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package driver
import (
"context"
"encoding/json"
"errors"
"fmt"
"io"
gosync "sync"
"time"
"github.com/ethereum/go-ethereum/log"
"github.com/ethereum-optimism/optimism/op-node/eth"
"github.com/ethereum-optimism/optimism/op-node/rollup"
"github.com/ethereum-optimism/optimism/op-node/rollup/derive"
"github.com/ethereum-optimism/optimism/op-service/backoff"
)
// Deprecated: use eth.SyncStatus instead.
type SyncStatus = eth.SyncStatus
type Driver struct {
l1State L1StateIface
// The derivation pipeline is reset whenever we reorg.
// The derivation pipeline determines the new l2Safe.
derivation DerivationPipeline
// When the derivation pipeline is waiting for new data to do anything
idleDerivation bool
// Requests to block the event loop for synchronous execution to avoid reading an inconsistent state
stateReq chan chan struct{}
// Upon receiving a channel in this channel, the derivation pipeline is forced to be reset.
// It tells the caller that the reset occurred by closing the passed in channel.
forceReset chan chan struct{}
// Rollup config: rollup chain configuration
config *rollup.Config
// Driver config: verifier and sequencer settings
driverConfig *Config
// L1 Signals:
//
// Not all L1 blocks, or all changes, have to be signalled:
// the derivation process traverses the chain and handles reorgs as necessary,
// the driver just needs to be aware of the *latest* signals enough so to not
// lag behind actionable data.
l1HeadSig chan eth.L1BlockRef
l1SafeSig chan eth.L1BlockRef
l1FinalizedSig chan eth.L1BlockRef
// L2 Signals:
unsafeL2Payloads chan *eth.ExecutionPayload
l1 L1Chain
l2 L2Chain
l1OriginSelector L1OriginSelectorIface
sequencer SequencerIface
network Network // may be nil, network for is optional
metrics Metrics
log log.Logger
snapshotLog log.Logger
done chan struct{}
wg gosync.WaitGroup
}
// Start starts up the state loop.
// The loop will have been started iff err is not nil.
func (s *Driver) Start() error {
s.derivation.Reset()
s.wg.Add(1)
go s.eventLoop()
return nil
}
func (s *Driver) Close() error {
s.done <- struct{}{}
s.wg.Wait()
return nil
}
// OnL1Head signals the driver that the L1 chain changed the "unsafe" block,
// also known as head of the chain, or "latest".
func (s *Driver) OnL1Head(ctx context.Context, unsafe eth.L1BlockRef) error {
select {
case <-ctx.Done():
return ctx.Err()
case s.l1HeadSig <- unsafe:
return nil
}
}
// OnL1Safe signals the driver that the L1 chain changed the "safe",
// also known as the justified checkpoint (as seen on L1 beacon-chain).
func (s *Driver) OnL1Safe(ctx context.Context, safe eth.L1BlockRef) error {
select {
case <-ctx.Done():
return ctx.Err()
case s.l1SafeSig <- safe:
return nil
}
}
func (s *Driver) OnL1Finalized(ctx context.Context, finalized eth.L1BlockRef) error {
select {
case <-ctx.Done():
return ctx.Err()
case s.l1FinalizedSig <- finalized:
return nil
}
}
func (s *Driver) OnUnsafeL2Payload(ctx context.Context, payload *eth.ExecutionPayload) error {
select {
case <-ctx.Done():
return ctx.Err()
case s.unsafeL2Payloads <- payload:
return nil
}
}
// createNewL2Block builds a L2 block on top of the L2 Head (unsafe). Used by Sequencer nodes to
// construct new L2 blocks. Verifier nodes will use handleEpoch instead.
func (s *Driver) createNewL2Block(ctx context.Context) error {
l2Head := s.derivation.UnsafeL2Head()
l2Safe := s.derivation.SafeL2Head()
l2Finalized := s.derivation.Finalized()
l1Head := s.l1State.L1Head()
if l1Head == (eth.L1BlockRef{}) {
return derive.NewTemporaryError(errors.New("L1 Head in L1 State is not initizalited yet"))
}
// Figure out which L1 origin block we're going to be building on top of.
