feat(op-dispute-mon): CLI Setup and Monitoring Metrics (#9371)

* feat(ctb): `useFaultProofs` runtime override (#9399)

* Add `useFaultProofs` runtime override

updates

* Update gas snapshot

* improve CI matrix names

* revert e2e changes

* feat(op-dispute-mon): cli setup with metrics

---------
Co-authored-by: clabby <ben@clab.by>

op-challenger/game/fault/contracts/faultdisputegame.go

@@ -18,6 +18,7 @@ var (
 	methodMaxGameDepth       = "maxGameDepth"
 	methodAbsolutePrestate   = "absolutePrestate"
 	methodStatus             = "status"
+	methodRootClaim          = "rootClaim"
 	methodClaimCount         = "claimDataLen"
 	methodClaim              = "claimData"
 	methodL1Head             = "l1Head"
@@ -78,6 +79,27 @@ func (c *FaultDisputeGameContract) GetBlockRange(ctx context.Context) (prestateB
 	return
 }
 
+// GetGameMetadata returns the game's L2 block number, root claim, and status.
+func (c *FaultDisputeGameContract) GetGameMetadata(ctx context.Context) (uint64, common.Hash, gameTypes.GameStatus, error) {
+	results, err := c.multiCaller.Call(ctx, batching.BlockLatest,
+		c.contract.Call(methodL2BlockNumber),
+		c.contract.Call(methodRootClaim),
+		c.contract.Call(methodStatus))
+	if err != nil {
+		return 0, common.Hash{}, 0, fmt.Errorf("failed to retrieve game metadata: %w", err)
+	}
+	if len(results) != 3 {
+		return 0, common.Hash{}, 0, fmt.Errorf("expected 3 results but got %v", len(results))
+	}
+	l2BlockNumber := results[0].GetBigInt(0).Uint64()
+	rootClaim := results[1].GetHash(0)
+	status, err := gameTypes.GameStatusFromUint8(results[2].GetUint8(0))
+	if err != nil {
+		return 0, common.Hash{}, 0, fmt.Errorf("failed to convert game status: %w", err)
+	}
+	return l2BlockNumber, rootClaim, status, nil
+}
+
 func (c *FaultDisputeGameContract) GetGenesisOutputRoot(ctx context.Context) (common.Hash, error) {
 	genesisOutputRoot, err := c.multiCaller.SingleCall(ctx, batching.BlockLatest, c.contract.Call(methodGenesisOutputRoot))
 	if err != nil {

op-challenger/game/fault/contracts/faultdisputegame_test.go

@@ -278,6 +278,21 @@ func TestGetSplitDepth(t *testing.T) {
 	require.Equal(t, expectedSplitDepth, splitDepth)
 }
 
+func TestGetGameMetadata(t *testing.T) {
+	stubRpc, contract := setupFaultDisputeGameTest(t)
+	expectedL2BlockNumber := uint64(123)
+	expectedRootClaim := common.Hash{0x01, 0x02}
+	expectedStatus := types.GameStatusChallengerWon
+	stubRpc.SetResponse(fdgAddr, methodL2BlockNumber, batching.BlockLatest, nil, []interface{}{new(big.Int).SetUint64(expectedL2BlockNumber)})
+	stubRpc.SetResponse(fdgAddr, methodRootClaim, batching.BlockLatest, nil, []interface{}{expectedRootClaim})
+	stubRpc.SetResponse(fdgAddr, methodStatus, batching.BlockLatest, nil, []interface{}{expectedStatus})
+	l2BlockNumber, rootClaim, status, err := contract.GetGameMetadata(context.Background())
+	require.NoError(t, err)
+	require.Equal(t, expectedL2BlockNumber, l2BlockNumber)
+	require.Equal(t, expectedRootClaim, rootClaim)
+	require.Equal(t, expectedStatus, status)
+}
+
 func TestGetGenesisOutputRoot(t *testing.T) {
 	stubRpc, contract := setupFaultDisputeGameTest(t)
 	expectedOutputRoot := common.HexToHash("0x1234")

op-challenger/game/fault/register.go

@@ -19,11 +19,6 @@ import (
 	"github.com/ethereum/go-ethereum/log"
 )
 
-var (
-	cannonGameType   = uint32(0)
-	alphabetGameType = uint32(255)
-)
-
 type CloseFunc func()
 
 type Registry interface {
@@ -102,16 +97,16 @@ func registerAlphabet(
 		genesisValidator := NewPrestateValidator(contract.GetGenesisOutputRoot, prestateProvider)
 		return NewGamePlayer(ctx, cl, logger, m, dir, game.Proxy, txSender, contract, []Validator{prestateValidator, genesisValidator}, creator)
 	}
-	oracle, err := createOracle(ctx, gameFactory, caller, alphabetGameType)
+	oracle, err := createOracle(ctx, gameFactory, caller, faultTypes.AlphabetGameType)
 	if err != nil {
 		return err
 	}
-	registry.RegisterGameType(alphabetGameType, playerCreator, oracle)
+	registry.RegisterGameType(faultTypes.AlphabetGameType, playerCreator, oracle)
 
 	contractCreator := func(game types.GameMetadata) (claims.BondContract, error) {
 		return contracts.NewFaultDisputeGameContract(game.Proxy, caller)
 	}
-	registry.RegisterBondContract(alphabetGameType, contractCreator)
+	registry.RegisterBondContract(faultTypes.AlphabetGameType, contractCreator)
 	return nil
 }
 
