op-dispute-mon: Use game data from previous update cycle if update fails (#12481)

op-dispute-mon/metrics/metrics.go

@@ -183,6 +183,8 @@ type Metricer interface {
 
 	RecordL2Challenges(agreement bool, count int)
 
+	RecordOldestGameUpdateTime(t time.Time)
+
 	caching.Metrics
 	contractMetrics.ContractMetricer
 }
@@ -215,7 +217,8 @@ type Metrics struct {
 	credits                   prometheus.GaugeVec
 	honestWithdrawableAmounts prometheus.GaugeVec
 
-	lastOutputFetch prometheus.Gauge
+	lastOutputFetch      prometheus.Gauge
+	oldestGameUpdateTime prometheus.Gauge
 
 	gamesAgreement             prometheus.GaugeVec
 	latestValidProposalL2Block prometheus.Gauge
@@ -269,6 +272,12 @@ func NewMetrics() *Metrics {
 			Name:      "last_output_fetch",
 			Help:      "Timestamp of the last output fetch",
 		}),
+		oldestGameUpdateTime: factory.NewGauge(prometheus.GaugeOpts{
+			Namespace: Namespace,
+			Name:      "oldest_game_update_time",
+			Help: "Timestamp the least recently updated game " +
+				"or the time of the last update cycle if there were no games in the monitoring window",
+		}),
 		honestActorClaims: *factory.NewGaugeVec(prometheus.GaugeOpts{
 			Namespace: Namespace,
 			Name:      "honest_actor_claims",
@@ -499,6 +508,10 @@ func (m *Metrics) RecordOutputFetchTime(timestamp float64) {
 	m.lastOutputFetch.Set(timestamp)
 }
 
+func (m *Metrics) RecordOldestGameUpdateTime(t time.Time) {
+	m.oldestGameUpdateTime.Set(float64(t.Unix()))
+}
+
 func (m *Metrics) RecordGameAgreement(status GameAgreementStatus, count int) {
 	m.gamesAgreement.WithLabelValues(labelValuesFor(status)...).Set(float64(count))
 }

op-dispute-mon/metrics/noop.go

@@ -36,6 +36,8 @@ func (*NoopMetricsImpl) RecordWithdrawalRequests(_ common.Address, _ bool, _ int
 
 func (*NoopMetricsImpl) RecordOutputFetchTime(_ float64) {}
 
+func (*NoopMetricsImpl) RecordOldestGameUpdateTime(_ time.Time) {}
+
 func (*NoopMetricsImpl) RecordGameAgreement(_ GameAgreementStatus, _ int) {}
 
 func (*NoopMetricsImpl) RecordLatestValidProposalL2Block(_ uint64) {}

op-dispute-mon/mon/extract/extractor.go

@@ -9,9 +9,11 @@ import (
 
 	gameTypes "github.com/ethereum-optimism/optimism/op-challenger/game/types"
 	monTypes "github.com/ethereum-optimism/optimism/op-dispute-mon/mon/types"
+	"github.com/ethereum-optimism/optimism/op-service/clock"
 	"github.com/ethereum-optimism/optimism/op-service/sources/batching/rpcblock"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/log"
+	"golang.org/x/exp/maps"
 )
 
 var (
@@ -29,20 +31,23 @@ type Enricher interface {
 
 type Extractor struct {
 	logger         log.Logger
+	clock          clock.Clock
 	createContract CreateGameCaller
 	fetchGames     FactoryGameFetcher
 	maxConcurrency int
 	enrichers      []Enricher
 	ignoredGames   map[common.Address]bool
+	latestGameData map[common.Address]*monTypes.EnrichedGameData
 }
 
