interop: fromda DB (#12436)

* op-supervisor: cleanup, refactor to take local-safe info from op-node

* interop: draft fromda DB

* op-supervisor: fromda DB fixes and tests

* fix test warnings

* add extra check ; remove LatestDerived, LatestDerivedFrom

---------
Co-authored-by: axelKingsley <axel.kingsley@gmail.com>

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

@@ -9,7 +9,14 @@ import (
 	"github.com/ethereum/go-ethereum/log"
 )
 
-const EntrySize = 34
+type EntryStore[T EntryType, E Entry[T]] interface {
+	Size() int64
+	LastEntryIdx() EntryIdx
+	Read(idx EntryIdx) (E, error)
+	Append(entries ...E) error
+	Truncate(idx EntryIdx) error
+	Close() error
+}
 
 type EntryIdx int64
 
@@ -18,10 +25,18 @@ type EntryType interface {
 	~uint8
 }
 
-type Entry[T EntryType] [EntrySize]byte
+type Entry[T EntryType] interface {
+	Type() T
+	comparable
+}
 
-func (entry Entry[T]) Type() T {
-	return T(entry[0])
+// Binary is the binary interface to encode/decode/size entries.
+// This should be a zero-cost abstraction, and is bundled as interface for the EntryDB
+// to have generic access to this functionality without const-generics for array size in Go.
+type Binary[T EntryType, E Entry[T]] interface {
+	Append(dest []byte, e *E) []byte
+	ReadAt(dest *E, r io.ReaderAt, at int64) (n int, err error)
+	EntrySize() int
 }
 
 // dataAccess defines a minimal API required to manipulate the actual stored data.
@@ -33,10 +48,12 @@ type dataAccess interface {
 	Truncate(size int64) error
 }
 
-type EntryDB[T EntryType] struct {
+type EntryDB[T EntryType, E Entry[T], B Binary[T, E]] struct {
 	data         dataAccess
 	lastEntryIdx EntryIdx
 
+	b B
+
 	cleanupFailedWrite bool
 }
 
@@ -45,7 +62,7 @@ type EntryDB[T EntryType] struct {
 // If the file exists it will be used as the existing data.
 // Returns ErrRecoveryRequired if the existing file is not a valid entry db. A EntryDB is still returned but all
 // operations will return ErrRecoveryRequired until the Recover method is called.
-func NewEntryDB[T EntryType](logger log.Logger, path string) (*EntryDB[T], error) {
+func NewEntryDB[T EntryType, E Entry[T], B Binary[T, E]](logger log.Logger, path string) (*EntryDB[T, E, B], error) {
 	logger.Info("Opening entry database", "path", path)
 	file, err := os.OpenFile(path, os.O_RDWR|os.O_CREATE|os.O_APPEND, 0o644)
 	if err != nil {
@@ -55,13 +72,14 @@ func NewEntryDB[T EntryType](logger log.Logger, path string) (*EntryDB[T], error
 	if err != nil {
 		return nil, fmt.Errorf("failed to stat database at %v: %w", path, err)
 	}
-	size := info.Size() / EntrySize
-	db := &EntryDB[T]{
+	var b B
+	size := info.Size() / int64(b.EntrySize())
+	db := &EntryDB[T, E, B]{
 		data:         file,
 		lastEntryIdx: EntryIdx(size - 1),
 	}
-	if size*EntrySize != info.Size() {
-		logger.Warn("File size is not a multiple of entry size. Truncating to last complete entry", "fileSize", size, "entrySize", EntrySize)
+	if size*int64(b.EntrySize()) != info.Size() {
+		logger.Warn("File size is not a multiple of entry size. Truncating to last complete entry", "fileSize", size, "entrySize", b.EntrySize())
 		if err := db.recover(); err != nil {
 			return nil, fmt.Errorf("failed to recover database at %v: %w", path, err)
 		}
@@ -69,24 +87,26 @@ func NewEntryDB[T EntryType](logger log.Logger, path string) (*EntryDB[T], error
 	return db, nil
 }
 
-func (e *EntryDB[T]) Size() int64 {
+func (e *EntryDB[T, E, B]) Size() int64 {
 	return int64(e.lastEntryIdx) + 1
 }
 
-func (e *EntryDB[T]) LastEntryIdx() EntryIdx {
+// LastEntryIdx returns the index of the last entry in the DB.
+// This returns -1 if the DB is empty.
+func (e *EntryDB[T, E, B]) LastEntryIdx() EntryIdx {
 	return e.lastEntryIdx
 }
 
 // Read an entry from the database by index. Returns io.EOF iff idx is after the last entry.
-func (e *EntryDB[T]) Read(idx EntryIdx) (Entry[T], error) {
+func (e *EntryDB[T, E, B]) Read(idx EntryIdx) (E, error) {
+	var out E
 	if idx > e.lastEntryIdx {
-		return Entry[T]{}, io.EOF
+		return out, io.EOF
 	}
-	var out Entry[T]
-	read, err := e.data.ReadAt(out[:], int64(idx)*EntrySize)
+	read, err := e.b.ReadAt(&out, e.data, int64(idx)*int64(e.b.EntrySize()))
 	// Ignore io.EOF if we read the entire last entry as ReadAt may return io.EOF or nil when it reads the last byte
-	if err != nil && !(errors.Is(err, io.EOF) && read == EntrySize) {
-		return Entry[T]{}, fmt.Errorf("failed to read entry %v: %w", idx, err)
+	if err != nil && !(errors.Is(err, io.EOF) && read == e.b.EntrySize()) {
+		return out, fmt.Errorf("failed to read entry %v: %w", idx, err)
 	}
 	return out, nil
 }
@@ -95,16 +115,16 @@ func (e *EntryDB[T]) Read(idx EntryIdx) (Entry[T], error) {
 // The entries are combined in memory and passed to a single Write invocation.
 // If the write fails, it will attempt to truncate any partially written data.
 // Subsequent writes to this instance will fail until partially written data is truncated.
-func (e *EntryDB[T]) Append(entries ...Entry[T]) error {
+func (e *EntryDB[T, E, B]) Append(entries ...E) error {
 	if e.cleanupFailedWrite {
 		// Try to rollback partially written data from a previous Append
 		if truncateErr := e.Truncate(e.lastEntryIdx); truncateErr != nil {
 			return fmt.Errorf("failed to recover from previous write error: %w", truncateErr)
 		}
 	}
-	data := make([]byte, 0, len(entries)*EntrySize)
-	for _, entry := range entries {
-		data = append(data, entry[:]...)
+	data := make([]byte, 0, len(entries)*e.b.EntrySize())
+	for i := range entries {
+		data = e.b.Append(data, &entries[i])
 	}
 	if n, err := e.data.Write(data); err != nil {
 		if n == 0 {
@@ -125,8 +145,8 @@ func (e *EntryDB[T]) Append(entries ...Entry[T]) error {
 }
 
 // Truncate the database so that the last retained entry is idx. Any entries after idx are deleted.
-func (e *EntryDB[T]) Truncate(idx EntryIdx) error {
-	if err := e.data.Truncate((int64(idx) + 1) * EntrySize); err != nil {
+func (e *EntryDB[T, E, B]) Truncate(idx EntryIdx) error {
+	if err := e.data.Truncate((int64(idx) + 1) * int64(e.b.EntrySize())); err != nil {
 		return fmt.Errorf("failed to truncate to entry %v: %w", idx, err)
 	}
 	// Update the lastEntryIdx cache
@@ -136,13 +156,13 @@ func (e *EntryDB[T]) Truncate(idx EntryIdx) error {
 }
 
 // recover an invalid database by truncating back to the last complete event.
-func (e *EntryDB[T]) recover() error {
-	if err := e.data.Truncate((e.Size()) * EntrySize); err != nil {
+func (e *EntryDB[T, E, B]) recover() error {
+	if err := e.data.Truncate(e.Size() * int64(e.b.EntrySize())); err != nil {
 		return fmt.Errorf("failed to truncate trailing partial entries: %w", err)
 	}
 	return nil
 }
 
-func (e *EntryDB[T]) Close() error {
+func (e *EntryDB[T, E, B]) Close() error {
 	return e.data.Close()
 }

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

@@ -9,9 +9,11 @@ import (
 	"path/filepath"
 	"testing"
 
-	"github.com/ethereum-optimism/optimism/op-service/testlog"
-	"github.com/ethereum/go-ethereum/log"
 	"github.com/stretchr/testify/require"
+
+	"github.com/ethereum/go-ethereum/log"
+
+	"github.com/ethereum-optimism/optimism/op-service/testlog"
 )
 
 type TestEntryType uint8
@@ -20,7 +22,31 @@ func (typ TestEntryType) String() string {
 	return fmt.Sprintf("%d", uint8(typ))
 }
 
-type TestEntry = Entry[TestEntryType]
+const TestEntrySize = 34
+
+type TestEntry [TestEntrySize]byte
+
+func (t TestEntry) Type() TestEntryType {
+	return TestEntryType(t[0])
+}
+
+type TestEntryBinary struct{}
+
+func (TestEntryBinary) Append(dest []byte, e *TestEntry) []byte {
+	return append(dest, e[:]...)
+}
+
+func (TestEntryBinary) ReadAt(dest *TestEntry, r io.ReaderAt, at int64) (n int, err error) {
+	return r.ReadAt(dest[:], at)
+}
+
+func (TestEntryBinary) EntrySize() int {
+	return TestEntrySize
+}
+
+var _ Binary[TestEntryType, TestEntry] = TestEntryBinary{}
+
+type TestEntryDB = EntryDB[TestEntryType, TestEntry, TestEntryBinary]
 
 func TestReadWrite(t *testing.T) {
 	t.Run("BasicReadWrite", func(t *testing.T) {
@@ -120,10 +146,10 @@ func TestTruncateTrailingPartialEntries(t *testing.T) {
 	entry2 := createEntry(2)
 	invalidData := make([]byte, len(entry1)+len(entry2)+4)
 	copy(invalidData, entry1[:])
-	copy(invalidData[EntrySize:], entry2[:])
+	copy(invalidData[TestEntrySize:], entry2[:])
 	invalidData[len(invalidData)-1] = 3 // Some invalid trailing data
 	require.NoError(t, os.WriteFile(file, invalidData, 0o644))
-	db, err := NewEntryDB[TestEntryType](logger, file)
+	db, err := NewEntryDB[TestEntryType, TestEntry, TestEntryBinary](logger, file)
 	require.NoError(t, err)
 	defer db.Close()
 