@@ -169,15 +164,15 @@ func registerCannon(
 		genesisValidator := NewPrestateValidator(contract.GetGenesisOutputRoot, prestateProvider)
 		return NewGamePlayer(ctx, cl, logger, m, dir, game.Proxy, txSender, contract, []Validator{prestateValidator, genesisValidator}, creator)
 	}
-	oracle, err := createOracle(ctx, gameFactory, caller, cannonGameType)
+	oracle, err := createOracle(ctx, gameFactory, caller, faultTypes.CannonGameType)
 	if err != nil {
 		return err
 	}
-	registry.RegisterGameType(cannonGameType, playerCreator, oracle)
+	registry.RegisterGameType(faultTypes.CannonGameType, playerCreator, oracle)
 
 	contractCreator := func(game types.GameMetadata) (claims.BondContract, error) {
 		return contracts.NewFaultDisputeGameContract(game.Proxy, caller)
 	}
-	registry.RegisterBondContract(cannonGameType, contractCreator)
+	registry.RegisterBondContract(faultTypes.CannonGameType, contractCreator)
 	return nil
 }

op-challenger/game/fault/types/types.go

@@ -18,6 +18,11 @@ var (
 	NoLocalContext = common.Hash{}
 )
 
+const (
+	CannonGameType   uint32 = 0
+	AlphabetGameType uint32 = 255
+)
+
 type ClockReader interface {
 	Now() time.Time
 }

op-dispute-mon/config/config.go

@@ -3,27 +3,49 @@ package config
 import (
 	"errors"
 	"fmt"
+	"time"
 
 	opmetrics "github.com/ethereum-optimism/optimism/op-service/metrics"
 	"github.com/ethereum-optimism/optimism/op-service/oppprof"
+
+	"github.com/ethereum/go-ethereum/common"
 )
 
 var (
 	ErrMissingL1EthRPC           = errors.New("missing l1 eth rpc url")
+	ErrMissingGameFactoryAddress = errors.New("missing game factory address")
+)
+
+const (
+	// DefaultGameWindow is the default maximum time duration in the past
+	// to look for games to monitor. The default value is 11 days, which
+	// is a 4 day resolution buffer plus the 7 day game finalization window.
+	DefaultGameWindow = time.Duration(11 * 24 * time.Hour)
+	// DefaultMonitorInterval is the default interval at which the dispute
+	// monitor will check for new games to monitor.
+	DefaultMonitorInterval = time.Second * 30
 )
 
 // Config is a well typed config that is parsed from the CLI params.
 // It also contains config options for auxiliary services.
 type Config struct {
 	L1EthRpc           string         // L1 RPC Url
+	GameFactoryAddress common.Address // Address of the dispute game factory
+	MonitorInterval    time.Duration  // Frequency to check for new games to monitor.
+	GameWindow         time.Duration  // Maximum window to look for games to monitor.
 
 	MetricsConfig opmetrics.CLIConfig
 	PprofConfig   oppprof.CLIConfig
 }
 
-func NewConfig(l1EthRpc string) Config {
+func NewConfig(gameFactoryAddress common.Address, l1EthRpc string) Config {
 	return Config{
 		L1EthRpc:           l1EthRpc,
+		GameFactoryAddress: gameFactoryAddress,
+
+		MonitorInterval: DefaultMonitorInterval,
+		GameWindow:      DefaultGameWindow,
+
 		MetricsConfig: opmetrics.DefaultCLIConfig(),
 		PprofConfig:   oppprof.DefaultCLIConfig(),
 	}
@@ -33,6 +55,9 @@ func (c Config) Check() error {
 	if c.L1EthRpc == "" {
 		return ErrMissingL1EthRPC
 	}
+	if c.GameFactoryAddress == (common.Address{}) {
+		return ErrMissingGameFactoryAddress
+	}
 	if err := c.MetricsConfig.Check(); err != nil {
 		return fmt.Errorf("metrics config: %w", err)
 	}

op-dispute-mon/config/config_test.go

@@ -4,14 +4,21 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/require"
+
+	"github.com/ethereum/go-ethereum/common"
 )
 
 var (
 	validL1EthRpc           = "http://localhost:8545"
+	validGameFactoryAddress = common.Address{0x23}
 )
 
 func validConfig() Config {
-	return NewConfig(validL1EthRpc)
+	return NewConfig(validGameFactoryAddress, validL1EthRpc)
+}
+
+func TestValidConfigIsValid(t *testing.T) {
+	require.NoError(t, validConfig().Check())
 }
 
 func TestL1EthRpcRequired(t *testing.T) {
@@ -19,3 +26,9 @@ func TestL1EthRpcRequired(t *testing.T) {
 	config.L1EthRpc = ""
 	require.ErrorIs(t, config.Check(), ErrMissingL1EthRPC)
 }
+
+func TestGameFactoryAddressRequired(t *testing.T) {
+	config := validConfig()
+	config.GameFactoryAddress = common.Address{}
+	require.ErrorIs(t, config.Check(), ErrMissingGameFactoryAddress)
+}