-func NewExtractor(logger log.Logger, creator CreateGameCaller, fetchGames FactoryGameFetcher, ignoredGames []common.Address, maxConcurrency uint, enrichers ...Enricher) *Extractor {
+func NewExtractor(logger log.Logger, cl clock.Clock, creator CreateGameCaller, fetchGames FactoryGameFetcher, ignoredGames []common.Address, maxConcurrency uint, enrichers ...Enricher) *Extractor {
 	ignored := make(map[common.Address]bool)
 	for _, game := range ignoredGames {
 		ignored[game] = true
 	}
 	return &Extractor{
 		logger:         logger,
+		clock:          cl,
 		createContract: creator,
 		fetchGames:     fetchGames,
 		maxConcurrency: int(maxConcurrency),
@@ -61,7 +66,6 @@ func (e *Extractor) Extract(ctx context.Context, blockHash common.Hash, minTimes
 }
 
 func (e *Extractor) enrichGames(ctx context.Context, blockHash common.Hash, games []gameTypes.GameMetadata) ([]*monTypes.EnrichedGameData, int, int) {
-	var enrichedGames []*monTypes.EnrichedGameData
 	var ignored atomic.Int32
 	var failed atomic.Int32
 
@@ -101,8 +105,14 @@ func (e *Extractor) enrichGames(ctx context.Context, blockHash common.Hash, game
 		}()
 	}
 
-	// Push each game into the channel
+	// Create a new store for game data. This ensures any games no longer in the monitoring set are dropped.
+	updatedGameData := make(map[common.Address]*monTypes.EnrichedGameData)
+	// Push each game into the channel and store the latest cached game data as a default if fetching fails
 	for _, game := range games {
+		previousData := e.latestGameData[game.Proxy]
+		if previousData != nil {
+			updatedGameData[game.Proxy] = previousData
+		}
 		gameCh <- game
 	}
 	close(gameCh)
@@ -112,9 +122,10 @@ func (e *Extractor) enrichGames(ctx context.Context, blockHash common.Hash, game
 
 	// Read the results
 	for enrichedGame := range enrichedCh {
-		enrichedGames = append(enrichedGames, enrichedGame)
+		updatedGameData[enrichedGame.Proxy] = enrichedGame
 	}
-	return enrichedGames, int(ignored.Load()), int(failed.Load())
+	e.latestGameData = updatedGameData
+	return maps.Values(updatedGameData), int(ignored.Load()), int(failed.Load())
 }
 
 func (e *Extractor) enrichGame(ctx context.Context, blockHash common.Hash, game gameTypes.GameMetadata) (*monTypes.EnrichedGameData, error) {
@@ -138,6 +149,7 @@ func (e *Extractor) enrichGame(ctx context.Context, blockHash common.Hash, game
 		enrichedClaims[i] = monTypes.EnrichedClaim{Claim: claim}
 	}
 	enrichedGame := &monTypes.EnrichedGameData{
+		LastUpdateTime:        e.clock.Now(),
 		GameMetadata:          game,
 		L1Head:                meta.L1Head,
 		L2BlockNumber:         meta.L2BlockNum,

op-dispute-mon/mon/extract/extractor_test.go

@@ -9,6 +9,7 @@ import (
 
 	"github.com/ethereum-optimism/optimism/op-challenger/game/fault/contracts"
 	monTypes "github.com/ethereum-optimism/optimism/op-dispute-mon/mon/types"
+	"github.com/ethereum-optimism/optimism/op-service/clock"
 	"github.com/ethereum-optimism/optimism/op-service/sources/batching/rpcblock"
 	"github.com/stretchr/testify/require"
 
@@ -26,7 +27,7 @@ var (
 
 func TestExtractor_Extract(t *testing.T) {
 	t.Run("FetchGamesError", func(t *testing.T) {
-		extractor, _, games, _ := setupExtractorTest(t)
+		extractor, _, games, _, _ := setupExtractorTest(t)
 		games.err = errors.New("boom")
 		_, _, _, err := extractor.Extract(context.Background(), common.Hash{}, 0)
 		require.ErrorIs(t, err, games.err)
@@ -34,7 +35,7 @@ func TestExtractor_Extract(t *testing.T) {
 	})
 
