
+	return true
+}
+
 // TestInitFromAnchorPoint tests that the SyncNodesController uses the Anchor Point to initialize databases
 func TestInitFromAnchorPoint(t *testing.T) {
 	logger := testlog.Logger(t, log.LvlInfo)
 	depSet := sampleDepSet(t)
-	controller := NewSyncNodesController(logger, depSet, &mockChainsDB{}, &mockBackend{})
+	ex := event.NewGlobalSynchronous(context.Background())
+	eventSys := event.NewSystem(logger, ex)
+
+	mon := &eventMonitor{}
+	eventSys.Register("monitor", mon, event.DefaultRegisterOpts())
+
+	controller := NewSyncNodesController(logger, depSet, eventSys, &mockBackend{})
+	eventSys.Register("controller", controller, event.DefaultRegisterOpts())
 
 	require.Zero(t, controller.controllers.Len(), "controllers should be empty to start")
 
@@ -223,53 +172,18 @@ func TestInitFromAnchorPoint(t *testing.T) {
 		}, nil
 	}
 
-	// have the local safe return an error to trigger the initialization
-	controller.db.(*mockChainsDB).localSafeFn = func(chainID types.ChainID) (types.DerivedBlockSealPair, error) {
-		return types.DerivedBlockSealPair{}, types.ErrFuture
-	}
-	// record when the updateLocalSafe function is called
-	localCalled := 0
-	controller.db.(*mockChainsDB).updateLocalSafeFn = func(chainID types.ChainID, ref eth.BlockRef, derived eth.BlockRef) error {
-		localCalled++
-		return nil
-	}
-	// record when the updateCrossSafe function is called
-	crossCalled := 0
-	controller.db.(*mockChainsDB).updateCrossSafeFn = func(chainID types.ChainID, ref eth.BlockRef, derived eth.BlockRef) error {
-		crossCalled++
-		return nil
-	}
-
-	// have OpenBlock return an error to trigger the initialization
-	controller.db.(*mockChainsDB).openBlockFn = func(chainID types.ChainID, i uint64) (seal eth.BlockRef, logCount uint32, execMsgs map[uint32]*types.ExecutingMessage, err error) {
-		return eth.BlockRef{}, 0, nil, types.ErrFuture
-	}
-	unsafeCalled := 0
-	controller.backend.(*mockBackend).updateLocalUnsafeFn = func(ctx context.Context, chainID types.ChainID, head eth.BlockRef) error {
-		unsafeCalled++
-		return nil
-	}
-
 	// after the first attach, both databases are called for update
 	_, err := controller.AttachNodeController(types.ChainIDFromUInt64(900), &ctrl, false)
-
 	require.NoError(t, err)
-	require.Equal(t, 1, localCalled, "local safe should have been updated once")
-	require.Equal(t, 1, crossCalled, "cross safe should have been updated twice")
-	require.Equal(t, 1, unsafeCalled, "local unsafe should have been updated once")
+	require.NoError(t, ex.Drain())
+	require.Equal(t, 1, mon.anchorCalled, "an anchor point should be received")
 
-	// reset the local safe function to return no error
-	controller.db.(*mockChainsDB).localSafeFn = nil
-	// reset the open block function to return no error
-	controller.db.(*mockChainsDB).openBlockFn = nil
-
-	// after the second attach, there are no additional updates (no empty signal from the DB)
+	// on second attach we send the anchor again; it's up to the DB to use it or not.
 	ctrl2 := mockSyncControl{}
 	_, err = controller.AttachNodeController(types.ChainIDFromUInt64(901), &ctrl2, false)
 	require.NoError(t, err)
-	require.Equal(t, 1, localCalled, "local safe should have been updated once")
-	require.Equal(t, 1, crossCalled, "cross safe should have been updated once")
-	require.Equal(t, 1, unsafeCalled, "local unsafe should have been updated once")
+	require.NoError(t, ex.Drain())
+	require.Equal(t, 2, mon.anchorCalled, "anchor point again")
 }
 
 // TestAttachNodeController tests the AttachNodeController function of the SyncNodesController.
@@ -277,8 +191,10 @@ func TestInitFromAnchorPoint(t *testing.T) {
 func TestAttachNodeController(t *testing.T) {
 	logger := log.New()
 	depSet := sampleDepSet(t)
-	controller := NewSyncNodesController(logger, depSet, &mockChainsDB{}, &mockBackend{})
-
+	ex := event.NewGlobalSynchronous(context.Background())
+	eventSys := event.NewSystem(logger, ex)
+	controller := NewSyncNodesController(logger, depSet, eventSys, &mockBackend{})
+	eventSys.Register("controller", controller, event.DefaultRegisterOpts())
 	require.Zero(t, controller.controllers.Len(), "controllers should be empty to start")
 