op-dispute-mon/flags/flags.go

@@ -27,16 +27,38 @@ var (
 		Usage:   "HTTP provider URL for L1.",
 		EnvVars: prefixEnvVars("L1_ETH_RPC"),
 	}
+	FactoryAddressFlag = &cli.StringFlag{
+		Name:    "game-factory-address",
+		Usage:   "Address of the fault game factory contract.",
+		EnvVars: prefixEnvVars("GAME_FACTORY_ADDRESS"),
+	}
 	// Optional Flags
+	MonitorIntervalFlag = &cli.DurationFlag{
+		Name:    "monitor-interval",
+		Usage:   "The interval at which the dispute monitor will check for new games to monitor.",
+		EnvVars: prefixEnvVars("MONITOR_INTERVAL"),
+		Value:   config.DefaultMonitorInterval,
+	}
+	GameWindowFlag = &cli.DurationFlag{
+		Name: "game-window",
+		Usage: "The time window which the monitor will consider games to report on. " +
+			"This should include a bond claim buffer for games outside the maximum game duration.",
+		EnvVars: prefixEnvVars("GAME_WINDOW"),
+		Value:   config.DefaultGameWindow,
+	}
 )
 
 // requiredFlags are checked by [CheckRequired]
 var requiredFlags = []cli.Flag{
 	L1EthRpcFlag,
+	FactoryAddressFlag,
 }
 
 // optionalFlags is a list of unchecked cli flags
-var optionalFlags = []cli.Flag{}
+var optionalFlags = []cli.Flag{
+	MonitorIntervalFlag,
+	GameWindowFlag,
+}
 
 func init() {
 	optionalFlags = append(optionalFlags, oplog.CLIFlags(envVarPrefix)...)
@@ -63,12 +85,21 @@ func NewConfigFromCLI(ctx *cli.Context) (*config.Config, error) {
 	if err := CheckRequired(ctx); err != nil {
 		return nil, err
 	}
+	gameFactoryAddress, err := opservice.ParseAddress(ctx.String(FactoryAddressFlag.Name))
+	if err != nil {
+		return nil, err
+	}
 
 	metricsConfig := opmetrics.ReadCLIConfig(ctx)
 	pprofConfig := oppprof.ReadCLIConfig(ctx)
 
 	return &config.Config{
 		L1EthRpc:           ctx.String(L1EthRpcFlag.Name),
+		GameFactoryAddress: gameFactoryAddress,
+
+		MonitorInterval: ctx.Duration(MonitorIntervalFlag.Name),
+		GameWindow:      ctx.Duration(GameWindowFlag.Name),
+
 		MetricsConfig: metricsConfig,
 		PprofConfig:   pprofConfig,
 	}, nil

op-dispute-mon/metrics/metrics.go

@@ -19,6 +19,8 @@ type Metricer interface {
 	RecordInfo(version string)
 	RecordUp()
 
+	RecordGamesStatus(inProgress, defenderWon, challengerWon int)
+
 	caching.Metrics
 }
 
@@ -34,6 +36,8 @@ type Metrics struct {
 
 	info prometheus.GaugeVec
 	up   prometheus.Gauge
+
+	trackedGames prometheus.GaugeVec
 }
 
 func (m *Metrics) Registry() *prometheus.Registry {
@@ -65,6 +69,13 @@ func NewMetrics() *Metrics {
 			Name:      "up",
 			Help:      "1 if the op-challenger has finished starting up",
 		}),
+		trackedGames: *factory.NewGaugeVec(prometheus.GaugeOpts{
+			Namespace: Namespace,
+			Name:      "tracked_games",
+			Help:      "Number of games being tracked by the challenger",
+		}, []string{
+			"status",
+		}),
 	}
 }
 
@@ -95,3 +106,9 @@ func (m *Metrics) RecordUp() {
 func (m *Metrics) Document() []opmetrics.DocumentedMetric {
 	return m.factory.Document()
 }
+
+func (m *Metrics) RecordGamesStatus(inProgress, defenderWon, challengerWon int) {
+	m.trackedGames.WithLabelValues("in_progress").Set(float64(inProgress))
+	m.trackedGames.WithLabelValues("defender_won").Set(float64(defenderWon))
+	m.trackedGames.WithLabelValues("challenger_won").Set(float64(challengerWon))
+}

op-dispute-mon/metrics/noop.go

@@ -9,3 +9,5 @@ func (*NoopMetricsImpl) RecordUp()                 {}
 
 func (*NoopMetricsImpl) CacheAdd(_ string, _ int, _ bool) {}
 func (*NoopMetricsImpl) CacheGet(_ string, _ bool)        {}
+
+func (*NoopMetricsImpl) RecordGamesStatus(inProgress, defenderWon, challengerWon int) {}

