[WIP]: broker ErrorHandler option (#1296)

* broker ErrorHandler option

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* rewrite Event interface, add error

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* implement new interface

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* change ErrorHandler func to broker.Handler

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* fix

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

broker/broker.go

@@ -28,6 +28,7 @@ type Event interface {
 	Topic() string
 	Message() *Message
 	Ack() error
+	Error() error
 }
 
 // Subscriber is a convenience return type for the Subscribe method

broker/default.go

@@ -54,6 +54,7 @@ type subscriber struct {
 
 type publication struct {
 	t   string
+	err error
 	m   *Message
 }
 
@@ -70,6 +71,10 @@ func (p *publication) Ack() error {
 	return nil
 }
 
+func (p *publication) Error() error {
+	return p.err
+}
+
 func (s *subscriber) Options() SubscribeOptions {
 	return s.opts
 }
@@ -390,10 +395,26 @@ func (n *natsBroker) Subscribe(topic string, handler Handler, opts ...SubscribeO
 
 	fn := func(msg *nats.Msg) {
 		var m Message
-		if err := n.opts.Codec.Unmarshal(msg.Data, &m); err != nil {
+		pub := &publication{t: msg.Subject}
+		eh := n.opts.ErrorHandler
+		err := n.opts.Codec.Unmarshal(msg.Data, &m)
+		pub.err = err
+		pub.m = &m
+		if err != nil {
+			m.Body = msg.Data
+			log.Error(err)
+			if eh != nil {
+				eh(pub)
+			}
 			return
 		}
-		handler(&publication{m: &m, t: msg.Subject})
+		if err := handler(pub); err != nil {
+			pub.err = err
+			log.Error(err)
+			if eh != nil {
+				eh(pub)
+			}
+		}
 	}
 
 	var sub *nats.Subscription

broker/memory/memory.go

@@ -27,6 +27,7 @@ type memoryBroker struct {
 type memoryEvent struct {
 	opts    broker.Options
 	topic   string
+	err     error
 	message interface{}
 }
 
@@ -120,6 +121,11 @@ func (m *memoryBroker) Publish(topic string, msg *broker.Message, opts ...broker
 
 	for _, sub := range subs {
 		if err := sub.handler(p); err != nil {
+			p.err = err
+			if eh := m.opts.ErrorHandler; eh != nil {
+				eh(p)
+				continue
+			}
 			return err
 		}
 	}
@@ -197,6 +203,10 @@ func (m *memoryEvent) Ack() error {
 	return nil
 }
 
+func (m *memoryEvent) Error() error {
+	return m.err
+}
+
 func (m *memorySubscriber) Options() broker.SubscribeOptions {
 	return m.opts
 }

broker/nats/nats.go

@@ -51,6 +51,7 @@ type subscriber struct {
 
 type publication struct {
 	t   string
+	err error
 	m   *broker.Message
 }
 
@@ -67,6 +68,10 @@ func (p *publication) Ack() error {
 	return nil
 }
 
+func (p *publication) Error() error {
+	return p.err
+}
+
 func (s *subscriber) Options() broker.SubscribeOptions {
 	return s.opts
 }
@@ -375,10 +380,26 @@ func (n *natsBroker) Subscribe(topic string, handler broker.Handler, opts ...bro
 
 	fn := func(msg *nats.Msg) {
 		var m broker.Message
-		if err := n.opts.Codec.Unmarshal(msg.Data, &m); err != nil {
+		pub := &publication{t: msg.Subject}
+		eh := n.opts.ErrorHandler
+		err := n.opts.Codec.Unmarshal(msg.Data, &m)
+		pub.err = err
+		pub.m = &m
+		if err != nil {
+			m.Body = msg.Data
+			log.Error(err)
+			if eh != nil {
+				eh(pub)
+			}
 			return
 		}
-		handler(&publication{m: &m, t: msg.Subject})
+		if err := handler(pub); err != nil {
+			pub.err = err
+			log.Error(err)
+			if eh != nil {
+				eh(pub)
+			}
+		}
 	}
 
 	var sub *nats.Subscription

broker/options.go

@@ -12,6 +12,11 @@ type Options struct {
 	Addrs  []string
 	Secure bool
 	Codec  codec.Marshaler
+
+	// Handler executed when error happens in broker mesage
+	// processing
+	ErrorHandler Handler
+
 	TLSConfig *tls.Config
 	// Registry used for clustering
 	Registry registry.Registry
@@ -81,6 +86,14 @@ func DisableAutoAck() SubscribeOption {
 	}
 }
 
+// ErrorHandler will catch all broker errors that cant be handled
+// in normal way, for example Codec errors
+func ErrorHandler(h Handler) Option {
+	return func(o *Options) {
+		o.ErrorHandler = h
+	}
+}
+
 // Queue sets the name of the queue to share messages on
 func Queue(name string) SubscribeOption {
 	return func(o *SubscribeOptions) {

broker/service/subscriber.go

@@ -17,6 +17,7 @@ type serviceSub struct {
 
 type serviceEvent struct {
 	topic   string
+	err     error
 	message *broker.Message
 }
 
@@ -32,6 +33,10 @@ func (s *serviceEvent) Ack() error {
 	return nil
 }
 
+func (s *serviceEvent) Error() error {
+	return s.err
+}
+
 func (s *serviceSub) isClosed() bool {
 	select {
 	case <-s.closed:
@@ -71,14 +76,14 @@ func (s *serviceSub) run() error {
 			return err
 		}
 
-		// TODO: handle error
-		s.handler(&serviceEvent{
+		p := &serviceEvent{
 			topic: s.topic,
 			message: &broker.Message{
 				Header: msg.Header,
 				Body:   msg.Body,
 			},
-		})
+		}
+		p.err = s.handler(p)
 	}
 }
 

server/rpc_event.go

@@ -7,6 +7,7 @@ import (
 
 // event is a broker event we handle on the server transport
 type event struct {
+	err     error
 	message *broker.Message
 }
 
@@ -19,6 +20,10 @@ func (e *event) Message() *broker.Message {
 	return e.message
 }
 
+func (e *event) Error() error {
+	return e.err
+}
+
 func (e *event) Topic() string {
 	return e.message.Header["Micro-Topic"]
 }

tunnel/broker/broker.go

@@ -163,6 +163,10 @@ func (t *tunEvent) Ack() error {
 	return nil
 }
 
+func (t *tunEvent) Error() error {
+	return nil
+}
+
 func NewBroker(opts ...broker.Option) broker.Broker {
 	options := broker.Options{
 		Context: context.Background(),