l1Origin, err := s.l1OriginSelector.FindL1Origin(ctx, l1Head, l2Head)
if err != nil {
s.log.Error("Error finding next L1 Origin", "err", err)
return err
}
// Rollup is configured to not start producing blocks until a specific L1 block has been
// reached. Don't produce any blocks until we're at that genesis block.
if l1Origin.Number < s.config.Genesis.L1.Number {
s.log.Info("Skipping block production because the next L1 Origin is behind the L1 genesis", "next", l1Origin.ID(), "genesis", s.config.Genesis.L1)
return nil
}
// Should never happen. Sequencer will halt if we get into this situation somehow.
nextL2Time := l2Head.Time + s.config.BlockTime
if nextL2Time < l1Origin.Time {
s.log.Error("Cannot build L2 block for time before L1 origin",
"l2Unsafe", l2Head, "nextL2Time", nextL2Time, "l1Origin", l1Origin, "l1OriginTime", l1Origin.Time)
return fmt.Errorf("cannot build L2 block on top %s for time %d before L1 origin %s at time %d",
l2Head, nextL2Time, l1Origin, l1Origin.Time)
}
// Actually create the new block.
newUnsafeL2Head, payload, err := s.sequencer.CreateNewBlock(ctx, l2Head, l2Safe.ID(), l2Finalized.ID(), l1Origin)
if err != nil {
s.log.Error("Could not extend chain as sequencer", "err", err, "l2_parent", l2Head, "l1_origin", l1Origin)
return err
}
// Update our L2 head block based on the new unsafe block we just generated.
s.derivation.SetUnsafeHead(newUnsafeL2Head)
s.log.Info("Sequenced new l2 block", "l2_unsafe", newUnsafeL2Head, "l1_origin", newUnsafeL2Head.L1Origin, "txs", len(payload.Transactions), "time", newUnsafeL2Head.Time)
s.metrics.CountSequencedTxs(len(payload.Transactions))
if s.network != nil {
if err := s.network.PublishL2Payload(ctx, payload); err != nil {
s.log.Warn("failed to publish newly created block", "id", payload.ID(), "err", err)
s.metrics.RecordPublishingError()
// publishing of unsafe data via p2p is optional. Errors are not severe enough to change/halt sequencing but should be logged and metered.
}
}
return nil
}
// the eventLoop responds to L1 changes and internal timers to produce L2 blocks.
func (s *Driver) eventLoop() {
defer s.wg.Done()
s.log.Info("State loop started")
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
// Start a ticker to produce L2 blocks at a constant rate. Ticker will only run if we're
// running in Sequencer mode.
var l2BlockCreationTickerCh <-chan time.Time
if s.driverConfig.SequencerEnabled {
l2BlockCreationTicker := time.NewTicker(time.Duration(s.config.BlockTime) * time.Second)
defer l2BlockCreationTicker.Stop()
l2BlockCreationTickerCh = l2BlockCreationTicker.C
}
// stepReqCh is used to request that the driver attempts to step forward by one L1 block.
stepReqCh := make(chan struct{}, 1)
// l2BlockCreationReqCh is used to request that the driver create a new L2 block. Only used if
// we're running in Sequencer mode, because otherwise we'll be deriving our blocks via the
// stepping process.
l2BlockCreationReqCh := make(chan struct{}, 1)
// reqL2BlockCreation requests that a block be created. Won't deadlock if the channel is full.
reqL2BlockCreation := func() {
select {
case l2BlockCreationReqCh <- struct{}{}:
// Don't deadlock if the channel is already full
default:
}
}
// channel, nil by default (not firing), but used to schedule re-attempts with delay
var delayedStepReq <-chan time.Time
// keep track of consecutive failed attempts, to adjust the backoff time accordingly
bOffStrategy := backoff.Exponential()
stepAttempts := 0
// step requests a derivation step to be taken. Won't deadlock if the channel is full.