 	// Attach a controller for chain 900

op-supervisor/supervisor/backend/syncnode/iface.go

@@ -51,8 +51,4 @@ type SyncNode interface {
 
 type Node interface {
 	PullEvents(ctx context.Context) (pulledAny bool, err error)
-
-	AwaitSentCrossUnsafeUpdate(ctx context.Context, minNum uint64) error
-	AwaitSentCrossSafeUpdate(ctx context.Context, minNum uint64) error
-	AwaitSentFinalizedUpdate(ctx context.Context, minNum uint64) error
 }

op-supervisor/supervisor/backend/syncnode/node.go

@@ -14,31 +14,19 @@ import (
 	"github.com/ethereum/go-ethereum"
 	"github.com/ethereum/go-ethereum/log"
 
+	"github.com/ethereum-optimism/optimism/op-node/rollup/event"
 	"github.com/ethereum-optimism/optimism/op-service/eth"
-	"github.com/ethereum-optimism/optimism/op-service/locks"
+	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend/superevents"
 	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/types"
 	gethevent "github.com/ethereum/go-ethereum/event"
 )
 
-type chainsDB interface {
-	LocalSafe(chainID types.ChainID) (types.DerivedBlockSealPair, error)
-	OpenBlock(chainID types.ChainID, blockNum uint64) (seal eth.BlockRef, logCount uint32, execMsgs map[uint32]*types.ExecutingMessage, err error)
-	UpdateLocalSafe(chainID types.ChainID, derivedFrom eth.BlockRef, lastDerived eth.BlockRef) error
-	UpdateCrossSafe(chainID types.ChainID, l1View eth.BlockRef, lastCrossDerived eth.BlockRef) error
-	SubscribeCrossUnsafe(chainID types.ChainID, c chan<- types.BlockSeal) (gethevent.Subscription, error)
-	SubscribeCrossSafe(chainID types.ChainID, c chan<- types.DerivedBlockSealPair) (gethevent.Subscription, error)
-	SubscribeFinalized(chainID types.ChainID, c chan<- types.BlockSeal) (gethevent.Subscription, error)
-}
-
 type backend interface {
-	UpdateLocalSafe(ctx context.Context, chainID types.ChainID, derivedFrom eth.BlockRef, lastDerived eth.BlockRef) error
-	UpdateLocalUnsafe(ctx context.Context, chainID types.ChainID, head eth.BlockRef) error
 	LocalSafe(ctx context.Context, chainID types.ChainID) (pair types.DerivedIDPair, err error)
 	LocalUnsafe(ctx context.Context, chainID types.ChainID) (eth.BlockID, error)
 	SafeDerivedAt(ctx context.Context, chainID types.ChainID, derivedFrom eth.BlockID) (derived eth.BlockID, err error)
 	Finalized(ctx context.Context, chainID types.ChainID) (eth.BlockID, error)
 	L1BlockRefByNumber(ctx context.Context, number uint64) (eth.L1BlockRef, error)
-	RecordNewL1(ctx context.Context, chainID types.ChainID, l1 eth.BlockRef) error
 }
 
 const (
@@ -53,28 +41,23 @@ type ManagedNode struct {
 
 	backend backend
 
-	lastSentCrossUnsafe locks.Watch[eth.BlockID]
-	lastSentCrossSafe   locks.Watch[types.DerivedIDPair]
-	lastSentFinalized   locks.Watch[eth.BlockID]
-
-	// when the supervisor has a cross-safe update for the node
-	crossSafeUpdateChan chan types.DerivedBlockSealPair
-	// when the supervisor has a cross-unsafe update for the node
-	crossUnsafeUpdateChan chan types.BlockSeal
-	// when the supervisor has a finality update for the node
-	finalizedUpdateChan chan types.BlockSeal
-
-	// when the node has an update for us
+	// When the node has an update for us
+	// Nil when node events are pulled synchronously.
 	nodeEvents chan *types.ManagedEvent
 
 	subscriptions []gethevent.Subscription
 
+	emitter event.Emitter
+
 	ctx    context.Context
 	cancel context.CancelFunc
 	wg     sync.WaitGroup
 }
 