@@ -131,7 +157,7 @@ func TestTruncateTrailingPartialEntries(t *testing.T) {
 	require.EqualValues(t, 2, db.Size())
 	stat, err := os.Stat(file)
 	require.NoError(t, err)
-	require.EqualValues(t, 2*EntrySize, stat.Size())
+	require.EqualValues(t, 2*TestEntrySize, stat.Size())
 }
 
 func TestWriteErrors(t *testing.T) {
@@ -162,7 +188,7 @@ func TestWriteErrors(t *testing.T) {
 	t.Run("PartialWriteAndTruncateFails", func(t *testing.T) {
 		db, stubData := createEntryDBWithStubData()
 		stubData.writeErr = expectedErr
-		stubData.writeErrAfterBytes = EntrySize + 2
+		stubData.writeErrAfterBytes = TestEntrySize + 2
 		stubData.truncateErr = errors.New("boom")
 		err := db.Append(createEntry(1), createEntry(2))
 		require.ErrorIs(t, err, expectedErr)
@@ -186,19 +212,19 @@ func TestWriteErrors(t *testing.T) {
 	})
 }
 
-func requireRead(t *testing.T, db *EntryDB[TestEntryType], idx EntryIdx, expected TestEntry) {
+func requireRead(t *testing.T, db *TestEntryDB, idx EntryIdx, expected TestEntry) {
 	actual, err := db.Read(idx)
 	require.NoError(t, err)
 	require.Equal(t, expected, actual)
 }
 
 func createEntry(i byte) TestEntry {
-	return TestEntry(bytes.Repeat([]byte{i}, EntrySize))
+	return TestEntry(bytes.Repeat([]byte{i}, TestEntrySize))
 }
 
-func createEntryDB(t *testing.T) *EntryDB[TestEntryType] {
+func createEntryDB(t *testing.T) *TestEntryDB {
 	logger := testlog.Logger(t, log.LvlInfo)
-	db, err := NewEntryDB[TestEntryType](logger, filepath.Join(t.TempDir(), "entries.db"))
+	db, err := NewEntryDB[TestEntryType, TestEntry, TestEntryBinary](logger, filepath.Join(t.TempDir(), "entries.db"))
 	require.NoError(t, err)
 	t.Cleanup(func() {
 		require.NoError(t, db.Close())
@@ -206,9 +232,9 @@ func createEntryDB(t *testing.T) *EntryDB[TestEntryType] {
 	return db
 }
 
-func createEntryDBWithStubData() (*EntryDB[TestEntryType], *stubDataAccess) {
+func createEntryDBWithStubData() (*TestEntryDB, *stubDataAccess) {
 	stubData := &stubDataAccess{}
-	db := &EntryDB[TestEntryType]{data: stubData, lastEntryIdx: -1}
+	db := &EntryDB[TestEntryType, TestEntry, TestEntryBinary]{data: stubData, lastEntryIdx: -1}
 	return db, stubData
 }
 

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

+package entrydb
+
+import (
+	"io"
+)
+
+type MemEntryStore[T EntryType, E Entry[T]] struct {
+	entries []E
+}
+
+func (s *MemEntryStore[T, E]) Size() int64 {
+	return int64(len(s.entries))
+}
+
+func (s *MemEntryStore[T, E]) LastEntryIdx() EntryIdx {
+	return EntryIdx(s.Size() - 1)
+}
+
+func (s *MemEntryStore[T, E]) Read(idx EntryIdx) (E, error) {
+	if idx < EntryIdx(len(s.entries)) {
+		return s.entries[idx], nil
+	}
+	var out E
+	return out, io.EOF
+}
+
+func (s *MemEntryStore[T, E]) Append(entries ...E) error {
+	s.entries = append(s.entries, entries...)
+	return nil
+}
+
+func (s *MemEntryStore[T, E]) Truncate(idx EntryIdx) error {
+	s.entries = s.entries[:min(s.Size()-1, int64(idx+1))]
+	return nil
+}
+
+func (s *MemEntryStore[T, E]) Close() error {
+	return nil
+}

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

+package fromda
+
+import (
+	"cmp"
+	"fmt"
+	"sort"
+	"sync"
+
+	"github.com/ethereum/go-ethereum/log"
+
+	"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/types"
+)
+
+type Metrics interface {
+	RecordDBDerivedEntryCount(count int64)
+}
+
+type EntryStore interface {
+	Size() int64
+	LastEntryIdx() entrydb.EntryIdx
+	Read(idx entrydb.EntryIdx) (Entry, error)
+	Append(entries ...Entry) error
+	Truncate(idx entrydb.EntryIdx) error
+	Close() error
+}
+
+// DB implements an append only database for log data and cross-chain dependencies.
+// Each entry is fixed size, and denotes an increment in L1 (derived-from) and/or L2 (derived) block.
+// Data is an append-only log, that can be binary searched for any necessary derivation-link data.
+type DB struct {
+	log    log.Logger
+	m      Metrics
+	store  EntryStore
+	rwLock sync.RWMutex
+}
+
+func NewFromFile(logger log.Logger, m Metrics, path string) (*DB, error) {
+	store, err := entrydb.NewEntryDB[EntryType, Entry, EntryBinary](logger, path)
+	if err != nil {
+		return nil, fmt.Errorf("failed to open DB: %w", err)
+	}
+	return NewFromEntryStore(logger, m, store)
+}
+
+func NewFromEntryStore(logger log.Logger, m Metrics, store EntryStore) (*DB, error) {
+	db := &DB{
+		log:   logger,
+		m:     m,
+		store: store,
+	}
+	db.m.RecordDBDerivedEntryCount(db.store.Size())
+	return db, nil
+}
+
+// Rewind to the last entry that was derived from a L1 block with the given block number.
+func (db *DB) Rewind(derivedFrom uint64) error {
+	index, _, err := db.lastDerivedAt(derivedFrom)
+	if err != nil {
+		return fmt.Errorf("failed to find point to rewind to: %w", err)
+	}
+	err = db.store.Truncate(index)
+	if err != nil {
+		return err
+	}
+	db.m.RecordDBDerivedEntryCount(int64(index) + 1)
+	return nil
+}
+
+// Latest returns the last known values:
+// derivedFrom: the L1 block that the L2 block is safe for (not necessarily the first, multiple L2 blocks may be derived from the same L1 block).
+// derived: the L2 block that was derived (not necessarily the first, the L1 block may have been empty and repeated the last safe L2 block).
+func (db *DB) Latest() (derivedFrom types.BlockSeal, derived types.BlockSeal, err error) {
+	db.rwLock.Lock()
+	defer db.rwLock.Unlock()
+	return db.latest()
+}
+
+// latest is like Latest, but without lock, for internal use.
+func (db *DB) latest() (derivedFrom types.BlockSeal, derived types.BlockSeal, err error) {
+	lastIndex := db.store.LastEntryIdx()
+	if lastIndex < 0 {
+		return types.BlockSeal{}, types.BlockSeal{}, entrydb.ErrFuture
+	}
+	last, err := db.readAt(lastIndex)
+	if err != nil {
+		return types.BlockSeal{}, types.BlockSeal{}, fmt.Errorf("failed to read last derivation data: %w", err)
+	}
+	return last.derivedFrom, last.derived, nil
+}
+
+// LastDerivedAt returns the last L2 block derived from the given L1 block.
+func (db *DB) LastDerivedAt(derivedFrom eth.BlockID) (derived types.BlockSeal, err error) {
+	db.rwLock.RLock()
+	defer db.rwLock.RUnlock()
+	_, link, err := db.lastDerivedAt(derivedFrom.Number)
+	if err != nil {
+		return types.BlockSeal{}, err
+	}
+	if link.derivedFrom.ID() != derivedFrom {
+		return types.BlockSeal{}, fmt.Errorf("searched for last derived-from %s but found %s: %w",
+			derivedFrom, link.derivedFrom, entrydb.ErrConflict)
+	}
+	return link.derived, nil
+}
+
+// DerivedFrom determines where a L2 block was first derived from.
+// (a L2 block may repeat if the following L1 blocks are empty and don't produce additional L2 blocks)
+func (db *DB) DerivedFrom(derived eth.BlockID) (derivedFrom types.BlockSeal, err error) {
+	db.rwLock.RLock()
+	defer db.rwLock.RUnlock()
+	_, link, err := db.firstDerivedFrom(derived.Number)
+	if err != nil {
+		return types.BlockSeal{}, err
+	}
+	if link.derived.ID() != derived {
+		return types.BlockSeal{}, fmt.Errorf("searched for first derived %s but found %s: %w",
+			derived, link.derived, entrydb.ErrConflict)
+	}
+	return link.derivedFrom, nil
+}
+
+func (db *DB) firstDerivedFrom(derived uint64) (entrydb.EntryIdx, LinkEntry, error) {
+	return db.find(false, func(link LinkEntry) int {
+		return cmp.Compare(link.derived.Number, derived)
+	})
+}
+
+func (db *DB) lastDerivedAt(derivedFrom uint64) (entrydb.EntryIdx, LinkEntry, error) {
+	// Reverse: prioritize the last entry.
+	return db.find(true, func(link LinkEntry) int {
+		return cmp.Compare(derivedFrom, link.derivedFrom.Number)
+	})
+}
+
+// find finds the first entry for which cmpFn(link) returns 0.
+// The cmpFn entries to the left should return -1, entries to the right 1.
+// If reverse, the cmpFn should be flipped too, and the last entry for which cmpFn(link) is 0 will be found.
+func (db *DB) find(reverse bool, cmpFn func(link LinkEntry) int) (entrydb.EntryIdx, LinkEntry, error) {
+	n := db.store.Size()
+	if n == 0 {
+		return -1, LinkEntry{}, entrydb.ErrFuture
+	}
+	var searchErr error
+	// binary-search for the smallest index i for which cmp(i) >= 0
+	result := sort.Search(int(n), func(i int) bool {
+		at := entrydb.EntryIdx(i)
+		if reverse {
+			at = entrydb.EntryIdx(n) - 1 - at
+		}
+		entry, err := db.readAt(at)
+		if err != nil {
+			searchErr = err
+			return false
+		}
+		return cmpFn(entry) >= 0
+	})
+	if searchErr != nil {
+		return -1, LinkEntry{}, fmt.Errorf("failed to search: %w", searchErr)
+	}
+	if result == int(n) {
+		if reverse {
+			return -1, LinkEntry{}, fmt.Errorf("no entry found: %w", entrydb.ErrSkipped)
+		} else {
+			return -1, LinkEntry{}, fmt.Errorf("no entry found: %w", entrydb.ErrFuture)
+		}
+	}
+	if reverse {
+		result = int(n) - 1 - result
+	}
+	link, err := db.readAt(entrydb.EntryIdx(result))
+	if err != nil {
+		return -1, LinkEntry{}, fmt.Errorf("failed to read final result entry %d: %w", result, err)
+	}
+	if cmpFn(link) != 0 {
+		if reverse {
+			return -1, LinkEntry{}, fmt.Errorf("lowest entry %s is too high: %w", link, entrydb.ErrFuture)
+		} else {
+			return -1, LinkEntry{}, fmt.Errorf("lowest entry %s is too high: %w", link, entrydb.ErrSkipped)
+		}
+	}
+	if cmpFn(link) != 0 {
+		// Search should have returned lowest entry >= the target.
+		// And we already checked it's not > the target
+		panic(fmt.Errorf("invalid search result %s, did not match equality check", link))
+	}
+	return entrydb.EntryIdx(result), link, nil
+}
+
+func (db *DB) readAt(i entrydb.EntryIdx) (LinkEntry, error) {
+	entry, err := db.store.Read(i)
+	if err != nil {
+		return LinkEntry{}, err
+	}
+	var out LinkEntry
+	err = out.decode(entry)
+	return out, err
+}
+
+func (db *DB) Close() error {
+	db.rwLock.Lock()
+	defer db.rwLock.Unlock()
+	return db.store.Close()
+}