op-dispute-mon/mon/metadata.go

+package mon
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/ethereum/go-ethereum/common"
+
+	"github.com/ethereum-optimism/optimism/op-challenger/game/fault/contracts"
+	faultTypes "github.com/ethereum-optimism/optimism/op-challenger/game/fault/types"
+	"github.com/ethereum-optimism/optimism/op-challenger/game/types"
+	"github.com/ethereum-optimism/optimism/op-service/sources/batching"
+	"github.com/ethereum-optimism/optimism/op-service/sources/caching"
+)
+
+const metricsLabel = "binding_creator"
+
+type MetadataLoader interface {
+	GetGameMetadata(context.Context) (uint64, common.Hash, types.GameStatus, error)
+}
+
+type metadataCreator struct {
+	cache  *caching.LRUCache[common.Address, *contracts.FaultDisputeGameContract]
+	caller *batching.MultiCaller
+}
+
+func NewMetadataCreator(m caching.Metrics, caller *batching.MultiCaller) *metadataCreator {
+	return &metadataCreator{
+		caller: caller,
+		cache:  caching.NewLRUCache[common.Address, *contracts.FaultDisputeGameContract](m, metricsLabel, 100),
+	}
+}
+
+func (m *metadataCreator) CreateContract(game types.GameMetadata) (MetadataLoader, error) {
+	if fdg, ok := m.cache.Get(game.Proxy); ok {
+		return fdg, nil
+	}
+	switch game.GameType {
+	case faultTypes.CannonGameType, faultTypes.AlphabetGameType:
+		fdg, err := contracts.NewFaultDisputeGameContract(game.Proxy, m.caller)
+		if err != nil {
+			return nil, fmt.Errorf("failed to create FaultDisputeGameContract: %w", err)
+		}
+		m.cache.Add(game.Proxy, fdg)
+		return fdg, nil
+	default:
+		return nil, fmt.Errorf("unsupported game type: %d", game.GameType)
+	}
+}

op-dispute-mon/mon/metadata_test.go

+package mon
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common"
+
+	"github.com/ethereum-optimism/optimism/op-bindings/bindings"
+	faultTypes "github.com/ethereum-optimism/optimism/op-challenger/game/fault/types"
+	"github.com/ethereum-optimism/optimism/op-challenger/game/types"
+	"github.com/ethereum-optimism/optimism/op-service/sources/batching"
+	batchingTest "github.com/ethereum-optimism/optimism/op-service/sources/batching/test"
+	"github.com/stretchr/testify/require"
+)
+
+var (
+	fdgAddr = common.HexToAddress("0x24112842371dFC380576ebb09Ae16Cb6B6caD7CB")
+)
+
+func TestMetadataCreator_CreateContract(t *testing.T) {
+	tests := []struct {
+		name        string
+		game        types.GameMetadata
+		expectedErr error
+	}{
+		{
+			name: "validCannonGameType",
+			game: types.GameMetadata{GameType: faultTypes.CannonGameType, Proxy: fdgAddr},
+		},
+		{
+			name: "validAlphabetGameType",
+			game: types.GameMetadata{GameType: faultTypes.AlphabetGameType, Proxy: fdgAddr},
+		},
+		{
+			name:        "InvalidGameType",
+			game:        types.GameMetadata{GameType: 2, Proxy: fdgAddr},
+			expectedErr: fmt.Errorf("unsupported game type: 2"),
+		},
+	}
+
+	for _, test := range tests {
+		test := test
+		t.Run(test.name, func(t *testing.T) {
+			caller, metrics := setupMetadataLoaderTest(t)
+			creator := NewMetadataCreator(metrics, caller)
+			_, err := creator.CreateContract(test.game)
+			require.Equal(t, test.expectedErr, err)
+			if test.expectedErr == nil {
+				require.Equal(t, 1, metrics.cacheAddCalls)
+				require.Equal(t, 1, metrics.cacheGetCalls)
+			}
+			_, err = creator.CreateContract(test.game)
+			require.Equal(t, test.expectedErr, err)
+			if test.expectedErr == nil {
+				require.Equal(t, 1, metrics.cacheAddCalls)
+				require.Equal(t, 2, metrics.cacheGetCalls)
+			}
+		})
+	}
+}
+
+func setupMetadataLoaderTest(t *testing.T) (*batching.MultiCaller, *mockCacheMetrics) {
+	fdgAbi, err := bindings.FaultDisputeGameMetaData.GetAbi()
+	require.NoError(t, err)
+	stubRpc := batchingTest.NewAbiBasedRpc(t, fdgAddr, fdgAbi)
+	caller := batching.NewMultiCaller(stubRpc, batching.DefaultBatchSize)
+	return caller, &mockCacheMetrics{}
+}
+
+type mockCacheMetrics struct {
+	cacheAddCalls int
+	cacheGetCalls int
+}
+
+func (m *mockCacheMetrics) CacheAdd(_ string, _ int, _ bool) {
+	m.cacheAddCalls++
+}
+func (m *mockCacheMetrics) CacheGet(_ string, _ bool) {
+	m.cacheGetCalls++
+}