 	t.Run("CreateGameErrorLog", func(t *testing.T) {
-		extractor, creator, games, logs := setupExtractorTest(t)
+		extractor, creator, games, logs, _ := setupExtractorTest(t)
 		games.games = []gameTypes.GameMetadata{{}}
 		creator.err = errors.New("boom")
 		enriched, ignored, failed, err := extractor.Extract(context.Background(), common.Hash{}, 0)
@@ -50,7 +51,7 @@ func TestExtractor_Extract(t *testing.T) {
 	})
 
 	t.Run("MetadataFetchErrorLog", func(t *testing.T) {
-		extractor, creator, games, logs := setupExtractorTest(t)
+		extractor, creator, games, logs, _ := setupExtractorTest(t)
 		games.games = []gameTypes.GameMetadata{{}}
 		creator.caller.metadataErr = errors.New("boom")
 		enriched, ignored, failed, err := extractor.Extract(context.Background(), common.Hash{}, 0)
@@ -66,7 +67,7 @@ func TestExtractor_Extract(t *testing.T) {
 	})
 
 	t.Run("ClaimsFetchErrorLog", func(t *testing.T) {
-		extractor, creator, games, logs := setupExtractorTest(t)
+		extractor, creator, games, logs, _ := setupExtractorTest(t)
 		games.games = []gameTypes.GameMetadata{{}}
 		creator.caller.claimsErr = errors.New("boom")
 		enriched, ignored, failed, err := extractor.Extract(context.Background(), common.Hash{}, 0)
@@ -82,7 +83,7 @@ func TestExtractor_Extract(t *testing.T) {
 	})
 
 	t.Run("Success", func(t *testing.T) {
-		extractor, creator, games, _ := setupExtractorTest(t)
+		extractor, creator, games, _, _ := setupExtractorTest(t)
 		games.games = []gameTypes.GameMetadata{{}}
 		enriched, ignored, failed, err := extractor.Extract(context.Background(), common.Hash{}, 0)
 		require.NoError(t, err)
@@ -97,7 +98,7 @@ func TestExtractor_Extract(t *testing.T) {
 
 	t.Run("EnricherFails", func(t *testing.T) {
 		enricher := &mockEnricher{err: errors.New("whoops")}
-		extractor, _, games, logs := setupExtractorTest(t, enricher)
+		extractor, _, games, logs, _ := setupExtractorTest(t, enricher)
 		games.games = []gameTypes.GameMetadata{{}}
 		enriched, ignored, failed, err := extractor.Extract(context.Background(), common.Hash{}, 0)
 		require.NoError(t, err)
@@ -110,7 +111,7 @@ func TestExtractor_Extract(t *testing.T) {
 
 	t.Run("EnricherSuccess", func(t *testing.T) {
 		enricher := &mockEnricher{}
-		extractor, _, games, _ := setupExtractorTest(t, enricher)
+		extractor, _, games, _, _ := setupExtractorTest(t, enricher)
 		games.games = []gameTypes.GameMetadata{{}}
 		enriched, ignored, failed, err := extractor.Extract(context.Background(), common.Hash{}, 0)
 		require.NoError(t, err)
@@ -123,8 +124,8 @@ func TestExtractor_Extract(t *testing.T) {
 	t.Run("MultipleEnrichersMultipleGames", func(t *testing.T) {
 		enricher1 := &mockEnricher{}
 		enricher2 := &mockEnricher{}
-		extractor, _, games, _ := setupExtractorTest(t, enricher1, enricher2)
-		games.games = []gameTypes.GameMetadata{{}, {}}
+		extractor, _, games, _, _ := setupExtractorTest(t, enricher1, enricher2)
+		games.games = []gameTypes.GameMetadata{{Proxy: common.Address{0xaa}}, {Proxy: common.Address{0xbb}}}
 		enriched, ignored, failed, err := extractor.Extract(context.Background(), common.Hash{}, 0)
 		require.NoError(t, err)
 		require.Zero(t, ignored)
@@ -136,7 +137,7 @@ func TestExtractor_Extract(t *testing.T) {
 