-func NewManagedNode(log log.Logger, id types.ChainID, node SyncControl, db chainsDB, backend backend, noSubscribe bool) *ManagedNode {
+var _ event.AttachEmitter = (*ManagedNode)(nil)
+var _ event.Deriver = (*ManagedNode)(nil)
+
+func NewManagedNode(log log.Logger, id types.ChainID, node SyncControl, backend backend, noSubscribe bool) *ManagedNode {
 	ctx, cancel := context.WithCancel(context.Background())
 	m := &ManagedNode{
 		log:     log.New("chain", id),
@@ -84,7 +67,6 @@ func NewManagedNode(log log.Logger, id types.ChainID, node SyncControl, db chain
 		ctx:     ctx,
 		cancel:  cancel,
 	}
-	m.SubscribeToDBEvents(db)
 	if !noSubscribe {
 		m.SubscribeToNodeEvents()
 	}
@@ -92,25 +74,37 @@ func NewManagedNode(log log.Logger, id types.ChainID, node SyncControl, db chain
 	return m
 }
 
-func (m *ManagedNode) SubscribeToDBEvents(db chainsDB) {
-	m.crossUnsafeUpdateChan = make(chan types.BlockSeal, 10)
-	m.crossSafeUpdateChan = make(chan types.DerivedBlockSealPair, 10)
-	m.finalizedUpdateChan = make(chan types.BlockSeal, 10)
-	if sub, err := db.SubscribeCrossUnsafe(m.chainID, m.crossUnsafeUpdateChan); err != nil {
-		m.log.Warn("failed to subscribe to cross unsafe", "err", err)
-	} else {
-		m.subscriptions = append(m.subscriptions, sub)
-	}
-	if sub, err := db.SubscribeCrossSafe(m.chainID, m.crossSafeUpdateChan); err != nil {
-		m.log.Warn("failed to subscribe to cross safe", "err", err)
-	} else {
-		m.subscriptions = append(m.subscriptions, sub)
-	}
-	if sub, err := db.SubscribeFinalized(m.chainID, m.finalizedUpdateChan); err != nil {
-		m.log.Warn("failed to subscribe to finalized", "err", err)
-	} else {
-		m.subscriptions = append(m.subscriptions, sub)
+func (m *ManagedNode) AttachEmitter(em event.Emitter) {
+	m.emitter = em
+}
+
+func (m *ManagedNode) OnEvent(ev event.Event) bool {
+	switch x := ev.(type) {
+	case superevents.CrossUnsafeUpdateEvent:
+		if x.ChainID != m.chainID {
+			return false
+		}
+		m.onCrossUnsafeUpdate(x.NewCrossUnsafe)
+	case superevents.CrossSafeUpdateEvent:
+		if x.ChainID != m.chainID {
+			return false
+		}
+		m.onCrossSafeUpdate(x.NewCrossSafe)
+	case superevents.FinalizedL2UpdateEvent:
+		if x.ChainID != m.chainID {
+			return false
+		}
+		m.onFinalizedL2(x.FinalizedL2)
+	case superevents.LocalSafeOutOfSyncEvent:
+		if x.ChainID != m.chainID {
+			return false
+		}
+		m.resetSignal(x.Err, x.L1Ref)
+	// TODO: watch for reorg events from DB. Send a reset signal to op-node if needed
+	default:
+		return false
 	}
+	return true
 }
 
 func (m *ManagedNode) SubscribeToNodeEvents() {
@@ -159,13 +153,7 @@ func (m *ManagedNode) Start() {
 			case <-m.ctx.Done():
 				m.log.Info("Exiting node syncing")
 				return
-			case seal := <-m.crossUnsafeUpdateChan:
-				m.onCrossUnsafeUpdate(seal)
-			case pair := <-m.crossSafeUpdateChan:
-				m.onCrossSafeUpdate(pair)
-			case seal := <-m.finalizedUpdateChan:
-				m.onFinalizedL2(seal)
-			case ev := <-m.nodeEvents:
+			case ev := <-m.nodeEvents: // nil, indefinitely blocking, if no node-events subscriber is set up.
 				m.onNodeEvent(ev)
 			}
 		}
@@ -229,7 +217,6 @@ func (m *ManagedNode) onCrossUnsafeUpdate(seal types.BlockSeal) {
 		m.log.Warn("Node failed cross-unsafe updating", "err", err)
 		return
 	}
-	m.lastSentCrossUnsafe.Set(id)
 }
 