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

+package fromda
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+type statInvariant func(stat os.FileInfo, m *stubMetrics) error
+type linkInvariant func(prev, current LinkEntry) error
+
+// checkDBInvariants reads the database log directly and asserts a set of invariants on the data.
+func checkDBInvariants(t *testing.T, dbPath string, m *stubMetrics) {
+	stat, err := os.Stat(dbPath)
+	require.NoError(t, err)
+
+	statInvariants := []statInvariant{
+		invariantFileSizeMultipleOfEntrySize,
+		invariantFileSizeMatchesEntryCountMetric,
+	}
+	for _, invariant := range statInvariants {
+		require.NoError(t, invariant(stat, m))
+	}
+
+	// Read all entries as binary blobs
+	file, err := os.OpenFile(dbPath, os.O_RDONLY, 0o644)
+	require.NoError(t, err)
+	entries := make([]Entry, stat.Size()/EntrySize)
+	for i := range entries {
+		n, err := io.ReadFull(file, entries[i][:])
+		require.NoErrorf(t, err, "failed to read entry %v", i)
+		require.EqualValuesf(t, EntrySize, n, "read wrong length for entry %v", i)
+	}
+	var links []LinkEntry
+	for i, e := range entries {
+		var v LinkEntry
+		require.NoError(t, v.decode(e), "failed to decode entry %d", i)
+		links = append(links, v)
+	}
+
+	linkInvariants := []linkInvariant{
+		invariantDerivedTimestamp,
+		invariantDerivedFromTimestamp,
+		invariantNumberIncrement,
+	}
+	for i, link := range links {
+		if i == 0 {
+			continue
+		}
+		for _, invariant := range linkInvariants {
+			err := invariant(links[i-1], link)
+			if err != nil {
+				require.NoErrorf(t, err, "Invariant breached: \n%v", fmtEntries(entries))
+			}
+		}
+	}
+}
+
+func fmtEntries(entries []Entry) string {
+	out := ""
+	for i, entry := range entries {
+		out += fmt.Sprintf("%v: %x\n", i, entry)
+	}
+	return out
+}
+
+func invariantFileSizeMultipleOfEntrySize(stat os.FileInfo, _ *stubMetrics) error {
+	size := stat.Size()
+	if size%EntrySize != 0 {
+		return fmt.Errorf("expected file size to be a multiple of entry size (%v) but was %v", EntrySize, size)
+	}
+	return nil
+}
+
+func invariantFileSizeMatchesEntryCountMetric(stat os.FileInfo, m *stubMetrics) error {
+	size := stat.Size()
+	if m.DBDerivedEntryCount*EntrySize != size {
+		return fmt.Errorf("expected file size to be entryCount (%v) * entrySize (%v) = %v but was %v", m.DBDerivedEntryCount, EntrySize, m.DBDerivedEntryCount*EntrySize, size)
+	}
+	return nil
+}
+
+func invariantDerivedTimestamp(prev, current LinkEntry) error {
+	if current.derived.Timestamp < prev.derived.Timestamp {
+		return fmt.Errorf("derived timestamp must be >=, current: %s, prev: %s", current.derived, prev.derived)
+	}
+	return nil
+}
+
+func invariantNumberIncrement(prev, current LinkEntry) error {
+	// derived stays the same if the new L1 block is empty.
+	derivedSame := current.derived.Number == prev.derived.Number
+	// derivedFrom stays the same if this L2 block is derived from the same L1 block as the last L2 block
+	derivedFromSame := current.derivedFrom.Number == prev.derivedFrom.Number
+	// At least one of the two must increment, otherwise we are just repeating data in the DB.
+	if derivedSame && derivedFromSame {
+		return fmt.Errorf("expected at least either derivedFrom or derived to increment, but both have same number")
+	}
+	derivedIncrement := current.derived.Number == prev.derived.Number+1
+	derivedFromIncrement := current.derivedFrom.Number == prev.derivedFrom.Number+1
+	if !(derivedSame || derivedIncrement) {
+		return fmt.Errorf("expected derived to either stay the same or increment, got prev %s current %s", prev.derived, current.derived)
+	}
+	if !(derivedFromSame || derivedFromIncrement) {
+		return fmt.Errorf("expected derivedFrom to either stay the same or increment, got prev %s current %s", prev.derivedFrom, current.derivedFrom)
+	}
+	return nil
+}
+
+func invariantDerivedFromTimestamp(prev, current LinkEntry) error {
+	if current.derivedFrom.Timestamp < prev.derivedFrom.Timestamp {
+		return fmt.Errorf("derivedFrom timestamp must be >=, current: %s, prev: %s", current.derivedFrom, prev.derivedFrom)
+	}
+	return nil
+}