 	t.Run("IgnoreGames", func(t *testing.T) {
 		enricher1 := &mockEnricher{}
-		extractor, _, games, logs := setupExtractorTest(t, enricher1)
+		extractor, _, games, logs, _ := setupExtractorTest(t, enricher1)
 		// Two games, one of which is ignored
 		games.games = []gameTypes.GameMetadata{{Proxy: ignoredGames[0]}, {Proxy: common.Address{0xaa}}}
 		enriched, ignored, failed, err := extractor.Extract(context.Background(), common.Hash{}, 0)
@@ -152,6 +153,47 @@ func TestExtractor_Extract(t *testing.T) {
 			testlog.NewMessageFilter("Ignoring game"),
 			testlog.NewAttributesFilter("game", ignoredGames[0].Hex())))
 	})
+
+	t.Run("UseCachedValueOnFailure", func(t *testing.T) {
+		enricher := &mockEnricher{}
+		extractor, _, games, _, cl := setupExtractorTest(t, enricher)
+		gameA := common.Address{0xaa}
+		gameB := common.Address{0xbb}
+		games.games = []gameTypes.GameMetadata{{Proxy: gameA}, {Proxy: gameB}}
+
+		// First fetch succeeds and the results should be cached
+		enriched, ignored, failed, err := extractor.Extract(context.Background(), common.Hash{}, 0)
+		require.NoError(t, err)
+		require.Zero(t, ignored)
+		require.Zero(t, failed)
+		require.Len(t, enriched, 2)
+		require.Equal(t, 2, enricher.calls)
+		firstUpdateTime := cl.Now()
+		require.Equal(t, firstUpdateTime, enriched[0].LastUpdateTime)
+		require.Equal(t, firstUpdateTime, enriched[1].LastUpdateTime)
+
+		cl.AdvanceTime(2 * time.Minute)
+		secondUpdateTime := cl.Now()
+		enricher.action = func(game *monTypes.EnrichedGameData) error {
+			if game.Proxy == gameA {
+				return errors.New("boom")
+			}
+			// Updated games will have a different status
+			game.Status = gameTypes.GameStatusChallengerWon
+			return nil
+		}
+		// Second fetch fails for one of the two games, it's cached value should be used.
+		enriched, ignored, failed, err = extractor.Extract(context.Background(), common.Hash{}, 0)
+		require.NoError(t, err)
+		require.Zero(t, ignored)
+		require.Equal(t, 1, failed)
+		require.Len(t, enriched, 2)
+		require.Equal(t, 4, enricher.calls)
+		require.Equal(t, enriched[0].Status, gameTypes.GameStatusInProgress)    // Uses cached value from game A
+		require.Equal(t, enriched[1].Status, gameTypes.GameStatusChallengerWon) // Updates game B
+		require.Equal(t, firstUpdateTime, enriched[0].LastUpdateTime)
+		require.Equal(t, secondUpdateTime, enriched[1].LastUpdateTime)
+	})
 }
 
 func verifyLogs(t *testing.T, logs *testlog.CapturingHandler, createErr, metadataErr, claimsErr, durationErr int) {
@@ -170,20 +212,22 @@ func verifyLogs(t *testing.T, logs *testlog.CapturingHandler, createErr, metadat
 	require.Len(t, l, durationErr)
 }
 
-func setupExtractorTest(t *testing.T, enrichers ...Enricher) (*Extractor, *mockGameCallerCreator, *mockGameFetcher, *testlog.CapturingHandler) {
+func setupExtractorTest(t *testing.T, enrichers ...Enricher) (*Extractor, *mockGameCallerCreator, *mockGameFetcher, *testlog.CapturingHandler, *clock.DeterministicClock) {
 	logger, capturedLogs := testlog.CaptureLogger(t, log.LvlDebug)
 	games := &mockGameFetcher{}
 	caller := &mockGameCaller{rootClaim: mockRootClaim}
 	creator := &mockGameCallerCreator{caller: caller}
+	cl := clock.NewDeterministicClock(time.Unix(48294294, 58))
 	extractor := NewExtractor(
 		logger,
+		cl,
 		creator.CreateGameCaller,
 		games.FetchGames,
 		ignoredGames,
 		5,
 		enrichers...,
 	)
-	return extractor, creator, games, capturedLogs
+	return extractor, creator, games, capturedLogs, cl
 }
 
 type mockGameFetcher struct {
@@ -311,11 +355,15 @@ func (m *mockGameCaller) IsResolved(_ context.Context, _ rpcblock.Block, claims
 }
 
 type mockEnricher struct {
-	err   error
-	calls int
+	err    error
+	calls  int
+	action func(game *monTypes.EnrichedGameData) error
 }
 