 func (m *ManagedNode) onCrossSafeUpdate(pair types.DerivedBlockSealPair) {
@@ -242,7 +229,6 @@ func (m *ManagedNode) onCrossSafeUpdate(pair types.DerivedBlockSealPair) {
 		m.log.Warn("Node failed cross-safe updating", "err", err)
 		return
 	}
-	m.lastSentCrossSafe.Set(pairIDs)
 }
 
 func (m *ManagedNode) onFinalizedL2(seal types.BlockSeal) {
@@ -255,31 +241,33 @@ func (m *ManagedNode) onFinalizedL2(seal types.BlockSeal) {
 		m.log.Warn("Node failed finality updating", "err", err)
 		return
 	}
-	m.lastSentFinalized.Set(id)
 }
 
 func (m *ManagedNode) onUnsafeBlock(unsafeRef eth.BlockRef) {
 	m.log.Info("Node has new unsafe block", "unsafeBlock", unsafeRef)
-	ctx, cancel := context.WithTimeout(m.ctx, internalTimeout)
-	defer cancel()
-	if err := m.backend.UpdateLocalUnsafe(ctx, m.chainID, unsafeRef); err != nil {
-		m.log.Warn("Backend failed to pick up on new unsafe block", "unsafeBlock", unsafeRef, "err", err)
-		// TODO: if conflict error -> send reset to drop
-		// TODO: if future error -> send reset to rewind
-		// TODO: if out of order -> warn, just old data
-	}
+	m.emitter.Emit(superevents.LocalUnsafeReceivedEvent{
+		ChainID:        m.chainID,
+		NewLocalUnsafe: unsafeRef,
+	})
 }
 
 func (m *ManagedNode) onDerivationUpdate(pair types.DerivedBlockRefPair) {
 	m.log.Info("Node derived new block", "derived", pair.Derived,
 		"derivedParent", pair.Derived.ParentID(), "derivedFrom", pair.DerivedFrom)
-	ctx, cancel := context.WithTimeout(m.ctx, internalTimeout)
-	defer cancel()
-	if err := m.backend.UpdateLocalSafe(ctx, m.chainID, pair.DerivedFrom, pair.Derived); err != nil {
-		m.log.Warn("Backend failed to process local-safe update",
-			"derived", pair.Derived, "derivedFrom", pair.DerivedFrom, "err", err)
-		m.resetSignal(err, pair.DerivedFrom)
-	}
+	m.emitter.Emit(superevents.LocalDerivedEvent{
+		ChainID: m.chainID,
+		Derived: pair,
+	})
+	// TODO: keep synchronous local-safe DB update feedback?
+	// We'll still need more async ways of doing this for reorg handling.
+
+	//ctx, cancel := context.WithTimeout(m.ctx, internalTimeout)
+	//defer cancel()
+	//if err := m.backend.UpdateLocalSafe(ctx, m.chainID, pair.DerivedFrom, pair.Derived); err != nil {
+	//	m.log.Warn("Backend failed to process local-safe update",
+	//		"derived", pair.Derived, "derivedFrom", pair.DerivedFrom, "err", err)
+	//	m.resetSignal(err, pair.DerivedFrom)
+	//}
 }
 
 func (m *ManagedNode) resetSignal(errSignal error, l1Ref eth.BlockRef) {
@@ -358,36 +346,6 @@ func (m *ManagedNode) onExhaustL1Event(completed types.DerivedBlockRefPair) {
 		// but does not fit on the derivation state.
 		return
 	}
-	// now that the node has the next L1 block, we can add it to the database
-	// this ensures that only the L1 *or* the L2 ever increments in the derivation database,
-	// as RecordNewL1 will insert the new L1 block with the latest L2 block
-	ctx, cancel := context.WithTimeout(m.ctx, internalTimeout)
-	defer cancel()
-	err = m.backend.RecordNewL1(ctx, m.chainID, nextL1)
-	if err != nil {
-		m.log.Warn("Failed to record new L1 block", "l1Block", nextL1, "err", err)
-	}
-}
-
-func (m *ManagedNode) AwaitSentCrossUnsafeUpdate(ctx context.Context, minNum uint64) error {
-	_, err := m.lastSentCrossUnsafe.Catch(ctx, func(id eth.BlockID) bool {
-		return id.Number >= minNum
-	})
-	return err
-}
-
-func (m *ManagedNode) AwaitSentCrossSafeUpdate(ctx context.Context, minNum uint64) error {
-	_, err := m.lastSentCrossSafe.Catch(ctx, func(pair types.DerivedIDPair) bool {
-		return pair.Derived.Number >= minNum
-	})
-	return err
-}
-
-func (m *ManagedNode) AwaitSentFinalizedUpdate(ctx context.Context, minNum uint64) error {
-	_, err := m.lastSentFinalized.Catch(ctx, func(id eth.BlockID) bool {
-		return id.Number >= minNum
-	})
-	return err
 }
 