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

+package fromda
+
+import (
+	"fmt"
+	"io/fs"
+	"math/rand" // nosemgrep
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/log"
+
+	"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/db/entrydb"
+	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/types"
+)
+
+type stubMetrics struct {
+	DBDerivedEntryCount int64
+}
+
+func (s *stubMetrics) RecordDBDerivedEntryCount(count int64) {
+	s.DBDerivedEntryCount = count
+}
+
+var _ Metrics = (*stubMetrics)(nil)
+
+type setupFn func(t *testing.T, db *DB, m *stubMetrics)
+
+type assertFn func(t *testing.T, db *DB, m *stubMetrics)
+
+func runDBTest(t *testing.T, setup setupFn, assert assertFn) {
+	createDb := func(t *testing.T, dir string) (*DB, *stubMetrics, string) {
+		logger := testlog.Logger(t, log.LvlTrace)
+		path := filepath.Join(dir, "test.db")
+		m := &stubMetrics{}
+		db, err := NewFromFile(logger, m, path)
+		require.NoError(t, err, "Failed to create database")
+		t.Cleanup(func() {
+			err := db.Close()
+			if err != nil {
+				require.ErrorIs(t, err, fs.ErrClosed)
+			}
+		})
+		return db, m, path
+	}
+
+	t.Run("New", func(t *testing.T) {
+		db, m, _ := createDb(t, t.TempDir())
+		setup(t, db, m)
+		assert(t, db, m)
+	})
+
+	t.Run("Existing", func(t *testing.T) {
+		dir := t.TempDir()
+		db, m, path := createDb(t, dir)
+		setup(t, db, m)
+		// Close and recreate the database
+		require.NoError(t, db.Close())
+		checkDBInvariants(t, path, m)
+
+		db2, m, path := createDb(t, dir)
+		assert(t, db2, m)
+		checkDBInvariants(t, path, m)
+	})
+}
+
+func TestEmptyDB(t *testing.T) {
+	runDBTest(t,
+		func(t *testing.T, db *DB, m *stubMetrics) {},
+		func(t *testing.T, db *DB, m *stubMetrics) {
+			_, _, err := db.Latest()
+			require.ErrorIs(t, err, entrydb.ErrFuture)
+
+			_, _, err = db.Latest()
+			require.ErrorIs(t, err, entrydb.ErrFuture)
+
+			_, err = db.LastDerivedAt(eth.BlockID{})
+			require.ErrorIs(t, err, entrydb.ErrFuture)
+
+			_, err = db.DerivedFrom(eth.BlockID{})
+			require.ErrorIs(t, err, entrydb.ErrFuture)
+		})
+}
+
+func mockL1(i uint64) types.BlockSeal {
+	return types.BlockSeal{
+		Hash:      crypto.Keccak256Hash([]byte(fmt.Sprintf("L1 block %d", i))),
+		Number:    i,
+		Timestamp: 1000_000 + i*12,
+	}
+}
+
+func mockL2(i uint64) types.BlockSeal {
+	var h common.Hash
+	if i != 0 {
+		h = crypto.Keccak256Hash([]byte(fmt.Sprintf("L1 block %d", i)))
+	}
+	return types.BlockSeal{
+		Hash:      h,
+		Number:    i,
+		Timestamp: 1000_000 + i*12,
+	}
+}
+
+func toRef(seal types.BlockSeal, parentHash common.Hash) eth.BlockRef {
+	return eth.BlockRef{
+		Hash:       seal.Hash,
+		Number:     seal.Number,
+		ParentHash: parentHash,
+		Time:       seal.Timestamp,
+	}
+}
+
+func TestSingleEntryDB(t *testing.T) {
+	expectedDerivedFrom := mockL1(1)
+	expectedDerived := mockL2(2)
+	runDBTest(t,
+		func(t *testing.T, db *DB, m *stubMetrics) {
+			require.NoError(t, db.AddDerived(toRef(expectedDerivedFrom, mockL1(0).Hash), toRef(expectedDerived, mockL2(0).Hash)))
+		},
+		func(t *testing.T, db *DB, m *stubMetrics) {
+			derivedFrom, derived, err := db.Latest()
+			require.NoError(t, err)
+			require.Equal(t, expectedDerivedFrom, derivedFrom)
+			require.Equal(t, expectedDerived, derived)
+
+			derived, err = db.LastDerivedAt(expectedDerivedFrom.ID())
+			require.NoError(t, err)
+			require.Equal(t, expectedDerived, derived)
+
+			_, err = db.LastDerivedAt(eth.BlockID{Hash: common.Hash{0xaa}, Number: expectedDerivedFrom.Number})
+			require.ErrorIs(t, err, entrydb.ErrConflict)
+
+			derivedFrom, err = db.DerivedFrom(expectedDerived.ID())
+			require.NoError(t, err)
+			require.Equal(t, expectedDerivedFrom, derivedFrom)
+
+			_, err = db.DerivedFrom(eth.BlockID{Hash: common.Hash{0xbb}, Number: expectedDerived.Number})
+			require.ErrorIs(t, err, entrydb.ErrConflict)
+		})
+}
+
+func TestTwoEntryDB(t *testing.T) {
+	l1Block0 := mockL1(0)
+	l1Block1 := mockL1(1)
+	l1Block2 := mockL1(2)
+
+	l2Block0 := mockL2(0)
+	l2Block1 := mockL2(1)
+	l2Block2 := mockL2(2)
+
+	runDBTest(t, func(t *testing.T, db *DB, m *stubMetrics) {
+		require.NoError(t, db.AddDerived(toRef(l1Block0, common.Hash{}), toRef(l2Block0, common.Hash{})))
+		require.NoError(t, db.AddDerived(toRef(l1Block1, l1Block0.Hash), toRef(l2Block1, l2Block0.Hash)))
+		require.NoError(t, db.AddDerived(toRef(l1Block2, l1Block1.Hash), toRef(l2Block2, l2Block1.Hash)))
+	}, func(t *testing.T, db *DB, m *stubMetrics) {
+
+		derivedFrom, derived, err := db.Latest()
+		require.NoError(t, err)
+		require.Equal(t, l1Block2, derivedFrom)
+		require.Equal(t, l2Block2, derived)
+
+		derived, err = db.LastDerivedAt(l1Block2.ID())
+		require.NoError(t, err)
+		require.Equal(t, l2Block2, derived)
+
+		_, err = db.LastDerivedAt(eth.BlockID{Hash: common.Hash{0xaa}, Number: l1Block2.Number})
+		require.ErrorIs(t, err, entrydb.ErrConflict)
+
+		derivedFrom, err = db.DerivedFrom(l2Block2.ID())
+		require.NoError(t, err)
+		require.Equal(t, l1Block2, derivedFrom)
+
+		_, err = db.DerivedFrom(eth.BlockID{Hash: common.Hash{0xbb}, Number: l2Block2.Number})
+		require.ErrorIs(t, err, entrydb.ErrConflict)
+
+		derived, err = db.LastDerivedAt(l1Block1.ID())
+		require.NoError(t, err)
+		require.Equal(t, l2Block1, derived)
+
+		derivedFrom, err = db.DerivedFrom(l2Block1.ID())
+		require.NoError(t, err)
+		require.Equal(t, l1Block1, derivedFrom)
+
+		derived, err = db.LastDerivedAt(l1Block0.ID())
+		require.NoError(t, err)
+		require.Equal(t, l2Block0, derived)
+
+		derivedFrom, err = db.DerivedFrom(l2Block0.ID())
+		require.NoError(t, err)
+		require.Equal(t, l1Block0, derivedFrom)
+	})
+}
+
+// TestFastL2Batcher tests what happens if we have derived multiple L2 blocks from the same L1 block
+func TestFastL2Batcher(t *testing.T) {
+	l1Block0 := mockL1(0)
+	l1Block1 := mockL1(1)
+	l1Block2 := mockL1(2)
+
+	l2Block0 := mockL2(0)
+	l2Block1 := mockL2(1)
+	l2Block2 := mockL2(2)
+	l2Block3 := mockL2(3)
+	l2Block4 := mockL2(4)
+	l2Block5 := mockL2(5)
+
+	runDBTest(t, func(t *testing.T, db *DB, m *stubMetrics) {
+		// L2 genesis derived from L1 genesis
+		require.NoError(t, db.AddDerived(toRef(l1Block0, common.Hash{}), toRef(l2Block0, common.Hash{})))
+		// Many L2 blocks all derived from same L1 block
+		l1Ref1 := toRef(l1Block1, l1Block0.Hash)
+		require.NoError(t, db.AddDerived(l1Ref1, toRef(l2Block1, l2Block0.Hash)))
+		require.NoError(t, db.AddDerived(l1Ref1, toRef(l2Block2, l2Block1.Hash)))
+		require.NoError(t, db.AddDerived(l1Ref1, toRef(l2Block3, l2Block2.Hash)))
+		require.NoError(t, db.AddDerived(l1Ref1, toRef(l2Block4, l2Block3.Hash)))
+		// Latest L2 block derived from later L1 block
+		require.NoError(t, db.AddDerived(toRef(l1Block2, l1Block1.Hash), toRef(l2Block5, l2Block4.Hash)))
+	}, func(t *testing.T, db *DB, m *stubMetrics) {
+
+		derivedFrom, derived, err := db.Latest()
+		require.NoError(t, err)
+		require.Equal(t, l1Block2, derivedFrom)
+		require.Equal(t, l2Block5, derived)
+
+		derived, err = db.LastDerivedAt(l1Block2.ID())
+		require.NoError(t, err)
+		require.Equal(t, l2Block5, derived)
+
+		// test what tip was derived from
+		derivedFrom, err = db.DerivedFrom(l2Block5.ID())
+		require.NoError(t, err)
+		require.Equal(t, l1Block2, derivedFrom)
+
+		// Multiple L2 blocks all derived from same older L1 block
+		for _, b := range []types.BlockSeal{l2Block1, l2Block2, l2Block3, l2Block4} {
+			derivedFrom, err = db.DerivedFrom(b.ID())
+			require.NoError(t, err)
+			require.Equal(t, l1Block1, derivedFrom)
+		}
+
+		// test that the latest L2 counts, not the intermediate
+		derived, err = db.LastDerivedAt(l1Block1.ID())
+		require.NoError(t, err)
+		require.Equal(t, l2Block4, derived)
+
+	})
+}
+
+// TestSlowL2Batcher tests what happens if we have derived no new L2 blocks in a L1 block
+func TestSlowL2Batcher(t *testing.T) {
+	l1Block0 := mockL1(0)
+	l1Block1 := mockL1(1)
+	l1Block2 := mockL1(2)
+	l1Block3 := mockL1(3)
+	l1Block4 := mockL1(4)
+	l1Block5 := mockL1(5)
+
+	l2Block0 := mockL2(0)
+	l2Block1 := mockL2(1)
+	l2Block2 := mockL2(2)
+
+	runDBTest(t, func(t *testing.T, db *DB, m *stubMetrics) {
+		// L2 genesis derived from L1 genesis
+		require.NoError(t, db.AddDerived(toRef(l1Block0, common.Hash{}), toRef(l2Block0, common.Hash{})))
+		// Many L1 blocks all repeating the same L2 block
+		l2Ref1 := toRef(l2Block1, l2Block0.Hash)
+		require.NoError(t, db.AddDerived(toRef(l1Block1, l1Block0.Hash), l2Ref1))
+		require.NoError(t, db.AddDerived(toRef(l1Block2, l1Block1.Hash), l2Ref1))
+		require.NoError(t, db.AddDerived(toRef(l1Block3, l1Block2.Hash), l2Ref1))
+		require.NoError(t, db.AddDerived(toRef(l1Block4, l1Block3.Hash), l2Ref1))
+		// New L1 block that finally produces a new L2 block
+		require.NoError(t, db.AddDerived(toRef(l1Block5, l1Block4.Hash), toRef(l2Block2, l2Block1.Hash)))
+	}, func(t *testing.T, db *DB, m *stubMetrics) {
+
+		derivedFrom, derived, err := db.Latest()
+		require.NoError(t, err)
+		require.Equal(t, l1Block5, derivedFrom)
+		require.Equal(t, l2Block2, derived)
+
+		// test what we last derived at the tip
+		derived, err = db.LastDerivedAt(l1Block5.ID())
+		require.NoError(t, err)
+		require.Equal(t, l2Block2, derived)
+
+		// Multiple L1 blocks all copying the last known derived L2 block
+		for _, b := range []types.BlockSeal{l1Block1, l1Block2, l1Block3, l1Block4} {
+			derived, err = db.LastDerivedAt(b.ID())
+			require.NoError(t, err)
+			require.Equal(t, l2Block1, derived)
+		}
+
+		// test that the first L1 counts, not the ones that repeat the L2 info
+		derivedFrom, err = db.DerivedFrom(l2Block1.ID())
+		require.NoError(t, err)
+		require.Equal(t, l1Block1, derivedFrom)
+	})
+}
+
+func TestManyEntryDB(t *testing.T) {
+	t.Run("at genesis", func(t *testing.T) {
+		testManyEntryDB(t, 0, 0)
+	})
+	t.Run("start at arbitrary L1 block", func(t *testing.T) {
+		testManyEntryDB(t, 30000, 0)
+	})
+	t.Run("start at arbitrary L2 block", func(t *testing.T) {
+		testManyEntryDB(t, 0, 30000)
+	})
+	t.Run("start at arbitrary L1 and L2 block", func(t *testing.T) {
+		testManyEntryDB(t, 2000000, 1000000)
+	})
+}
+
+func testManyEntryDB(t *testing.T, offsetL1 uint64, offsetL2 uint64) {
+	// L2 -> first L1 occurrence
+	firstDerivedFrom := make(map[eth.BlockID]types.BlockSeal)
+	// L1 -> last L2 occurrence
+	lastDerived := make(map[eth.BlockID]types.BlockSeal)
+
+	runDBTest(t, func(t *testing.T, db *DB, m *stubMetrics) {
+		// Insert genesis
+		require.NoError(t, db.AddDerived(toRef(mockL1(offsetL1), common.Hash{}), toRef(mockL2(offsetL2), common.Hash{})))
+		firstDerivedFrom[mockL2(offsetL2).ID()] = mockL1(offsetL1)
+		lastDerived[mockL1(offsetL1).ID()] = mockL2(offsetL2)
+
+		rng := rand.New(rand.NewSource(1234))
+		// Insert 1000 randomly generated entries, derived at random bumps in L1
+		for i := uint64(0); i < 1000; i++ {
+			derivedFrom, derived, err := db.Latest()
+			require.NoError(t, err)
+
+			switch rng.Intn(3) {
+			case 0: // bump L1
+				derivedFrom = mockL1(derivedFrom.Number + 1)
+			case 1: // bump L2
+				derived = mockL2(derived.Number + 1)
+			case 2: // bump both
+				derivedFrom = mockL1(derivedFrom.Number + 1)
+				derived = mockL2(derived.Number + 1)
+			}
+			derivedFromRef := toRef(derivedFrom, mockL1(derivedFrom.Number-1).Hash)
+			derivedRef := toRef(derived, mockL2(derived.Number-1).Hash)
+			lastDerived[derivedFromRef.ID()] = derived
+			if _, ok := firstDerivedFrom[derivedRef.ID()]; !ok {
+				firstDerivedFrom[derivedRef.ID()] = derivedFrom
+			}
+			require.NoError(t, db.AddDerived(derivedFromRef, derivedRef))
+		}
+	}, func(t *testing.T, db *DB, m *stubMetrics) {
+		// Now assert we can find what they are all derived from, and match the expectations.
+		derivedFrom, derived, err := db.Latest()
+		require.NoError(t, err)
+		require.NotZero(t, derivedFrom.Number-offsetL1)
+		require.NotZero(t, derived.Number-offsetL2)
+
+		for i := offsetL1; i <= derivedFrom.Number; i++ {
+			l1ID := mockL1(i).ID()
+			derived, err := db.LastDerivedAt(l1ID)
+			require.NoError(t, err)
+			require.Contains(t, lastDerived, l1ID)
+			require.Equal(t, lastDerived[l1ID], derived)
+		}
+
+		for i := offsetL2; i <= derived.Number; i++ {
+			l2ID := mockL2(i).ID()
+			derivedFrom, err := db.DerivedFrom(l2ID)
+			require.NoError(t, err)
+			require.Contains(t, firstDerivedFrom, l2ID)
+			require.Equal(t, firstDerivedFrom[l2ID], derivedFrom)
+		}
+
+		// if not started at genesis, try to read older data, assert it's unavailable.
+		if offsetL1 > 0 {
+			_, err := db.LastDerivedAt(mockL1(0).ID())
+			require.ErrorIs(t, err, entrydb.ErrSkipped)
+
+			_, err = db.LastDerivedAt(mockL1(offsetL1 - 1).ID())
+			require.ErrorIs(t, err, entrydb.ErrSkipped)
+		}
+		if offsetL2 > 0 {
+			_, err := db.DerivedFrom(mockL2(0).ID())
+			require.ErrorIs(t, err, entrydb.ErrSkipped)
+
+			_, err = db.DerivedFrom(mockL2(offsetL2 - 1).ID())
+			require.ErrorIs(t, err, entrydb.ErrSkipped)
+		}
+	})
+}
+
+// TestRewind tests what happens if we rewind
+func TestRewind(t *testing.T) {
+	l1Block0 := mockL1(0)
+	l1Block1 := mockL1(1)
+	l1Block2 := mockL1(2)
+	l1Block3 := mockL1(3)
+	l1Block4 := mockL1(4)
+	l1Block5 := mockL1(5)
+
+	l2Block0 := mockL2(0)
+	l2Block1 := mockL2(1)
+	l2Block2 := mockL2(2)
+
+	runDBTest(t, func(t *testing.T, db *DB, m *stubMetrics) {
+		// L2 genesis derived from L1 genesis
+		require.NoError(t, db.AddDerived(toRef(l1Block0, common.Hash{}), toRef(l2Block0, common.Hash{})))
+		// Many L1 blocks all repeating the same L2 block
+		l2Ref1 := toRef(l2Block1, l2Block0.Hash)
+		require.NoError(t, db.AddDerived(toRef(l1Block1, l1Block0.Hash), l2Ref1))
+		require.NoError(t, db.AddDerived(toRef(l1Block2, l1Block1.Hash), l2Ref1))
+		require.NoError(t, db.AddDerived(toRef(l1Block3, l1Block2.Hash), l2Ref1))
+		require.NoError(t, db.AddDerived(toRef(l1Block4, l1Block3.Hash), l2Ref1))
+		// New L1 block that finally produces a new L2 block
+		require.NoError(t, db.AddDerived(toRef(l1Block5, l1Block4.Hash), toRef(l2Block2, l2Block1.Hash)))
+	}, func(t *testing.T, db *DB, m *stubMetrics) {
+
+		derivedFrom, derived, err := db.Latest()
+		require.NoError(t, err)
+		require.Equal(t, l1Block5, derivedFrom)
+		require.Equal(t, l2Block2, derived)
+
+		// Rewind to the future
+		require.ErrorIs(t, db.Rewind(6), entrydb.ErrFuture)
+
+		// Rewind to the exact block we're at
+		require.NoError(t, db.Rewind(l1Block5.Number))
+		derivedFrom, derived, err = db.Latest()
+		require.NoError(t, err)
+		require.Equal(t, l1Block5, derivedFrom)
+		require.Equal(t, l2Block2, derived)
+
+		// Now rewind to L1 block 3 (inclusive).
+		require.NoError(t, db.Rewind(l1Block3.Number))
+
+		// See if we find consistent data
+		derivedFrom, derived, err = db.Latest()
+		require.NoError(t, err)
+		require.Equal(t, l1Block3, derivedFrom)
+		require.Equal(t, l2Block1, derived)
+
+		// Rewind further to L1 block 1 (inclusive).
+		require.NoError(t, db.Rewind(l1Block1.Number))
+		derivedFrom, derived, err = db.Latest()
+		require.NoError(t, err)
+		require.Equal(t, l1Block1, derivedFrom)
+		require.Equal(t, l2Block1, derived)
+
+		// Rewind further to L1 block 0 (inclusive).
+		require.NoError(t, db.Rewind(l1Block0.Number))
+		derivedFrom, derived, err = db.Latest()
+		require.NoError(t, err)
+		require.Equal(t, l1Block0, derivedFrom)
+		require.Equal(t, l2Block0, derived)
+	})
+}