op-dispute-mon/mon/monitor.go

+package mon
+
+import (
+	"context"
+	"fmt"
+	"math/big"
+	"time"
+
+	"github.com/ethereum-optimism/optimism/op-challenger/game/types"
+	"github.com/ethereum-optimism/optimism/op-service/clock"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/log"
+)
+
+type blockNumberFetcher func(ctx context.Context) (uint64, error)
+type blockHashFetcher func(ctx context.Context, number *big.Int) (common.Hash, error)
+
+// gameSource loads information about the games available to play
+type gameSource interface {
+	GetGamesAtOrAfter(ctx context.Context, blockHash common.Hash, earliestTimestamp uint64) ([]types.GameMetadata, error)
+}
+
+type MonitorMetricer interface {
+	RecordGamesStatus(inProgress, defenderWon, challengerWon int)
+}
+
+type MetadataCreator interface {
+	CreateContract(game types.GameMetadata) (MetadataLoader, error)
+}
+
+type gameMonitor struct {
+	logger  log.Logger
+	metrics MonitorMetricer
+
+	ctx    context.Context
+	cancel context.CancelFunc
+
+	clock            clock.Clock
+	monitorInterval  time.Duration
+	done             chan struct{}
+	source           gameSource
+	metadata         MetadataCreator
+	gameWindow       time.Duration
+	fetchBlockNumber blockNumberFetcher
+	fetchBlockHash   blockHashFetcher
+}
+
+func newGameMonitor(
+	ctx context.Context,
+	logger log.Logger,
+	metrics MonitorMetricer,
+	cl clock.Clock,
+	monitorInterval time.Duration,
+	source gameSource,
+	metadata MetadataCreator,
+	gameWindow time.Duration,
+	fetchBlockNumber blockNumberFetcher,
+	fetchBlockHash blockHashFetcher,
+) *gameMonitor {
+	return &gameMonitor{
+		logger:           logger,
+		metrics:          metrics,
+		ctx:              ctx,
+		clock:            cl,
+		done:             make(chan struct{}),
+		monitorInterval:  monitorInterval,
+		source:           source,
+		metadata:         metadata,
+		gameWindow:       gameWindow,
+		fetchBlockNumber: fetchBlockNumber,
+		fetchBlockHash:   fetchBlockHash,
+	}
+}
+
+func (m *gameMonitor) minGameTimestamp() uint64 {
+	if m.gameWindow.Seconds() == 0 {
+		return 0
+	}
+	// time: "To compute t-d for a duration d, use t.Add(-d)."
+	// https://pkg.go.dev/time#Time.Sub
+	if m.clock.Now().Unix() > int64(m.gameWindow.Seconds()) {
+		return uint64(m.clock.Now().Add(-m.gameWindow).Unix())
+	}
+	return 0
+}
+
+func (m *gameMonitor) monitorGames() error {
+	blockNumber, err := m.fetchBlockNumber(m.ctx)
+	if err != nil {
+		return fmt.Errorf("Failed to fetch block number: %w", err)
+	}
+	m.logger.Debug("Fetched block number", "blockNumber", blockNumber)
+	blockHash, err := m.fetchBlockHash(context.Background(), new(big.Int).SetUint64(blockNumber))
+	if err != nil {
+		return fmt.Errorf("Failed to fetch block hash: %w", err)
+	}
+	games, err := m.source.GetGamesAtOrAfter(m.ctx, blockHash, m.minGameTimestamp())
+	if err != nil {
+		return fmt.Errorf("failed to load games: %w", err)
+	}
+	return m.recordGamesStatus(m.ctx, games)
+}
+
+func (m *gameMonitor) recordGamesStatus(ctx context.Context, games []types.GameMetadata) error {
+	inProgress, defenderWon, challengerWon := 0, 0, 0
+	for _, game := range games {
+		loader, err := m.metadata.CreateContract(game)
+		if err != nil {
+			m.logger.Error("Failed to create contract", "err", err)
+			continue
+		}
+		_, _, status, err := loader.GetGameMetadata(ctx)
+		if err != nil {
+			m.logger.Error("Failed to get game metadata", "err", err)
+			continue
+		}
+		switch status {
+		case types.GameStatusInProgress:
+			inProgress++
+		case types.GameStatusDefenderWon:
+			defenderWon++
+		case types.GameStatusChallengerWon:
+			challengerWon++
+		}
+	}
+	m.metrics.RecordGamesStatus(inProgress, defenderWon, challengerWon)
+	return nil
+}
+
+func (m *gameMonitor) loop() {
+	ticker := m.clock.NewTicker(m.monitorInterval)
+	defer ticker.Stop()
+	for {
+		select {
+		case <-ticker.Ch():
+			if err := m.monitorGames(); err != nil {
+				m.logger.Error("Failed to monitor games", "err", err)
+			}
+		case <-m.done:
+			m.logger.Info("Stopping game monitor")
+			return
+		}
+	}
+}
+
+func (m *gameMonitor) StartMonitoring() {
+	// Setup the cancellation only if it's not already set.
+	// This prevents overwriting the context and cancel function
+	// if, for example, this function is called multiple times.
+	if m.cancel == nil {
+		ctx, cancel := context.WithCancel(m.ctx)
+		m.ctx = ctx
+		m.cancel = cancel
+	}
+	m.logger.Info("Starting game monitor")
+	go m.loop()
+}
+
+func (m *gameMonitor) StopMonitoring() {
+	m.logger.Info("Stopping game monitor")
+	if m.cancel != nil {
+		m.cancel()
+		m.cancel = nil
+	}
+	close(m.done)
+}