 func (m *ManagedNode) Close() error {

op-supervisor/supervisor/backend/syncnode/node_test.go

@@ -5,31 +5,39 @@ import (
 	"testing"
 	"time"
 
+	"github.com/stretchr/testify/require"
+
+	"github.com/ethereum/go-ethereum/log"
+
+	"github.com/ethereum-optimism/optimism/op-node/rollup/event"
 	"github.com/ethereum-optimism/optimism/op-service/eth"
 	"github.com/ethereum-optimism/optimism/op-service/testlog"
+	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend/superevents"
 	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/types"
-	"github.com/ethereum/go-ethereum/log"
-	"github.com/stretchr/testify/require"
 )
 
 func TestEventResponse(t *testing.T) {
 	chainID := types.ChainIDFromUInt64(1)
 	logger := testlog.Logger(t, log.LvlInfo)
 	syncCtrl := &mockSyncControl{}
-	db := &mockChainsDB{}
 	backend := &mockBackend{}
 
-	node := NewManagedNode(logger, chainID, syncCtrl, db, backend, false)
+	ex := event.NewGlobalSynchronous(context.Background())
+	eventSys := event.NewSystem(logger, ex)
+
+	mon := &eventMonitor{}
+	eventSys.Register("monitor", mon, event.DefaultRegisterOpts())
+
+	node := NewManagedNode(logger, chainID, syncCtrl, backend, false)
+	eventSys.Register("node", node, event.DefaultRegisterOpts())
+
+	emitter := eventSys.Register("test", nil, event.DefaultRegisterOpts())
 
 	crossUnsafe := 0
 	crossSafe := 0
 	finalized := 0
 
-	nodeUnsafe := 0
-	nodeDerivation := 0
 	nodeExhausted := 0
-	// recordL1 is called along with nodeExhausted
-	recordL1 := 0
 
 	// the node will call UpdateCrossUnsafe when a cross-unsafe event is received from the database
 	syncCtrl.updateCrossUnsafeFn = func(ctx context.Context, id eth.BlockID) error {
@@ -47,26 +55,12 @@ func TestEventResponse(t *testing.T) {
 		return nil
 	}
 
-	// track events from the node
-	// the node will call UpdateLocalUnsafe when a new unsafe block is received
-	backend.updateLocalUnsafeFn = func(ctx context.Context, chID types.ChainID, unsafe eth.BlockRef) error {
-		nodeUnsafe++
-		return nil
-	}
-	// the node will call UpdateLocalSafe when a new safe and L1 derivation source is received
-	backend.updateLocalSafeFn = func(ctx context.Context, chainID types.ChainID, derivedFrom eth.L1BlockRef, lastDerived eth.L1BlockRef) error {
-		nodeDerivation++
-		return nil
-	}
 	// the node will call ProvideL1 when the node is exhausted and needs a new L1 derivation source
 	syncCtrl.provideL1Fn = func(ctx context.Context, nextL1 eth.BlockRef) error {
 		nodeExhausted++
 		return nil
 	}
-	backend.recordL1Fn = func(ctx context.Context, chainID types.ChainID, ref eth.L1BlockRef) error {
-		recordL1++
-		return nil
-	}
+
 	// TODO(#13595): rework node-reset, and include testing for it here
 