-func (m *mockEnricher) Enrich(_ context.Context, _ rpcblock.Block, _ GameCaller, _ *monTypes.EnrichedGameData) error {
+func (m *mockEnricher) Enrich(_ context.Context, _ rpcblock.Block, _ GameCaller, game *monTypes.EnrichedGameData) error {
 	m.calls++
+	if m.action != nil {
+		return m.action(game)
+	}
 	return m.err
 }

op-dispute-mon/mon/monitor.go

@@ -14,8 +14,6 @@ import (
 )
 
 type ForecastResolution func(games []*types.EnrichedGameData, ignoredCount, failedCount int)
-type Bonds func(games []*types.EnrichedGameData)
-type Resolutions func(games []*types.EnrichedGameData)
 type Monitor func(games []*types.EnrichedGameData)
 type BlockHashFetcher func(ctx context.Context, number *big.Int) (common.Hash, error)
 type BlockNumberFetcher func(ctx context.Context) (uint64, error)
@@ -38,11 +36,7 @@ type gameMonitor struct {
 	monitorInterval time.Duration
 
 	forecast         ForecastResolution
-	bonds            Bonds
-	resolutions      Resolutions
-	claims           Monitor
-	withdrawals      Monitor
-	l2Challenges     Monitor
+	monitors         []Monitor
 	extract          Extract
 	fetchBlockHash   BlockHashFetcher
 	fetchBlockNumber BlockNumberFetcher
@@ -55,16 +49,11 @@ func newGameMonitor(
 	metrics MonitorMetrics,
 	monitorInterval time.Duration,
 	gameWindow time.Duration,
-	forecast ForecastResolution,
-	bonds Bonds,
-	resolutions Resolutions,
-	claims Monitor,
-	withdrawals Monitor,
-	l2Challenges Monitor,
-	extract Extract,
-	fetchBlockNumber BlockNumberFetcher,
 	fetchBlockHash BlockHashFetcher,
-) *gameMonitor {
+	fetchBlockNumber BlockNumberFetcher,
+	extract Extract,
+	forecast ForecastResolution,
+	monitors ...Monitor) *gameMonitor {
 	return &gameMonitor{
 		logger:           logger,
 		clock:            cl,
@@ -74,11 +63,7 @@ func newGameMonitor(
 		monitorInterval:  monitorInterval,
 		gameWindow:       gameWindow,
 		forecast:         forecast,
-		bonds:            bonds,
-		resolutions:      resolutions,
-		claims:           claims,
-		withdrawals:      withdrawals,
-		l2Challenges:     l2Challenges,
+		monitors:         monitors,
 		extract:          extract,
 		fetchBlockNumber: fetchBlockNumber,
 		fetchBlockHash:   fetchBlockHash,
@@ -101,12 +86,10 @@ func (m *gameMonitor) monitorGames() error {
 	if err != nil {
 		return fmt.Errorf("failed to load games: %w", err)
 	}
-	m.resolutions(enrichedGames)
 	m.forecast(enrichedGames, ignored, failed)
-	m.bonds(enrichedGames)
-	m.claims(enrichedGames)
-	m.withdrawals(enrichedGames)
-	m.l2Challenges(enrichedGames)
+	for _, monitor := range m.monitors {
+		monitor(enrichedGames)
+	}
 	timeTaken := m.clock.Since(start)
 	m.metrics.RecordMonitorDuration(timeTaken)
 	m.logger.Info("Completed monitoring update", "blockNumber", blockNumber, "blockHash", blockHash, "duration", timeTaken, "games", len(enrichedGames), "ignored", ignored, "failed", failed)