step := func() {
select {
case stepReqCh <- struct{}{}:
// Don't deadlock if the channel is already full
default:
}
}
// reqStep requests a derivation step nicely, with a delay if this is a reattempt, or not at all if we already scheduled a reattempt.
reqStep := func() {
if stepAttempts > 0 {
// if this is not the first attempt, we re-schedule with a backoff, *without blocking other events*
if delayedStepReq == nil {
delay := bOffStrategy.Duration(stepAttempts)
s.log.Debug("scheduling re-attempt with delay", "attempts", stepAttempts, "delay", delay)
delayedStepReq = time.After(delay)
} else {
s.log.Debug("ignoring step request, already scheduled re-attempt after previous failure", "attempts", stepAttempts)
}
} else {
step()
}
}
// We call reqStep right away to finish syncing to the tip of the chain if we're behind.
// reqStep will also be triggered when the L1 head moves forward or if there was a reorg on the
// L1 chain that we need to handle.
reqStep()
for {
select {
case <-l2BlockCreationTickerCh:
s.log.Trace("L2 Creation Ticker")
s.snapshot("L2 Creation Ticker")
reqL2BlockCreation()
case <-l2BlockCreationReqCh:
s.snapshot("L2 Block Creation Request")
if !s.idleDerivation {
s.log.Warn("not creating block, node is deriving new l2 data", "head_l1", s.l1State.L1Head())
break
}
ctx, cancel := context.WithTimeout(ctx, 20*time.Minute)
err := s.createNewL2Block(ctx)
cancel()
if err != nil {
s.log.Error("Error creating new L2 block", "err", err)
s.metrics.RecordSequencingError()
break // if we fail, we wait for the next block creation trigger.
}
// We need to catch up to the next origin as quickly as possible. We can do this by
// requesting a new block ASAP instead of waiting for the next tick.
// We don't request a block if the confirmation depth is not met.
l2Head := s.derivation.UnsafeL2Head()
if wallClock := uint64(time.Now().Unix()); l2Head.Time+s.config.BlockTime <= wallClock {
s.log.Trace("Building another L2 block asap to catch up with wallclock",
"l2_unsafe", l2Head, "l2_unsafe_time", l2Head.Time, "wallclock", wallClock)
// But not too quickly to minimize busy-waiting for new blocks
time.AfterFunc(time.Millisecond*10, reqL2BlockCreation)
}
case payload := <-s.unsafeL2Payloads:
s.snapshot("New unsafe payload")
s.log.Info("Optimistically queueing unsafe L2 execution payload", "id", payload.ID())
s.derivation.AddUnsafePayload(payload)
s.metrics.RecordReceivedUnsafePayload(payload)
reqStep()
case newL1Head := <-s.l1HeadSig:
s.l1State.HandleNewL1HeadBlock(newL1Head)
reqStep() // a new L1 head may mean we have the data to not get an EOF again.
case newL1Safe := <-s.l1SafeSig:
s.l1State.HandleNewL1SafeBlock(newL1Safe)
// no step, justified L1 information does not do anything for L2 derivation or status
case newL1Finalized := <-s.l1FinalizedSig:
s.l1State.HandleNewL1FinalizedBlock(newL1Finalized)
s.derivation.Finalize(newL1Finalized)
reqStep() // we may be able to mark more L2 data as finalized now
case <-delayedStepReq:
delayedStepReq = nil
step()
case <-stepReqCh:
s.metrics.SetDerivationIdle(false)
s.idleDerivation = false
s.log.Debug("Derivation process step", "onto_origin", s.derivation.Origin(), "attempts", stepAttempts)
err := s.derivation.Step(context.Background())
stepAttempts += 1 // count as attempt by default. We reset to 0 if we are making healthy progress.
