metrics

pkg/actor/state.go

@@ -12,6 +12,12 @@ import (
 
 type StateStorage struct {
 	registry MutationRegistry
+	// metrics is set by the owning DiskStorage via SetMetrics. Nil is fine —
+	// every method that touches it nil-checks first. The pointer is
+	// intentionally unexported: callers set it through DiskStorage.SetMetrics
+	// so the embedded StateStorage always tracks the parent disk storage's
+	// metrics, even if the embedded value is replaced.
+	metrics *Metrics
 }
 
 type StorageEvent struct {
@@ -50,10 +56,20 @@ func (s *StateStorage) Load(r io.Reader, onMessage func(msg proto.Message, timeS
 	return err
 }
 
-func (s *StateStorage) Append(io io.Writer, mutation proto.Message, timeStamp time.Time) error {
+// Append serialises a mutation as a StorageEvent and writes it (plus a
+// trailing newline) to io. The first return value is the number of
+// bytes written, which the caller (DiskStorage) adds to the
+// event_log_bytes_written_total counter; the second is the underlying
+// write error, if any. ErrUnknownType is returned (with 0 bytes) when
+// the mutation's type is not registered, and is also counted in
+// event_log_unknown_types_total.
+func (s *StateStorage) Append(io io.Writer, mutation proto.Message, timeStamp time.Time) (int, error) {
 	typeName, ok := s.registry.GetTypeName(mutation)
 	if !ok {
-		return ErrUnknownType
+		if s.metrics != nil {
+			s.metrics.EventLogUnknownTypes.Inc()
+		}
+		return 0, ErrUnknownType
 	}
 	event := &StorageEvent{
 		Type:      typeName,
@@ -62,13 +78,16 @@ func (s *StateStorage) Append(io io.Writer, mutation proto.Message, timeStamp ti
 	}
 	jsonBytes, err := json.Marshal(event)
 	if err != nil {
-		return err
+		return 0, err
 	}
-	if _, err := io.Write(jsonBytes); err != nil {
-		return err
+	n, err := io.Write(jsonBytes)
+	total := n
+	if err != nil {
+		return total, err
 	}
-	io.Write([]byte("\n"))
-	return nil
+	n, err = io.Write([]byte("\n"))
+	total += n
+	return total, err
 }
 
 func (s *StateStorage) Read(r *bufio.Scanner) (*StorageEvent, error) {
@@ -83,6 +102,9 @@ func (s *StateStorage) Read(r *bufio.Scanner) (*StorageEvent, error) {
 		typeName := event.Type
 		mutation, ok := s.registry.Create(typeName)
 		if !ok {
+			if s.metrics != nil {
+				s.metrics.EventLogUnknownTypes.Inc()
+			}
 			return nil, ErrUnknownType
 		}
 		if err := json.Unmarshal(event.Mutation, mutation); err != nil {