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

+package fromda
+
+import (
+	"encoding/binary"
+	"fmt"
+	"io"
+
+	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend/db/entrydb"
+	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/types"
+)
+
+const EntrySize = 100
+
+type Entry [EntrySize]byte
+
+func (e Entry) Type() EntryType {
+	return EntryType(e[0])
+}
+
+type EntryType uint8
+
+const (
+	DerivedFromV0 EntryType = 0
+)
+
+func (s EntryType) String() string {
+	switch s {
+	case DerivedFromV0:
+		return "v0"
+	default:
+		return fmt.Sprintf("unknown(%d)", uint8(s))
+	}
+}
+
+type EntryBinary struct{}
+
+func (EntryBinary) Append(dest []byte, e *Entry) []byte {
+	return append(dest, e[:]...)
+}
+
+func (EntryBinary) ReadAt(dest *Entry, r io.ReaderAt, at int64) (n int, err error) {
+	return r.ReadAt(dest[:], at)
+}
+
+func (EntryBinary) EntrySize() int {
+	return EntrySize
+}
+
+type LinkEntry struct {
+	derivedFrom types.BlockSeal
+	derived     types.BlockSeal
+}
+
+func (d LinkEntry) String() string {
+	return fmt.Sprintf("LinkEntry(derivedFrom: %s, derived: %s)", d.derivedFrom, d.derived)
+}
+
+func (d *LinkEntry) decode(e Entry) error {
+	if e.Type() != DerivedFromV0 {
+		return fmt.Errorf("%w: unexpected entry type: %s", entrydb.ErrDataCorruption, e.Type())
+	}
+	if [3]byte(e[1:4]) != ([3]byte{}) {
+		return fmt.Errorf("%w: expected empty data, to pad entry size to round number: %x", entrydb.ErrDataCorruption, e[1:4])
+	}
+	offset := 4
+	d.derivedFrom.Number = binary.BigEndian.Uint64(e[offset : offset+8])
+	offset += 8
+	d.derivedFrom.Timestamp = binary.BigEndian.Uint64(e[offset : offset+8])
+	offset += 8
+	d.derived.Number = binary.BigEndian.Uint64(e[offset : offset+8])
+	offset += 8
+	d.derived.Timestamp = binary.BigEndian.Uint64(e[offset : offset+8])
+	offset += 8
+	copy(d.derivedFrom.Hash[:], e[offset:offset+32])
+	offset += 32
+	copy(d.derived.Hash[:], e[offset:offset+32])
+	return nil
+}
+
+func (d *LinkEntry) encode() Entry {
+	var out Entry
+	out[0] = uint8(DerivedFromV0)
+	offset := 4
+	binary.BigEndian.PutUint64(out[offset:offset+8], d.derivedFrom.Number)
+	offset += 8
+	binary.BigEndian.PutUint64(out[offset:offset+8], d.derivedFrom.Timestamp)
+	offset += 8
+	binary.BigEndian.PutUint64(out[offset:offset+8], d.derived.Number)
+	offset += 8
+	binary.BigEndian.PutUint64(out[offset:offset+8], d.derived.Timestamp)
+	offset += 8
+	copy(out[offset:offset+32], d.derivedFrom.Hash[:])
+	offset += 32
+	copy(out[offset:offset+32], d.derived.Hash[:])
+	return out
+}

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

+package fromda
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/ethereum/go-ethereum/common"
+
+	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/types"
+)
+
+func FuzzRoundtripLinkEntry(f *testing.F) {
+	f.Fuzz(func(t *testing.T, aHash []byte, aNum uint64, aTimestamp uint64, bHash []byte, bNum uint64, bTimestamp uint64) {
+		x := LinkEntry{
+			derivedFrom: types.BlockSeal{
+				Hash:      common.BytesToHash(aHash),
+				Number:    aNum,
+				Timestamp: aTimestamp,
+			},
+			derived: types.BlockSeal{
+				Hash:      common.BytesToHash(bHash),
+				Number:    bNum,
+				Timestamp: bTimestamp,
+			},
+		}
+		entry := x.encode()
+		require.Equal(t, DerivedFromV0, entry.Type())
+		var y LinkEntry
+		err := y.decode(entry)
+		require.NoError(t, err)
+		require.Equal(t, x, y)
+	})
+}
+
+func TestLinkEntry(t *testing.T) {
+	t.Run("invalid type", func(t *testing.T) {
+		var entry Entry
+		entry[0] = 123
+		var x LinkEntry
+		require.ErrorContains(t, x.decode(entry), "unexpected")
+	})
+}