 	node.Start()
@@ -74,9 +68,10 @@ func TestEventResponse(t *testing.T) {
 	// send events and continue to do so until at least one of each type has been received
 	require.Eventually(t, func() bool {
 		// send in one event of each type
-		db.subscribeCrossUnsafe.Send(types.BlockSeal{})
-		db.subscribeCrosSafe.Send(types.DerivedBlockSealPair{})
-		db.subscribeFinalized.Send(types.BlockSeal{})
+		emitter.Emit(superevents.CrossUnsafeUpdateEvent{ChainID: chainID})
+		emitter.Emit(superevents.CrossSafeUpdateEvent{ChainID: chainID})
+		emitter.Emit(superevents.FinalizedL2UpdateEvent{ChainID: chainID})
+
 		syncCtrl.subscribeEvents.Send(&types.ManagedEvent{
 			UnsafeBlock: &eth.BlockRef{Number: 1}})
 		syncCtrl.subscribeEvents.Send(&types.ManagedEvent{
@@ -84,14 +79,13 @@ func TestEventResponse(t *testing.T) {
 		syncCtrl.subscribeEvents.Send(&types.ManagedEvent{
 			ExhaustL1: &types.DerivedBlockRefPair{DerivedFrom: eth.BlockRef{Number: 1}, Derived: eth.BlockRef{Number: 2}}})
 
+		require.NoError(t, ex.Drain())
+
 		return crossUnsafe >= 1 &&
 			crossSafe >= 1 &&
 			finalized >= 1 &&
-			nodeUnsafe >= 1 &&
-			nodeDerivation >= 1 &&
+			mon.receivedLocalUnsafe >= 1 &&
+			mon.localDerived >= 1 &&
 			nodeExhausted >= 1
 	}, 4*time.Second, 250*time.Millisecond)
-
-	// recordL1 is called every time nodeExhausted is called
-	require.Equal(t, nodeExhausted, recordL1)
 }

op-supervisor/supervisor/service.go

@@ -5,15 +5,19 @@ import (
 	"errors"
 	"fmt"
 	"sync/atomic"
+	"time"
 
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/rpc"
 
+	"github.com/ethereum-optimism/optimism/op-node/rollup/event"
 	"github.com/ethereum-optimism/optimism/op-service/cliapp"
+	"github.com/ethereum-optimism/optimism/op-service/clock"
 	"github.com/ethereum-optimism/optimism/op-service/httputil"
 	opmetrics "github.com/ethereum-optimism/optimism/op-service/metrics"
 	"github.com/ethereum-optimism/optimism/op-service/oppprof"
 	oprpc "github.com/ethereum-optimism/optimism/op-service/rpc"
+	"github.com/ethereum-optimism/optimism/op-service/tasks"
 	"github.com/ethereum-optimism/optimism/op-supervisor/config"
 	"github.com/ethereum-optimism/optimism/op-supervisor/metrics"
 	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend"
@@ -34,6 +38,8 @@ type SupervisorService struct {
 
 	metrics metrics.Metricer
 
+	poller *tasks.Poller
+
 	backend Backend
 
 	pprofService *oppprof.Service
@@ -72,11 +78,21 @@ func (su *SupervisorService) initFromCLIConfig(ctx context.Context, cfg *config.
 }
 
 func (su *SupervisorService) initBackend(ctx context.Context, cfg *config.Config) error {
+	// In the future we may introduce other executors.
+	// For now, we just use a synchronous executor, and poll the drain function of it.
+	ex := event.NewGlobalSynchronous(ctx)
+	su.poller = tasks.NewPoller(func() {
+		if err := ex.Drain(); err != nil {
+			su.log.Warn("Failed to execute events", "err", err)
+		}
+	}, clock.SystemClock, time.Millisecond*100)
+
 	if cfg.MockRun {
 		su.backend = backend.NewMockBackend()
 		return nil
 	}
-	be, err := backend.NewSupervisorBackend(ctx, su.log, su.metrics, cfg)
+
+	be, err := backend.NewSupervisorBackend(ctx, su.log, su.metrics, cfg, ex)
 	if err != nil {
 		return fmt.Errorf("failed to create supervisor backend: %w", err)
 	}
@@ -179,6 +195,8 @@ func (su *SupervisorService) Start(ctx context.Context) error {
 		return fmt.Errorf("unable to start RPC server: %w", err)
 	}
 
+	su.poller.Start()
+
 	if err := su.backend.Start(ctx); err != nil {
 		return fmt.Errorf("unable to start backend: %w", err)
 	}
@@ -219,6 +237,10 @@ func (su *SupervisorService) Stop(ctx context.Context) error {
 		}
 	}
 	su.log.Info("JSON-RPC server stopped")
+	if su.poller != nil {
+		su.poller.Stop()
+	}
+	su.log.Info("Event processing stopped")
 	return result
 }