if err == io.EOF {
s.log.Debug("Derivation process went idle", "progress", s.derivation.Origin())
s.idleDerivation = true
stepAttempts = 0
s.metrics.SetDerivationIdle(true)
continue
} else if err != nil && errors.Is(err, derive.ErrReset) {
// If the pipeline corrupts, e.g. due to a reorg, simply reset it
s.log.Warn("Derivation pipeline is reset", "err", err)
s.derivation.Reset()
s.metrics.RecordPipelineReset()
continue
} else if err != nil && errors.Is(err, derive.ErrTemporary) {
s.log.Warn("Derivation process temporary error", "attempts", stepAttempts, "err", err)
reqStep()
continue
} else if err != nil && errors.Is(err, derive.ErrCritical) {
s.log.Error("Derivation process critical error", "err", err)
return
} else if err != nil && errors.Is(err, derive.NotEnoughData) {
stepAttempts = 0 // don't do a backoff for this error
reqStep()
continue
} else if err != nil {
s.log.Error("Derivation process error", "attempts", stepAttempts, "err", err)
reqStep()
continue
} else {
stepAttempts = 0
reqStep() // continue with the next step if we can
}
case respCh := <-s.stateReq:
respCh <- struct{}{}
case respCh := <-s.forceReset:
s.log.Warn("Derivation pipeline is manually reset")
s.derivation.Reset()
s.metrics.RecordPipelineReset()
close(respCh)
case <-s.done:
return
}
}
}
// ResetDerivationPipeline forces a reset of the derivation pipeline.
// It waits for the reset to occur. It simply unblocks the caller rather
// than fully cancelling the reset request upon a context cancellation.
func (s *Driver) ResetDerivationPipeline(ctx context.Context) error {
respCh := make(chan struct{}, 1)
select {
case <-ctx.Done():
return ctx.Err()
case s.forceReset <- respCh:
select {
case <-ctx.Done():
return ctx.Err()
case <-respCh:
return nil
}
}
}
// syncStatus returns the current sync status, and should only be called synchronously with
// the driver event loop to avoid retrieval of an inconsistent status.
func (s *Driver) syncStatus() *eth.SyncStatus {
return ð.SyncStatus{
CurrentL1: s.derivation.Origin(),
CurrentL1Finalized: s.derivation.FinalizedL1(),
HeadL1: s.l1State.L1Head(),
SafeL1: s.l1State.L1Safe(),
FinalizedL1: s.l1State.L1Finalized(),
UnsafeL2: s.derivation.UnsafeL2Head(),
SafeL2: s.derivation.SafeL2Head(),
FinalizedL2: s.derivation.Finalized(),
}
}
// SyncStatus blocks the driver event loop and captures the syncing status.
// If the event loop is too busy and the context expires, a context error is returned.
func (s *Driver) SyncStatus(ctx context.Context) (*eth.SyncStatus, error) {
wait := make(chan struct{})
select {
case s.stateReq <- wait:
resp := s.syncStatus()
<-wait
return resp, nil
case <-ctx.Done():
return nil, ctx.Err()
}
}
// BlockRefWithStatus blocks the driver event loop and captures the syncing status,
// along with an L2 block reference by number consistent with that same status.
// If the event loop is too busy and the context expires, a context error is returned.
func (s *Driver) BlockRefWithStatus(ctx context.Context, num uint64) (eth.L2BlockRef, *eth.SyncStatus, error) {
wait := make(chan struct{})
select {
case s.stateReq <- wait:
resp := s.syncStatus()
ref, err := s.l2.L2BlockRefByNumber(ctx, num)
<-wait
return ref, resp, err
case <-ctx.Done():
return eth.L2BlockRef{}, nil, ctx.Err()
}
}
// deferJSONString helps avoid a JSON-encoding performance hit if the snapshot logger does not run
type deferJSONString struct {
x any
}
func (v deferJSONString) String() string {
out, _ := json.Marshal(v.x)
return string(out)
}
func (s *Driver) snapshot(event string) {
s.snapshotLog.Info("Rollup State Snapshot",
"event", event,
"l1Head", deferJSONString{s.l1State.L1Head()},
"l1Current", deferJSONString{s.derivation.Origin()},
"l2Head", deferJSONString{s.derivation.UnsafeL2Head()},
"l2Safe", deferJSONString{s.derivation.SafeL2Head()},
"l2FinalizedHead", deferJSONString{s.derivation.Finalized()})
}