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

+package fromda
+
+import (
+	"fmt"
+
+	"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/types"
+)
+
+func (db *DB) AddDerived(derivedFrom eth.BlockRef, derived eth.BlockRef) error {
+	db.rwLock.Lock()
+	defer db.rwLock.Unlock()
+
+	// If we don't have any entries yet, allow any block to start things off
+	if db.store.Size() == 0 {
+		link := LinkEntry{
+			derivedFrom: types.BlockSeal{
+				Hash:      derivedFrom.Hash,
+				Number:    derivedFrom.Number,
+				Timestamp: derivedFrom.Time,
+			},
+			derived: types.BlockSeal{
+				Hash:      derived.Hash,
+				Number:    derived.Number,
+				Timestamp: derived.Time,
+			},
+		}
+		e := link.encode()
+		if err := db.store.Append(e); err != nil {
+			return err
+		}
+		db.m.RecordDBDerivedEntryCount(db.store.Size())
+		return nil
+	}
+
+	lastDerivedFrom, lastDerived, err := db.latest()
+	if err != nil {
+		return err
+	}
+
+	if lastDerived.ID() == derived.ID() && lastDerivedFrom.ID() == derivedFrom.ID() {
+		// it shouldn't be possible, but the ID component of a block ref doesn't include the timestamp
+		// so if the timestampt doesn't match, still return no error to the caller, but at least log a warning
+		if lastDerived.Timestamp != derived.Time {
+			db.log.Warn("Derived block already exists with different timestamp", "derived", derived, "lastDerived", lastDerived)
+		}
+		if lastDerivedFrom.Timestamp != derivedFrom.Time {
+			db.log.Warn("Derived-from block already exists with different timestamp", "derivedFrom", derivedFrom, "lastDerivedFrom", lastDerivedFrom)
+		}
+		// Repeat of same information. No entries to be written.
+		// But we can silently ignore and not return an error, as that brings the caller
+		// in a consistent state, after which it can insert the actual new derived-from information.
+		return nil
+	}
+
+	// Check derived relation: the L2 chain has to be sequential without gaps. An L2 block may repeat if the L1 block is empty.
+	if lastDerived.Number == derived.Number {
+		// Same block height? Then it must be the same block.
+		// I.e. we encountered an empty L1 block, and the same L2 block continues to be the last block that was derived from it.
+		if lastDerived.Hash != derived.Hash {
+			return fmt.Errorf("derived block %s conflicts with known derived block %s at same height: %w",
+				derived, lastDerived, entrydb.ErrConflict)
+		}
+	} else if lastDerived.Number+1 == derived.Number {
+		if lastDerived.Hash != derived.ParentHash {
+			return fmt.Errorf("derived block %s (parent %s) does not build on %s: %w",
+				derived, derived.ParentHash, lastDerived, entrydb.ErrConflict)
+		}
+	} else if lastDerived.Number+1 < derived.Number {
+		return fmt.Errorf("derived block %s (parent: %s) is too new, expected to build on top of %s: %w",
+			derived, derived.ParentHash, lastDerived, entrydb.ErrOutOfOrder)
+	} else {
+		return fmt.Errorf("derived block %s is older than current derived block %s: %w",
+			derived, lastDerived, entrydb.ErrOutOfOrder)
+	}
+
+	// Check derived-from relation: multiple L2 blocks may be derived from the same L1 block. But everything in sequence.
+	if lastDerivedFrom.Number == derivedFrom.Number {
+		// Same block height? Then it must be the same block.
+		if lastDerivedFrom.Hash != derivedFrom.Hash {
+			return fmt.Errorf("cannot add block %s as derived from %s, expected to be derived from %s at this block height: %w",
+				derived, derivedFrom, lastDerivedFrom, entrydb.ErrConflict)
+		}
+	} else if lastDerivedFrom.Number+1 == derivedFrom.Number {
+		// parent hash check
+		if lastDerivedFrom.Hash != derivedFrom.ParentHash {
+			return fmt.Errorf("cannot add block %s as derived from %s (parent %s) derived on top of %s: %w",
+				derived, derivedFrom, derivedFrom.ParentHash, lastDerivedFrom, entrydb.ErrConflict)
+		}
+	} else if lastDerivedFrom.Number+1 < derivedFrom.Number {
+		// adding block that is derived from something too far into the future
+		return fmt.Errorf("cannot add block %s as derived from %s, still deriving from %s: %w",
+			derived, derivedFrom, lastDerivedFrom, entrydb.ErrOutOfOrder)
+	} else {
+		// adding block that is derived from something too old
+		return fmt.Errorf("cannot add block %s as derived from %s, deriving already at %s: %w",
+			derived, derivedFrom, lastDerivedFrom, entrydb.ErrOutOfOrder)
+	}
+
+	link := LinkEntry{
+		derivedFrom: types.BlockSeal{
+			Hash:      derivedFrom.Hash,
+			Number:    derivedFrom.Number,
+			Timestamp: derivedFrom.Time,
+		},
+		derived: types.BlockSeal{
+			Hash:      derived.Hash,
+			Number:    derived.Number,
+			Timestamp: derived.Time,
+		},
+	}
+	e := link.encode()
+	if err := db.store.Append(e); err != nil {
+		return err
+	}
+	db.m.RecordDBDerivedEntryCount(db.store.Size())
+	return nil
+}

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

+package fromda
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/ethereum/go-ethereum/common"
+
+	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend/db/entrydb"
+	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/types"
+)
+
+type testCase struct {
+	name     string
+	setupFn  setupFn
+	assertFn assertFn
+}
+
+func TestBadUpdates(t *testing.T) {
+	aDerivedFrom := mockL1(1)
+	aDerived := mockL2(201)
+	bDerivedFrom := mockL1(2)
+	bDerived := mockL2(202)
+	cDerivedFrom := mockL1(3)
+	cDerived := mockL2(203)
+	dDerivedFrom := mockL1(4)
+	dDerived := mockL2(204)
+	eDerivedFrom := mockL1(5)
+	eDerived := mockL2(205)
+	fDerivedFrom := mockL1(6)
+	fDerived := mockL2(206)
+
+	noChange := assertFn(func(t *testing.T, db *DB, m *stubMetrics) {
+		derivedFrom, derived, err := db.Latest()
+		require.NoError(t, err)
+		require.Equal(t, dDerivedFrom, derivedFrom)
+		require.Equal(t, dDerived, derived)
+	})
+
+	testCases := []testCase{
+		{
+			name: "add on old derivedFrom",
+			setupFn: func(t *testing.T, db *DB, m *stubMetrics) {
+				require.ErrorIs(t, db.AddDerived(toRef(bDerivedFrom, aDerivedFrom.Hash), toRef(dDerived, cDerived.Hash)), entrydb.ErrOutOfOrder)
+			},
+			assertFn: noChange,
+		},
+		{
+			name: "repeat parent derivedFrom",
+			setupFn: func(t *testing.T, db *DB, m *stubMetrics) {
+				require.ErrorIs(t, db.AddDerived(toRef(cDerivedFrom, bDerivedFrom.Hash), toRef(dDerived, cDerived.Hash)), entrydb.ErrOutOfOrder)
+			},
+			assertFn: noChange,
+		},
+		{
+			name: "add on conflicting derivedFrom, same height. And new derived value",
+			setupFn: func(t *testing.T, db *DB, m *stubMetrics) {
+				require.ErrorIs(t, db.AddDerived(toRef(types.BlockSeal{
+					Hash:      common.Hash{0xba, 0xd},
+					Number:    dDerivedFrom.Number,
+					Timestamp: dDerivedFrom.Timestamp,
+				}, cDerivedFrom.Hash), toRef(eDerived, dDerived.Hash)), entrydb.ErrConflict)
+			},
+			assertFn: noChange,
+		},
+		{
+			name: "DerivedFrom with conflicting parent root, same L1 height, new L2: accepted, L1 parent-hash is used only on L1 increments.",
+			setupFn: func(t *testing.T, db *DB, m *stubMetrics) {
+				require.NoError(t, db.AddDerived(toRef(dDerivedFrom, common.Hash{0x42}), toRef(eDerived, dDerived.Hash)), entrydb.ErrConflict)
+			},
+			assertFn: func(t *testing.T, db *DB, m *stubMetrics) {
+				derivedFrom, derived, err := db.Latest()
+				require.NoError(t, err)
+				require.Equal(t, dDerivedFrom, derivedFrom)
+				require.Equal(t, eDerived, derived)
+			},
+		},
+		{
+			name: "Conflicting derivedFrom parent root, new L1 height, same L2",
+			setupFn: func(t *testing.T, db *DB, m *stubMetrics) {
+				require.ErrorIs(t, db.AddDerived(toRef(eDerivedFrom, common.Hash{0x42}), toRef(dDerived, cDerived.Hash)), entrydb.ErrConflict)
+			},
+			assertFn: noChange,
+		},
+		{
+			name: "add on too new derivedFrom (even if parent-hash looks correct)",
+			setupFn: func(t *testing.T, db *DB, m *stubMetrics) {
+				require.ErrorIs(t, db.AddDerived(toRef(fDerivedFrom, dDerivedFrom.Hash), toRef(eDerived, dDerived.Hash)), entrydb.ErrOutOfOrder)
+			},
+			assertFn: noChange,
+		},
+		{
+			name: "add on old derivedFrom (even if parent-hash looks correct)",
+			setupFn: func(t *testing.T, db *DB, m *stubMetrics) {
+				require.ErrorIs(t, db.AddDerived(toRef(cDerivedFrom, bDerivedFrom.Hash), toRef(cDerived, dDerived.Hash)), entrydb.ErrOutOfOrder)
+			},
+			assertFn: noChange,
+		},
+		{
+			name: "add on even older derivedFrom",
+			setupFn: func(t *testing.T, db *DB, m *stubMetrics) {
+				require.ErrorIs(t, db.AddDerived(toRef(bDerivedFrom, aDerivedFrom.Hash), toRef(dDerived, cDerived.Hash)), entrydb.ErrOutOfOrder)
+			},
+			assertFn: noChange,
+		},
+		{
+			name: "add on conflicting derived, same L2 height, new L1 block",
+			setupFn: func(t *testing.T, db *DB, m *stubMetrics) {
+				require.ErrorIs(t, db.AddDerived(toRef(eDerivedFrom, dDerivedFrom.Hash), toRef(types.BlockSeal{
+					Hash:      common.Hash{0x42},
+					Number:    dDerived.Number,
+					Timestamp: dDerived.Timestamp,
+				}, cDerived.Hash)), entrydb.ErrConflict)
+			},
+			assertFn: noChange,
+		},
+		{
+			name: "add derived with conflicting parent hash, new L1 height, same L2 height: accepted, L2 parent-hash is only checked on L2 increments.",
+			setupFn: func(t *testing.T, db *DB, m *stubMetrics) {
+				require.NoError(t, db.AddDerived(toRef(eDerivedFrom, dDerivedFrom.Hash), toRef(dDerived, common.Hash{0x42})), entrydb.ErrConflict)
+			},
+			assertFn: func(t *testing.T, db *DB, m *stubMetrics) {
+				derivedFrom, derived, err := db.Latest()
+				require.NoError(t, err)
+				require.Equal(t, eDerivedFrom, derivedFrom)
+				require.Equal(t, dDerived, derived)
+			},
+		},
+		{
+			name: "add derived with conflicting parent hash, same L1 height, new L2 height",
+			setupFn: func(t *testing.T, db *DB, m *stubMetrics) {
+				require.ErrorIs(t, db.AddDerived(toRef(dDerivedFrom, cDerivedFrom.Hash), toRef(eDerived, common.Hash{0x42})), entrydb.ErrConflict)
+			},
+			assertFn: noChange,
+		},
+		{
+			name: "add on too new derived (even if parent-hash looks correct)",
+			setupFn: func(t *testing.T, db *DB, m *stubMetrics) {
+				require.ErrorIs(t, db.AddDerived(toRef(dDerivedFrom, cDerivedFrom.Hash), toRef(fDerived, dDerived.Hash)), entrydb.ErrOutOfOrder)
+			},
+			assertFn: noChange,
+		},
+		{
+			name: "add on old derived (even if parent-hash looks correct)",
+			setupFn: func(t *testing.T, db *DB, m *stubMetrics) {
+				require.ErrorIs(t, db.AddDerived(toRef(dDerivedFrom, cDerivedFrom.Hash), toRef(cDerived, bDerived.Hash)), entrydb.ErrOutOfOrder)
+			},
+			assertFn: noChange,
+		},
+		{
+			name: "add on even older derived",
+			setupFn: func(t *testing.T, db *DB, m *stubMetrics) {
+				require.ErrorIs(t, db.AddDerived(toRef(dDerivedFrom, cDerivedFrom.Hash), toRef(bDerived, aDerived.Hash)), entrydb.ErrOutOfOrder)
+			},
+			assertFn: noChange,
+		},
+		{
+			name: "repeat self, silent no-op",
+			setupFn: func(t *testing.T, db *DB, m *stubMetrics) {
+				pre := m.DBDerivedEntryCount
+				require.NoError(t, db.AddDerived(toRef(dDerivedFrom, cDerivedFrom.Hash), toRef(dDerived, cDerived.Hash)), entrydb.ErrOutOfOrder)
+				require.Equal(t, pre, m.DBDerivedEntryCount)
+			},
+			assertFn: noChange,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			runDBTest(t,
+				func(t *testing.T, db *DB, m *stubMetrics) {
+					// Good first entry
+					require.NoError(t, db.AddDerived(toRef(dDerivedFrom, cDerivedFrom.Hash), toRef(dDerived, cDerived.Hash)))
+					// apply the test-case setup
+					tc.setupFn(t, db, m)
+				},
+				tc.assertFn)
+		})
+	}
+}

