core/rawdb, ethdb, trie: implement db.Sync

core/rawdb/table.go

@@ -188,6 +188,12 @@ func (t *table) Compact(start []byte, limit []byte) error {
 	return t.db.Compact(start, limit)
 }
 
+// Sync ensures that all pending writes are flushed to disk, guaranteeing
+// data durability up to the point.
+func (t *table) Sync() error {
+	return t.db.Sync()
+}
+
 // NewBatch creates a write-only database that buffers changes to its host db
 // until a final write is called, each operation prefixing all keys with the
 // pre-configured string.

ethdb/database.go

@@ -57,6 +57,13 @@ type KeyValueStater interface {
 	Stat() (string, error)
 }
 
+// KeyValueSyncer wraps the Sync method of a backing data store.
+type KeyValueSyncer interface {
+	// Sync ensures that all pending writes are flushed to disk, guaranteeing
+	// data durability up to the point.
+	Sync() error
+}
+
 // Compacter wraps the Compact method of a backing data store.
 type Compacter interface {
 	// Compact flattens the underlying data store for the given key range. In essence,
@@ -75,6 +82,7 @@ type KeyValueStore interface {
 	KeyValueReader
 	KeyValueWriter
 	KeyValueStater
+	KeyValueSyncer
 	KeyValueRangeDeleter
 	Batcher
 	Iteratee

ethdb/leveldb/leveldb.go

@@ -324,6 +324,12 @@ func (db *Database) Path() string {
 	return db.fn
 }
 
+// Sync flushes all pending writes in the write-ahead-log to disk, ensuring
+// data durability up to that point.
+func (db *Database) Sync() error {
+	return nil
+}
+
 // meter periodically retrieves internal leveldb counters and reports them to
 // the metrics subsystem.
 func (db *Database) meter(refresh time.Duration, namespace string) {

ethdb/memorydb/memorydb.go

@@ -199,6 +199,12 @@ func (db *Database) Compact(start []byte, limit []byte) error {
 	return nil
 }
 
+// Sync ensures that all pending writes are flushed to disk, guaranteeing
+// data durability up to the point.
+func (db *Database) Sync() error {
+	return nil
+}
+
 // Len returns the number of entries currently present in the memory database.
 //
 // Note, this method is only used for testing (i.e. not public in general) and

ethdb/pebble/pebble.go

@@ -414,6 +414,14 @@ func (d *Database) Path() string {
 	return d.fn
 }
 
+// Sync flushes all pending writes in the write-ahead-log to disk, ensuring
+// data durability up to that point.
+func (d *Database) Sync() error {
+	b := d.db.NewBatch()
+	b.LogData(nil, nil)
+	return d.db.Apply(b, pebble.Sync)
+}
+
 // meter periodically retrieves internal pebble counters and reports them to
 // the metrics subsystem.
 func (d *Database) meter(refresh time.Duration, namespace string) {

ethdb/remotedb/remotedb.go

@@ -138,6 +138,10 @@ func (db *Database) Compact(start []byte, limit []byte) error {
 	return nil
 }
 
+func (db *Database) Sync() error {
+	return nil
+}
+
 func (db *Database) Close() error {
 	db.remote.Close()
 	return nil

trie/trie_test.go

@@ -830,6 +830,7 @@ func (s *spongeDb) NewBatch() ethdb.Batch                    { return &spongeBat
 func (s *spongeDb) NewBatchWithSize(size int) ethdb.Batch    { return &spongeBatch{s} }
 func (s *spongeDb) Stat() (string, error)                    { panic("implement me") }
 func (s *spongeDb) Compact(start []byte, limit []byte) error { panic("implement me") }
+func (s *spongeDb) Sync() error                              { return nil }
 func (s *spongeDb) Close() error                             { return nil }
 func (s *spongeDb) Put(key []byte, value []byte) error {
 	var (