op-dispute-mon/mon/monitor_test.go

+package mon
+
+import (
+	"context"
+	"errors"
+	"math/big"
+	"testing"
+	"time"
+
+	"github.com/ethereum-optimism/optimism/op-challenger/game/types"
+	"github.com/ethereum-optimism/optimism/op-service/clock"
+	"github.com/ethereum-optimism/optimism/op-service/testlog"
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/log"
+	"github.com/stretchr/testify/require"
+)
+
+var (
+	mockErr = errors.New("mock error")
+)
+
+func TestMonitor_MinGameTimestamp(t *testing.T) {
+	t.Parallel()
+
+	t.Run("zero game window returns zero", func(t *testing.T) {
+		monitor, _, _, _ := setupMonitorTest(t)
+		monitor.gameWindow = time.Duration(0)
+		require.Equal(t, monitor.minGameTimestamp(), uint64(0))
+	})
+
+	t.Run("non-zero game window with zero clock", func(t *testing.T) {
+		monitor, _, _, _ := setupMonitorTest(t)
+		monitor.gameWindow = time.Minute
+		monitor.clock = clock.NewDeterministicClock(time.Unix(0, 0))
+		require.Equal(t, uint64(0), monitor.minGameTimestamp())
+	})
+
+	t.Run("minimum computed correctly", func(t *testing.T) {
+		monitor, _, _, _ := setupMonitorTest(t)
+		monitor.gameWindow = time.Minute
+		frozen := time.Unix(int64(time.Hour.Seconds()), 0)
+		monitor.clock = clock.NewDeterministicClock(frozen)
+		expected := uint64(frozen.Add(-time.Minute).Unix())
+		require.Equal(t, monitor.minGameTimestamp(), expected)
+	})
+}
+
+func TestMonitor_RecordGamesStatus(t *testing.T) {
+	tests := []struct {
+		name    string
+		games   []types.GameMetadata
+		status  func(loader *mockMetadataLoader)
+		creator func(creator *mockMetadataCreator)
+		metrics func(m *stubMonitorMetricer)
+	}{
+		{
+			name:  "NoGames",
+			games: []types.GameMetadata{},
+			metrics: func(m *stubMonitorMetricer) {
+				require.Equal(t, 0, m.inProgress)
+				require.Equal(t, 0, m.defenderWon)
+				require.Equal(t, 0, m.challengerWon)
+			},
+		},
+		{
+			name:  "InProgress",
+			games: []types.GameMetadata{{}},
+			metrics: func(m *stubMonitorMetricer) {
+				require.Equal(t, 1, m.inProgress)
+				require.Equal(t, 0, m.defenderWon)
+				require.Equal(t, 0, m.challengerWon)
+			},
+		},
+		{
+			name:  "DefenderWon",
+			games: []types.GameMetadata{{}},
+			status: func(loader *mockMetadataLoader) {
+				loader.status = types.GameStatusDefenderWon
+			},
+			metrics: func(m *stubMonitorMetricer) {
+				require.Equal(t, 0, m.inProgress)
+				require.Equal(t, 1, m.defenderWon)
+				require.Equal(t, 0, m.challengerWon)
+			},
+		},
+		{
+			name:  "ChallengerWon",
+			games: []types.GameMetadata{{}},
+			status: func(loader *mockMetadataLoader) {
+				loader.status = types.GameStatusChallengerWon
+			},
+			metrics: func(m *stubMonitorMetricer) {
+				require.Equal(t, 0, m.inProgress)
+				require.Equal(t, 0, m.defenderWon)
+				require.Equal(t, 1, m.challengerWon)
+			},
+		},
+		{
+			name:  "MetadataLoaderError",
+			games: []types.GameMetadata{{}},
+			status: func(loader *mockMetadataLoader) {
+				loader.err = mockErr
+			},
+			metrics: func(m *stubMonitorMetricer) {
+				require.Equal(t, 0, m.inProgress)
+				require.Equal(t, 0, m.defenderWon)
+				require.Equal(t, 0, m.challengerWon)
+			},
+		},
+		{
+			name:    "MetadataCreatorError",
+			games:   []types.GameMetadata{{}},
+			creator: func(creator *mockMetadataCreator) { creator.err = mockErr },
+			metrics: func(m *stubMonitorMetricer) {
+				require.Equal(t, 0, m.inProgress)
+				require.Equal(t, 0, m.defenderWon)
+				require.Equal(t, 0, m.challengerWon)
+			},
+		},
+	}
+
+	for _, test := range tests {
+		test := test
+		t.Run(test.name, func(t *testing.T) {
+			monitor, _, metrics, creator := setupMonitorTest(t)
+			if test.status != nil {
+				test.status(creator.loader)
+			}
+			if test.creator != nil {
+				test.creator(creator)
+			}
+			err := monitor.recordGamesStatus(context.Background(), test.games)
+			require.NoError(t, err) // All errors are handled gracefully
+			test.metrics(metrics)
+		})
+	}
+}
+
+func TestMonitor_MonitorGames(t *testing.T) {
+	t.Parallel()
+
+	t.Run("FailedFetchBlocknumber", func(t *testing.T) {
+		monitor, _, _, _ := setupMonitorTest(t)
+		boom := errors.New("boom")
+		monitor.fetchBlockNumber = func(ctx context.Context) (uint64, error) {
+			return 0, boom
+		}
+		err := monitor.monitorGames()
+		require.ErrorIs(t, err, boom)
+	})
+
+	t.Run("FailedFetchBlockHash", func(t *testing.T) {
+		monitor, _, _, _ := setupMonitorTest(t)
+		boom := errors.New("boom")