op-dispute-mon/mon/monitor_test.go

@@ -25,7 +25,7 @@ func TestMonitor_MonitorGames(t *testing.T) {
 	t.Parallel()
 
 	t.Run("FailedFetchBlocknumber", func(t *testing.T) {
-		monitor, _, _, _, _, _, _, _ := setupMonitorTest(t)
+		monitor, _, _, _ := setupMonitorTest(t)
 		boom := errors.New("boom")
 		monitor.fetchBlockNumber = func(ctx context.Context) (uint64, error) {
 			return 0, boom
@@ -35,7 +35,7 @@ func TestMonitor_MonitorGames(t *testing.T) {
 	})
 
 	t.Run("FailedFetchBlockHash", func(t *testing.T) {
-		monitor, _, _, _, _, _, _, _ := setupMonitorTest(t)
+		monitor, _, _, _ := setupMonitorTest(t)
 		boom := errors.New("boom")
 		monitor.fetchBlockHash = func(ctx context.Context, number *big.Int) (common.Hash, error) {
 			return common.Hash{}, boom
@@ -45,29 +45,25 @@ func TestMonitor_MonitorGames(t *testing.T) {
 	})
 
 	t.Run("MonitorsWithNoGames", func(t *testing.T) {
-		monitor, factory, forecast, bonds, withdrawals, resolutions, claims, l2Challenges := setupMonitorTest(t)
+		monitor, factory, forecast, monitors := setupMonitorTest(t)
 		factory.games = []*monTypes.EnrichedGameData{}
 		err := monitor.monitorGames()
 		require.NoError(t, err)
 		require.Equal(t, 1, forecast.calls)
-		require.Equal(t, 1, bonds.calls)
-		require.Equal(t, 1, resolutions.calls)
-		require.Equal(t, 1, claims.calls)
-		require.Equal(t, 1, withdrawals.calls)
-		require.Equal(t, 1, l2Challenges.calls)
+		for _, m := range monitors {
+			require.Equal(t, 1, m.calls)
+		}
 	})
 
 	t.Run("MonitorsMultipleGames", func(t *testing.T) {
-		monitor, factory, forecast, bonds, withdrawals, resolutions, claims, l2Challenges := setupMonitorTest(t)
+		monitor, factory, forecast, monitors := setupMonitorTest(t)
 		factory.games = []*monTypes.EnrichedGameData{{}, {}, {}}
 		err := monitor.monitorGames()
 		require.NoError(t, err)
 		require.Equal(t, 1, forecast.calls)
-		require.Equal(t, 1, bonds.calls)
-		require.Equal(t, 1, resolutions.calls)
-		require.Equal(t, 1, claims.calls)
-		require.Equal(t, 1, withdrawals.calls)
-		require.Equal(t, 1, l2Challenges.calls)
+		for _, m := range monitors {
+			require.Equal(t, 1, m.calls)
+		}
 	})
 }
 
@@ -75,7 +71,7 @@ func TestMonitor_StartMonitoring(t *testing.T) {
 	t.Run("MonitorsGames", func(t *testing.T) {
 		addr1 := common.Address{0xaa}
 		addr2 := common.Address{0xbb}
-		monitor, factory, forecaster, _, _, _, _, _ := setupMonitorTest(t)
+		monitor, factory, forecaster, _ := setupMonitorTest(t)
 		factory.games = []*monTypes.EnrichedGameData{newEnrichedGameData(addr1, 9999), newEnrichedGameData(addr2, 9999)}
 		factory.maxSuccess = len(factory.games) // Only allow two successful fetches
 
@@ -88,7 +84,7 @@ func TestMonitor_StartMonitoring(t *testing.T) {
 	})
 
 	t.Run("FailsToFetchGames", func(t *testing.T) {
-		monitor, factory, forecaster, _, _, _, _, _ := setupMonitorTest(t)
+		monitor, factory, forecaster, _ := setupMonitorTest(t)
 		factory.fetchErr = errors.New("boom")
 
 		monitor.StartMonitoring()
@@ -110,7 +106,7 @@ func newEnrichedGameData(proxy common.Address, timestamp uint64) *monTypes.Enric
 	}
 }
 