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

@@ -25,15 +25,6 @@ type Metrics interface {
 	RecordDBSearchEntriesRead(count int64)
 }
 
-type EntryStore interface {
-	Size() int64
-	LastEntryIdx() entrydb.EntryIdx
-	Read(idx entrydb.EntryIdx) (Entry, error)
-	Append(entries ...Entry) error
-	Truncate(idx entrydb.EntryIdx) error
-	Close() error
-}
-
 // DB implements an append only database for log data and cross-chain dependencies.
 //
 // To keep the append-only format, reduce data size, and support reorg detection and registering of executing-messages:
@@ -44,21 +35,21 @@ type EntryStore interface {
 type DB struct {
 	log    log.Logger
 	m      Metrics
-	store  EntryStore
+	store  entrydb.EntryStore[EntryType, Entry]
 	rwLock sync.RWMutex
 
 	lastEntryContext logContext
 }
 
 func NewFromFile(logger log.Logger, m Metrics, path string, trimToLastSealed bool) (*DB, error) {
-	store, err := entrydb.NewEntryDB[EntryType](logger, path)
+	store, err := entrydb.NewEntryDB[EntryType, Entry, EntryBinary](logger, path)
 	if err != nil {
 		return nil, fmt.Errorf("failed to open DB: %w", err)
 	}
 	return NewFromEntryStore(logger, m, store, trimToLastSealed)
 }
 
-func NewFromEntryStore(logger log.Logger, m Metrics, store EntryStore, trimToLastSealed bool) (*DB, error) {
+func NewFromEntryStore(logger log.Logger, m Metrics, store entrydb.EntryStore[EntryType, Entry], trimToLastSealed bool) (*DB, error) {
 	db := &DB{
 		log:   logger,
 		m:     m,

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

@@ -8,8 +8,6 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/require"
-
-	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend/db/entrydb"
 )
 
 type statInvariant func(stat os.FileInfo, m *stubMetrics) error
@@ -31,11 +29,11 @@ func checkDBInvariants(t *testing.T, dbPath string, m *stubMetrics) {
 	// Read all entries as binary blobs
 	file, err := os.OpenFile(dbPath, os.O_RDONLY, 0o644)
 	require.NoError(t, err)
-	entries := make([]Entry, stat.Size()/entrydb.EntrySize)
+	entries := make([]Entry, stat.Size()/EntrySize)
 	for i := range entries {
 		n, err := io.ReadFull(file, entries[i][:])
 		require.NoErrorf(t, err, "failed to read entry %v", i)
-		require.EqualValuesf(t, entrydb.EntrySize, n, "read wrong length for entry %v", i)
+		require.EqualValuesf(t, EntrySize, n, "read wrong length for entry %v", i)
 	}
 
 	entryInvariants := []entryInvariant{
@@ -67,16 +65,16 @@ func fmtEntries(entries []Entry) string {
 
 func invariantFileSizeMultipleOfEntrySize(stat os.FileInfo, _ *stubMetrics) error {
 	size := stat.Size()
-	if size%entrydb.EntrySize != 0 {
-		return fmt.Errorf("expected file size to be a multiple of entry size (%v) but was %v", entrydb.EntrySize, size)
+	if size%EntrySize != 0 {
+		return fmt.Errorf("expected file size to be a multiple of entry size (%v) but was %v", EntrySize, size)
 	}
 	return nil
 }
 
 func invariantFileSizeMatchesEntryCountMetric(stat os.FileInfo, m *stubMetrics) error {
 	size := stat.Size()
-	if m.entryCount*entrydb.EntrySize != size {
-		return fmt.Errorf("expected file size to be entryCount (%v) * entrySize (%v) = %v but was %v", m.entryCount, entrydb.EntrySize, m.entryCount*entrydb.EntrySize, size)
+	if m.entryCount*EntrySize != size {
+		return fmt.Errorf("expected file size to be entryCount (%v) * entrySize (%v) = %v but was %v", m.entryCount, EntrySize, m.entryCount*EntrySize, size)
 	}
 	return nil
 }

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

@@ -2,7 +2,6 @@ package logs
 
 import (
 	"encoding/binary"
-	"io"
 	"io/fs"
 	"os"
 	"path/filepath"
@@ -91,6 +90,7 @@ func TestLatestSealedBlockNum(t *testing.T) {
 				require.Zero(t, n)
 				idx, err := db.searchCheckpoint(0, 0)
 				require.ErrorIs(t, err, entrydb.ErrFuture, "no checkpoint in empty db")
+				require.ErrorIs(t, err, entrydb.ErrFuture, "no checkpoint in empty db")
 				require.Zero(t, idx)
 			})
 	})
@@ -124,6 +124,7 @@ func TestLatestSealedBlockNum(t *testing.T) {
 				require.Zero(t, idx, "anchor block as checkpoint 0")
 				_, err = db.searchCheckpoint(0, 0)
 				require.ErrorIs(t, err, entrydb.ErrSkipped, "no checkpoint before genesis")
+				require.ErrorIs(t, err, entrydb.ErrSkipped, "no checkpoint before genesis")
 			})
 	})
 	t.Run("Block 1 case", func(t *testing.T) {
@@ -176,6 +177,7 @@ func TestAddLog(t *testing.T) {
 				genesis := eth.BlockID{Hash: createHash(15), Number: 0}
 				err := db.AddLog(createHash(1), genesis, 0, nil)
 				require.ErrorIs(t, err, entrydb.ErrOutOfOrder)
+				require.ErrorIs(t, err, entrydb.ErrOutOfOrder)
 			})
 	})
 
@@ -266,6 +268,7 @@ func TestAddLog(t *testing.T) {
 				bl14 := eth.BlockID{Hash: createHash(14), Number: 14}
 				err := db.SealBlock(createHash(13), bl14, 5000)
 				require.ErrorIs(t, err, entrydb.ErrConflict)
+				require.ErrorIs(t, err, entrydb.ErrConflict)
 			})
 	})
 
@@ -283,6 +286,7 @@ func TestAddLog(t *testing.T) {
 				onto := eth.BlockID{Hash: createHash(14), Number: 14}
 				err := db.AddLog(createHash(1), onto, 0, nil)
 				require.ErrorIs(t, err, entrydb.ErrOutOfOrder, "cannot build logs on 14 when 15 is already sealed")
+				require.ErrorIs(t, err, entrydb.ErrOutOfOrder, "cannot build logs on 14 when 15 is already sealed")
 			})
 	})
 
@@ -299,6 +303,7 @@ func TestAddLog(t *testing.T) {
 				bl15 := eth.BlockID{Hash: createHash(15), Number: 15}
 				err := db.AddLog(createHash(1), bl15, 0, nil)
 				require.ErrorIs(t, err, entrydb.ErrOutOfOrder, "already at log index 2")
+				require.ErrorIs(t, err, entrydb.ErrOutOfOrder, "already at log index 2")
 			})
 	})
 
@@ -314,6 +319,7 @@ func TestAddLog(t *testing.T) {
 			func(t *testing.T, db *DB, m *stubMetrics) {
 				err := db.AddLog(createHash(1), eth.BlockID{Hash: createHash(16), Number: 16}, 0, nil)
 				require.ErrorIs(t, err, entrydb.ErrOutOfOrder)
+				require.ErrorIs(t, err, entrydb.ErrOutOfOrder)
 			})
 	})
 
@@ -330,6 +336,7 @@ func TestAddLog(t *testing.T) {
 				bl15 := eth.BlockID{Hash: createHash(15), Number: 15}
 				err := db.AddLog(createHash(1), bl15, 1, nil)
 				require.ErrorIs(t, err, entrydb.ErrOutOfOrder, "already at log index 2")
+				require.ErrorIs(t, err, entrydb.ErrOutOfOrder, "already at log index 2")
 			})
 	})
 