+		monitor.fetchBlockHash = func(ctx context.Context, number *big.Int) (common.Hash, error) {
+			return common.Hash{}, boom
+		}
+		err := monitor.monitorGames()
+		require.ErrorIs(t, err, boom)
+	})
+
+	t.Run("NoGames", func(t *testing.T) {
+		monitor, source, _, creator := setupMonitorTest(t)
+		source.games = []types.GameMetadata{}
+		err := monitor.monitorGames()
+		require.NoError(t, err)
+		require.Equal(t, 0, creator.calls)
+	})
+
+	t.Run("CreatorErrorsHandled", func(t *testing.T) {
+		monitor, source, _, creator := setupMonitorTest(t)
+		source.games = []types.GameMetadata{{}}
+		creator.err = errors.New("boom")
+		err := monitor.monitorGames()
+		require.NoError(t, err)
+		require.Equal(t, 1, creator.calls)
+	})
+
+	t.Run("Success", func(t *testing.T) {
+		monitor, source, metrics, _ := setupMonitorTest(t)
+		source.games = []types.GameMetadata{{}, {}, {}}
+		err := monitor.monitorGames()
+		require.NoError(t, err)
+		require.Equal(t, len(source.games), metrics.inProgress)
+	})
+}
+
+func TestMonitor_StartMonitoring(t *testing.T) {
+	t.Run("Monitors games", func(t *testing.T) {
+		addr1 := common.Address{0xaa}
+		addr2 := common.Address{0xbb}
+		monitor, source, metrics, _ := setupMonitorTest(t)
+		source.games = []types.GameMetadata{newFDG(addr1, 9999), newFDG(addr2, 9999)}
+		source.maxSuccess = len(source.games) // Only allow two successful fetches
+
+		monitor.StartMonitoring()
+		require.Eventually(t, func() bool {
+			return metrics.inProgress == 2
+		}, time.Second, 50*time.Millisecond)
+		monitor.StopMonitoring()
+		require.Equal(t, len(source.games), metrics.inProgress) // Each game's status is recorded twice
+	})
+
+	t.Run("Fails to monitor games", func(t *testing.T) {
+		monitor, source, metrics, _ := setupMonitorTest(t)
+		source.fetchErr = errors.New("boom")
+
+		monitor.StartMonitoring()
+		require.Eventually(t, func() bool {
+			return source.calls > 0
+		}, time.Second, 50*time.Millisecond)
+		monitor.StopMonitoring()
+		require.Equal(t, 0, metrics.inProgress)
+		require.Equal(t, 0, metrics.defenderWon)
+		require.Equal(t, 0, metrics.challengerWon)
+	})
+}
+
+func newFDG(proxy common.Address, timestamp uint64) types.GameMetadata {
+	return types.GameMetadata{
+		Proxy:     proxy,
+		Timestamp: timestamp,
+	}
+}
+
+func setupMonitorTest(t *testing.T) (*gameMonitor, *stubGameSource, *stubMonitorMetricer, *mockMetadataCreator) {
+	logger := testlog.Logger(t, log.LvlDebug)
+	source := &stubGameSource{}
+	fetchBlockNum := func(ctx context.Context) (uint64, error) {
+		return 1, nil
+	}
+	fetchBlockHash := func(ctx context.Context, number *big.Int) (common.Hash, error) {
+		return common.Hash{}, nil
+	}
+	metrics := &stubMonitorMetricer{}
+	monitorInterval := time.Duration(100 * time.Millisecond)
+	loader := &mockMetadataLoader{}
+	creator := &mockMetadataCreator{loader: loader}
+	cl := clock.NewAdvancingClock(10 * time.Millisecond)
+	cl.Start()
+	monitor := newGameMonitor(
+		context.Background(),
+		logger,
+		metrics,
+		cl,
+		monitorInterval,
+		source,
+		creator,
+		time.Duration(10*time.Second),
+		fetchBlockNum,
+		fetchBlockHash,
+	)
+	return monitor, source, metrics, creator
+}
+
+type mockMetadataCreator struct {
+	calls  int
+	err    error
+	loader *mockMetadataLoader
+}
+
+func (m *mockMetadataCreator) CreateContract(game types.GameMetadata) (MetadataLoader, error) {
+	m.calls++
+	if m.err != nil {
+		return nil, m.err
+	}
+	return m.loader, nil
+}
+
+type mockMetadataLoader struct {
+	calls  int
+	status types.GameStatus
+	err    error
+}
+
+func (m *mockMetadataLoader) GetGameMetadata(ctx context.Context) (uint64, common.Hash, types.GameStatus, error) {
+	m.calls++
+	if m.err != nil {
+		return 0, common.Hash{}, m.status, m.err
+	}
+	return 0, common.Hash{}, m.status, nil
+}
+
+type stubMonitorMetricer struct {
+	inProgress    int
+	defenderWon   int
+	challengerWon int
+}
+
+func (s *stubMonitorMetricer) RecordGamesStatus(inProgress, defenderWon, challengerWon int) {
+	s.inProgress = inProgress
+	s.defenderWon = defenderWon
+	s.challengerWon = challengerWon
+}
+
+type stubGameSource struct {
+	fetchErr   error
+	calls      int
+	maxSuccess int
+	games      []types.GameMetadata
+}
+
+func (s *stubGameSource) GetGamesAtOrAfter(
+	_ context.Context,
+	_ common.Hash,
+	_ uint64,
+) ([]types.GameMetadata, error) {
+	s.calls++
+	if s.fetchErr != nil {
+		return nil, s.fetchErr
+	}
+	if s.calls > s.maxSuccess && s.maxSuccess != 0 {
+		return nil, mockErr
+	}
+	return s.games, nil
+}

