op-supervisor: Add Routine to run Maintenence

op-supervisor/supervisor/backend/backend.go

@@ -101,11 +101,14 @@ func (su *SupervisorBackend) Start(ctx context.Context) error {
 	if !su.started.CompareAndSwap(false, true) {
 		return errors.New("already started")
 	}
+	// start chain monitors
 	for _, monitor := range su.chainMonitors {
 		if err := monitor.Start(); err != nil {
 			return fmt.Errorf("failed to start chain monitor: %w", err)
 		}
 	}
+	// start db maintenance loop
+	su.db.StartCrossHeadMaintenance(ctx)
 	return nil
 }
 

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

@@ -1,16 +1,19 @@
 package db
 
 import (
+	"context"
 	"errors"
 	"fmt"
 	"io"
+	"time"
 
 	"github.com/ethereum-optimism/optimism/op-service/eth"
 	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend/db/entrydb"
 	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend/db/heads"
 	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend/db/logs"
 	backendTypes "github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend/types"
 	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/types"
+	"github.com/ethereum/go-ethereum/log"
 )
 
 var (
@@ -59,6 +62,35 @@ func (db *ChainsDB) Resume() error {
 	return nil
 }
 
+// StartCrossHeadMaintenance starts a background process that maintains the cross-heads of the chains
+// for now it does not prevent multiple instances of this process from running
+func (db *ChainsDB) StartCrossHeadMaintenance(ctx context.Context) {
+	go func() {
+		// create three safety checkers, one for each safety level
+		unsafeChecker := NewSafetyChecker(Unsafe, *db)
+		safeChecker := NewSafetyChecker(Safe, *db)
+		finalizedChecker := NewSafetyChecker(Finalized, *db)
+		// run the maintenance loop every 10 seconds for now
+		ticker := time.NewTicker(time.Second * 10)
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			case <-ticker.C:
+				for _, checker := range []SafetyChecker{
+					unsafeChecker,
+					safeChecker,
+					finalizedChecker} {
+					if err := db.UpdateCrossHeads(checker); err != nil {
+						log.Error("failed to update cross-heads", "err", err, "safety", checker.Name())
+						// we should consider exiting if an error is encountered, as the path forward is unclear
+					}
+				}
+			}
+		}
+	}()
+}
+
 // UpdateCrossSafeHeads updates the cross-heads of all chains
 // this is an example of how to use the SafetyChecker to update the cross-heads
 func (db *ChainsDB) UpdateCrossSafeHeads() error {
@@ -117,7 +149,7 @@ func (db *ChainsDB) UpdateCrossHeadsForChain(chainID types.ChainID, checker Safe
 	return nil
 }
 
-// UpdateCrossSafeHeads updates the cross-heads of all chains
+// UpdateCrossHeads updates the cross-heads of all chains
 // based on the provided SafetyChecker. The SafetyChecker is used to determine
 // the safety of each log entry in the database, and the cross-head associated with it.
 func (db *ChainsDB) UpdateCrossHeads(checker SafetyChecker) error {

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

@@ -213,6 +213,10 @@ func (s *stubChecker) LocalHeadForChain(chainID types.ChainID) entrydb.EntryIdx
 	return s.localHeadForChain
 }
 
+func (s *stubChecker) Name() string {
+	return "stubChecker"
+}
+
 func (s *stubChecker) CrossHeadForChain(chainID types.ChainID) entrydb.EntryIdx {
 	return s.crossHeadForChain
 }

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

@@ -20,6 +20,7 @@ type SafetyChecker interface {
 	CrossHeadForChain(chainID types.ChainID) entrydb.EntryIdx
 	Check(chain types.ChainID, blockNum uint64, logIdx uint32, logHash backendTypes.TruncatedHash) bool
 	Update(chain types.ChainID, index entrydb.EntryIdx) heads.OperationFn
+	Name() string
 }
 
 // unsafeChecker is a SafetyChecker that uses the unsafe head as the view into the database
@@ -57,6 +58,19 @@ func NewSafetyChecker(t string, chainsDB ChainsDB) SafetyChecker {
 	}
 }
 
+// Name returns the safety checker type, using the same strings as the constants used in construction
+func (c *unsafeChecker) Name() string {
+	return Unsafe
+}
+
+func (c *safeChecker) Name() string {
+	return Safe
+}
+
+func (c *finalizedChecker) Name() string {
+	return Finalized
+}
+
 // LocalHeadForChain returns the local head for the given chain
 // based on the type of SafetyChecker
 func (c *unsafeChecker) LocalHeadForChain(chainID types.ChainID) entrydb.EntryIdx {