@@ -346,6 +353,7 @@ func TestAddLog(t *testing.T) {
 				bl15 := eth.BlockID{Hash: createHash(16), Number: 16}
 				err := db.AddLog(createHash(1), bl15, 2, nil)
 				require.ErrorIs(t, err, entrydb.ErrOutOfOrder)
+				require.ErrorIs(t, err, entrydb.ErrOutOfOrder)
 			})
 	})
 
@@ -361,6 +369,7 @@ func TestAddLog(t *testing.T) {
 				bl15 := eth.BlockID{Hash: createHash(15), Number: 15}
 				err := db.AddLog(createHash(1), bl15, 2, nil)
 				require.ErrorIs(t, err, entrydb.ErrOutOfOrder)
+				require.ErrorIs(t, err, entrydb.ErrOutOfOrder)
 			})
 	})
 
@@ -374,6 +383,7 @@ func TestAddLog(t *testing.T) {
 				bl15 := eth.BlockID{Hash: createHash(15), Number: 15}
 				err := db.AddLog(createHash(1), bl15, 5, nil)
 				require.ErrorIs(t, err, entrydb.ErrOutOfOrder)
+				require.ErrorIs(t, err, entrydb.ErrOutOfOrder)
 			})
 	})
 
@@ -395,6 +405,7 @@ func TestAddLog(t *testing.T) {
 				require.NoError(t, err)
 				err = db.AddLog(createHash(1), bl16, 1, nil)
 				require.ErrorIs(t, err, entrydb.ErrOutOfOrder)
+				require.ErrorIs(t, err, entrydb.ErrOutOfOrder)
 			})
 	})
 
@@ -700,6 +711,8 @@ func TestGetBlockInfo(t *testing.T) {
 			func(t *testing.T, db *DB, m *stubMetrics) {
 				_, err := db.FindSealedBlock(10)
 				require.ErrorIs(t, err, entrydb.ErrFuture)
+				_, err = db.FindSealedBlock(10)
+				require.ErrorIs(t, err, entrydb.ErrFuture)
 			})
 	})
 
@@ -715,6 +728,8 @@ func TestGetBlockInfo(t *testing.T) {
 				// if the DB starts at 11, then shouldn't find 10
 				_, err := db.FindSealedBlock(10)
 				require.ErrorIs(t, err, entrydb.ErrSkipped)
+				_, err = db.FindSealedBlock(10)
+				require.ErrorIs(t, err, entrydb.ErrSkipped)
 			})
 	})
 
@@ -725,10 +740,14 @@ func TestGetBlockInfo(t *testing.T) {
 				require.NoError(t, db.SealBlock(common.Hash{}, block, 500))
 			},
 			func(t *testing.T, db *DB, m *stubMetrics) {
+				_, err := db.FindSealedBlock(block.Number)
+				require.NoError(t, err)
 				seal, err := db.FindSealedBlock(block.Number)
 				require.NoError(t, err)
 				require.Equal(t, block, seal.ID())
 				require.Equal(t, uint64(500), seal.Timestamp)
+				require.Equal(t, block, seal.ID())
+				require.Equal(t, uint64(500), seal.Timestamp)
 			})
 	})
 }
@@ -754,6 +773,7 @@ func requireConflicts(t *testing.T, db *DB, blockNum uint64, logIdx uint32, logH
 	require.True(t, ok, "Did not get the expected metrics type")
 	_, err := db.Contains(blockNum, logIdx, logHash)
 	require.ErrorIs(t, err, entrydb.ErrConflict, "canonical chain must not include this log")
+	require.ErrorIs(t, err, entrydb.ErrConflict, "canonical chain must not include this log")
 	require.LessOrEqual(t, m.entriesReadForSearch, int64(searchCheckpointFrequency*2), "Should not need to read more than between two checkpoints")
 }
 
@@ -762,6 +782,7 @@ func requireFuture(t *testing.T, db *DB, blockNum uint64, logIdx uint32, logHash
 	require.True(t, ok, "Did not get the expected metrics type")
 	_, err := db.Contains(blockNum, logIdx, logHash)
 	require.ErrorIs(t, err, entrydb.ErrFuture, "canonical chain does not yet include this log")
+	require.ErrorIs(t, err, entrydb.ErrFuture, "canonical chain does not yet include this log")
 	require.LessOrEqual(t, m.entriesReadForSearch, int64(searchCheckpointFrequency*2), "Should not need to read more than between two checkpoints")
 }
 
@@ -782,16 +803,16 @@ func requireExecutingMessage(t *testing.T, db *DB, blockNum uint64, logIdx uint3
 }
 
 func TestRecoverOnCreate(t *testing.T) {
-	createDb := func(t *testing.T, store *stubEntryStore) (*DB, *stubMetrics, error) {
+	createDb := func(t *testing.T, store *entrydb.MemEntryStore[EntryType, Entry]) (*DB, *stubMetrics, error) {
 		logger := testlog.Logger(t, log.LvlInfo)
 		m := &stubMetrics{}
 		db, err := NewFromEntryStore(logger, m, store, true)
 		return db, m, err
 	}
 
-	storeWithEvents := func(evts ...Entry) *stubEntryStore {
-		store := &stubEntryStore{}
-		store.entries = append(store.entries, evts...)
+	storeWithEvents := func(evts ...Entry) *entrydb.MemEntryStore[EntryType, Entry] {
+		store := &entrydb.MemEntryStore[EntryType, Entry]{}
+		_ = store.Append(evts...)
 		return store
 	}
 	t.Run("NoTruncateWhenLastEntryIsLogWithNoExecMessageSealed", func(t *testing.T) {
@@ -922,9 +943,11 @@ func TestRewind(t *testing.T) {
 	t.Run("WhenEmpty", func(t *testing.T) {
 		runDBTest(t, func(t *testing.T, db *DB, m *stubMetrics) {},
 			func(t *testing.T, db *DB, m *stubMetrics) {
+				require.ErrorIs(t, db.Rewind(100), entrydb.ErrFuture)
 				require.ErrorIs(t, db.Rewind(100), entrydb.ErrFuture)
 				// Genesis is a block to, not present in an empty DB
 				require.ErrorIs(t, db.Rewind(0), entrydb.ErrFuture)
+				require.ErrorIs(t, db.Rewind(0), entrydb.ErrFuture)
 			})
 	})
 
@@ -943,6 +966,7 @@ func TestRewind(t *testing.T) {
 				require.NoError(t, db.AddLog(createHash(4), bl52, 0, nil))
 				// cannot rewind to a block that is not sealed yet
 				require.ErrorIs(t, db.Rewind(53), entrydb.ErrFuture)
+				require.ErrorIs(t, db.Rewind(53), entrydb.ErrFuture)
 			},
 			func(t *testing.T, db *DB, m *stubMetrics) {
 				requireContains(t, db, 51, 0, createHash(1))
@@ -962,6 +986,7 @@ func TestRewind(t *testing.T) {
 				require.NoError(t, db.AddLog(createHash(2), bl50, 1, nil))
 				// cannot go back to an unknown block
 				require.ErrorIs(t, db.Rewind(25), entrydb.ErrSkipped)
+				require.ErrorIs(t, db.Rewind(25), entrydb.ErrSkipped)
 			},
 			func(t *testing.T, db *DB, m *stubMetrics) {
 				requireContains(t, db, 51, 0, createHash(1))
@@ -1087,11 +1112,13 @@ func TestRewind(t *testing.T) {
 				// 29 was deleted
 				err := db.AddLog(createHash(2), bl29, 1, nil)
 				require.ErrorIs(t, err, entrydb.ErrOutOfOrder, "Cannot add log on removed block")
+				require.ErrorIs(t, err, entrydb.ErrOutOfOrder, "Cannot add log on removed block")
 				// 15 is older, we have up to 16
 				bl15 := eth.BlockID{Hash: createHash(15), Number: 15}
 				// try to add a third log to 15
 				err = db.AddLog(createHash(10), bl15, 2, nil)
 				require.ErrorIs(t, err, entrydb.ErrOutOfOrder)
+				require.ErrorIs(t, err, entrydb.ErrOutOfOrder)
 				bl16 := eth.BlockID{Hash: createHash(16), Number: 16}
 				// try to add a log to 17, on top of 16
 				err = db.AddLog(createHash(42), bl16, 0, nil)
@@ -1116,37 +1143,4 @@ func (s *stubMetrics) RecordDBSearchEntriesRead(count int64) {
 
 var _ Metrics = (*stubMetrics)(nil)
 
-type stubEntryStore struct {
-	entries []Entry
-}
-
-func (s *stubEntryStore) Size() int64 {
-	return int64(len(s.entries))
-}
-
-func (s *stubEntryStore) LastEntryIdx() entrydb.EntryIdx {
-	return entrydb.EntryIdx(s.Size() - 1)
-}
-
-func (s *stubEntryStore) Read(idx entrydb.EntryIdx) (Entry, error) {
-	if idx < entrydb.EntryIdx(len(s.entries)) {
-		return s.entries[idx], nil
-	}
-	return Entry{}, io.EOF
-}
-
-func (s *stubEntryStore) Append(entries ...Entry) error {
-	s.entries = append(s.entries, entries...)
-	return nil
-}
-
-func (s *stubEntryStore) Truncate(idx entrydb.EntryIdx) error {
-	s.entries = s.entries[:min(s.Size()-1, int64(idx+1))]
-	return nil
-}
-
-func (s *stubEntryStore) Close() error {
-	return nil
-}
-
-var _ EntryStore = (*stubEntryStore)(nil)
+var _ entrydb.EntryStore[EntryType, Entry] = (*entrydb.MemEntryStore[EntryType, Entry])(nil)

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

@@ -2,16 +2,35 @@ package logs
 
 import (
 	"fmt"
+	"io"
 	"strings"
-
-	"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/backend/db/entrydb"
 )
 
 type EntryObj interface {
 	encode() Entry
 }
 
-type Entry = entrydb.Entry[EntryType]
+const EntrySize = 34
+
+type Entry [EntrySize]byte
+
+func (e Entry) Type() EntryType {
+	return EntryType(e[0])
+}
+
+type EntryBinary struct{}
+
+func (EntryBinary) Append(dest []byte, e *Entry) []byte {
+	return append(dest, e[:]...)
+}
+
+func (EntryBinary) ReadAt(dest *Entry, r io.ReaderAt, at int64) (n int, err error) {
+	return r.ReadAt(dest[:], at)
+}
+
+func (EntryBinary) EntrySize() int {
+	return EntrySize
+}
 
 type EntryTypeFlag uint8