op-dispute-mon/mon/service.go

@@ -4,23 +4,36 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"math/big"
 	"sync/atomic"
 
+	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/ethclient"
 	"github.com/ethereum/go-ethereum/log"
 
+	"github.com/ethereum-optimism/optimism/op-challenger/game/fault/contracts"
+
 	"github.com/ethereum-optimism/optimism/op-dispute-mon/config"
 	"github.com/ethereum-optimism/optimism/op-dispute-mon/metrics"
 	"github.com/ethereum-optimism/optimism/op-dispute-mon/version"
+	"github.com/ethereum-optimism/optimism/op-service/clock"
 	"github.com/ethereum-optimism/optimism/op-service/dial"
 	"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"
+	"github.com/ethereum-optimism/optimism/op-service/sources/batching"
 )
 
 type Service struct {
 	logger  log.Logger
 	metrics metrics.Metricer
+	monitor *gameMonitor
+
+	factoryContract *contracts.DisputeGameFactoryContract
+
+	cl clock.Clock
+
+	metadata *metadataCreator
 
 	l1Client *ethclient.Client
 
@@ -33,6 +46,7 @@ type Service struct {
 // NewService creates a new Service.
 func NewService(ctx context.Context, logger log.Logger, cfg *config.Config) (*Service, error) {
 	s := &Service{
+		cl:      clock.SystemClock,
 		logger:  logger,
 		metrics: metrics.NewMetrics(),
 	}
@@ -54,12 +68,22 @@ func (s *Service) initFromConfig(ctx context.Context, cfg *config.Config) error
 	if err := s.initMetricsServer(&cfg.MetricsConfig); err != nil {
 		return fmt.Errorf("failed to init metrics server: %w", err)
 	}
+	if err := s.initFactoryContract(cfg); err != nil {
+		return fmt.Errorf("failed to create factory contract bindings: %w", err)
+	}
+	s.initMetadataCreator()
+	s.initMonitor(ctx, cfg)
 
 	s.metrics.RecordInfo(version.SimpleWithMeta)
 	s.metrics.RecordUp()
+
 	return nil
 }
 
+func (s *Service) initMetadataCreator() {
+	s.metadata = NewMetadataCreator(s.metrics, batching.NewMultiCaller(s.l1Client.Client(), batching.DefaultBatchSize))
+}
+
 func (s *Service) initL1Client(ctx context.Context, cfg *config.Config) error {
 	l1Client, err := dial.DialEthClientWithTimeout(ctx, dial.DefaultDialTimeout, s.logger, cfg.L1EthRpc)
 	if err != nil {
@@ -104,9 +128,42 @@ func (s *Service) initMetricsServer(cfg *opmetrics.CLIConfig) error {
 	return nil
 }
 
+func (s *Service) initFactoryContract(cfg *config.Config) error {
+	factoryContract, err := contracts.NewDisputeGameFactoryContract(cfg.GameFactoryAddress,
+		batching.NewMultiCaller(s.l1Client.Client(), batching.DefaultBatchSize))
+	if err != nil {
+		return fmt.Errorf("failed to bind the fault dispute game factory contract: %w", err)
+	}
+	s.factoryContract = factoryContract
+	return nil
+}
+
+func (s *Service) initMonitor(ctx context.Context, cfg *config.Config) {
+	blockHashFetcher := func(ctx context.Context, blockNumber *big.Int) (common.Hash, error) {
+		block, err := s.l1Client.BlockByNumber(ctx, blockNumber)
+		if err != nil {
+			return common.Hash{}, fmt.Errorf("failed to fetch block by number: %w", err)
+		}
+		return block.Hash(), nil
+	}
+	s.monitor = newGameMonitor(
+		ctx,
+		s.logger,
+		s.metrics,
+		s.cl,
+		cfg.MonitorInterval,
+		s.factoryContract,
+		s.metadata,
+		cfg.GameWindow,
+		s.l1Client.BlockNumber,
+		blockHashFetcher,
+	)
+}
+
 func (s *Service) Start(ctx context.Context) error {
 	s.logger.Info("starting scheduler")
 	s.logger.Info("starting monitoring")
+	s.monitor.StartMonitoring()
 	s.logger.Info("dispute monitor game service start completed")
 	return nil
 }