-func setupMonitorTest(t *testing.T) (*gameMonitor, *mockExtractor, *mockForecast, *mockBonds, *mockMonitor, *mockResolutionMonitor, *mockMonitor, *mockMonitor) {
+func setupMonitorTest(t *testing.T) (*gameMonitor, *mockExtractor, *mockForecast, []*mockMonitor) {
 	logger := testlog.Logger(t, log.LvlDebug)
 	fetchBlockNum := func(ctx context.Context) (uint64, error) {
 		return 1, nil
@@ -123,37 +119,12 @@ func setupMonitorTest(t *testing.T) (*gameMonitor, *mockExtractor, *mockForecast
 	cl.Start()
 	extractor := &mockExtractor{}
 	forecast := &mockForecast{}
-	bonds := &mockBonds{}
-	resolutions := &mockResolutionMonitor{}
-	claims := &mockMonitor{}
-	withdrawals := &mockMonitor{}
-	l2Challenges := &mockMonitor{}
-	monitor := newGameMonitor(
-		context.Background(),
-		logger,
-		cl,
-		metrics.NoopMetrics,
-		monitorInterval,
-		10*time.Second,
-		forecast.Forecast,
-		bonds.CheckBonds,
-		resolutions.CheckResolutions,
-		claims.Check,
-		withdrawals.Check,
-		l2Challenges.Check,
-		extractor.Extract,
-		fetchBlockNum,
-		fetchBlockHash,
-	)
-	return monitor, extractor, forecast, bonds, withdrawals, resolutions, claims, l2Challenges
-}
-
-type mockResolutionMonitor struct {
-	calls int
-}
-
-func (m *mockResolutionMonitor) CheckResolutions(games []*monTypes.EnrichedGameData) {
-	m.calls++
+	monitor1 := &mockMonitor{}
+	monitor2 := &mockMonitor{}
+	monitor3 := &mockMonitor{}
+	monitor := newGameMonitor(context.Background(), logger, cl, metrics.NoopMetrics, monitorInterval, 10*time.Second, fetchBlockHash, fetchBlockNum,
+		extractor.Extract, forecast.Forecast, monitor1.Check, monitor2.Check, monitor3.Check)
+	return monitor, extractor, forecast, []*mockMonitor{monitor1, monitor2, monitor3}
 }
 
 type mockMonitor struct {
@@ -172,14 +143,6 @@ func (m *mockForecast) Forecast(_ []*monTypes.EnrichedGameData, _, _ int) {
 	m.calls++
 }
 
-type mockBonds struct {
-	calls int
-}
-
-func (m *mockBonds) CheckBonds(_ []*monTypes.EnrichedGameData) {
-	m.calls++
-}
-
 type mockExtractor struct {
 	fetchErr     error
 	calls        int

op-dispute-mon/mon/service.go

@@ -126,6 +126,7 @@ func (s *Service) initGameCallerCreator() {
 func (s *Service) initExtractor(cfg *config.Config) {
 	s.extractor = extract.NewExtractor(
 		s.logger,
+		s.cl,
 		s.game.CreateContract,
 		s.factoryContract.GetGamesAtOrAfter,
 		cfg.IgnoredGames,
@@ -217,23 +218,17 @@ func (s *Service) initMonitor(ctx context.Context, cfg *config.Config) {
 		return block.Hash(), nil
 	}
 	l2ChallengesMonitor := NewL2ChallengesMonitor(s.logger, s.metrics)
-	s.monitor = newGameMonitor(
-		ctx,
-		s.logger,
-		s.cl,
-		s.metrics,
-		cfg.MonitorInterval,
-		cfg.GameWindow,
+	updateTimeMonitor := NewUpdateTimeMonitor(s.cl, s.metrics)
+	s.monitor = newGameMonitor(ctx, s.logger, s.cl, s.metrics, cfg.MonitorInterval, cfg.GameWindow, blockHashFetcher,
+		s.l1Client.BlockNumber,
+		s.extractor.Extract,
 		s.forecast.Forecast,
 		s.bonds.CheckBonds,
 		s.resolutions.CheckResolutions,
 		s.claims.CheckClaims,
 		s.withdrawals.CheckWithdrawals,
 		l2ChallengesMonitor.CheckL2Challenges,
-		s.extractor.Extract,
-		s.l1Client.BlockNumber,
-		blockHashFetcher,
-	)
+		updateTimeMonitor.CheckUpdateTimes)
 }
 
 func (s *Service) Start(ctx context.Context) error {

op-dispute-mon/mon/types/types.go

@@ -18,6 +18,7 @@ type EnrichedClaim struct {
 
 type EnrichedGameData struct {
 	types.GameMetadata
+	LastUpdateTime        time.Time
 	L1Head                common.Hash
 	L1HeadNum             uint64
 	L2BlockNumber         uint64

op-dispute-mon/mon/update_times.go

+package mon
+
+import (
+	"time"
+
+	"github.com/ethereum-optimism/optimism/op-dispute-mon/mon/types"
+	"github.com/ethereum-optimism/optimism/op-service/clock"
+)
+
+type UpdateTimeMetrics interface {
+	RecordOldestGameUpdateTime(t time.Time)
+}
+
+type UpdateTimeMonitor struct {
+	metrics UpdateTimeMetrics
+	clock   clock.Clock
+}
+
+func NewUpdateTimeMonitor(cl clock.Clock, metrics UpdateTimeMetrics) *UpdateTimeMonitor {
+	return &UpdateTimeMonitor{clock: cl, metrics: metrics}
+}
+
+func (m *UpdateTimeMonitor) CheckUpdateTimes(games []*types.EnrichedGameData) {
+	// Report the current time if there are no games
+	// Otherwise the last update time would drop to 0 when there are no games, making it appear there were errors
+	earliest := m.clock.Now()
+
+	for _, game := range games {
+		if game.LastUpdateTime.Before(earliest) {
+			earliest = game.LastUpdateTime
+		}
+	}
+	m.metrics.RecordOldestGameUpdateTime(earliest)
+}

op-dispute-mon/mon/update_times_test.go

+package mon
+
+import (
+	"testing"
+	"time"
+
+	"github.com/ethereum-optimism/optimism/op-dispute-mon/mon/types"
+	"github.com/ethereum-optimism/optimism/op-service/clock"
+	"github.com/stretchr/testify/require"
+)
+
+func TestUpdateTimeMonitor_NoGames(t *testing.T) {
+	m := &mockUpdateTimeMetrics{}
+	cl := clock.NewDeterministicClock(time.UnixMilli(45892))
+	monitor := NewUpdateTimeMonitor(cl, m)
+	monitor.CheckUpdateTimes(nil)
+	require.Equal(t, cl.Now(), m.oldestUpdateTime)
+
+	cl.AdvanceTime(time.Minute)
+	monitor.CheckUpdateTimes([]*types.EnrichedGameData{})
+	require.Equal(t, cl.Now(), m.oldestUpdateTime)
+}
+
+func TestUpdateTimeMonitor_ReportsOldestUpdateTime(t *testing.T) {
+	m := &mockUpdateTimeMetrics{}
+	cl := clock.NewDeterministicClock(time.UnixMilli(45892))
+	monitor := NewUpdateTimeMonitor(cl, m)
+	monitor.CheckUpdateTimes([]*types.EnrichedGameData{
+		{LastUpdateTime: time.UnixMilli(4)},
+		{LastUpdateTime: time.UnixMilli(3)},
+		{LastUpdateTime: time.UnixMilli(7)},
+		{LastUpdateTime: time.UnixMilli(9)},
+	})
+	require.Equal(t, time.UnixMilli(3), m.oldestUpdateTime)
+}
+
+type mockUpdateTimeMetrics struct {
+	oldestUpdateTime time.Time
+}
+
+func (m *mockUpdateTimeMetrics) RecordOldestGameUpdateTime(t time.Time) {
+	m.oldestUpdateTime = t
+}