Added more poison queue context (#170)

message/router/middleware/poison.go

@@ -9,8 +9,13 @@ import (
 // ErrInvalidPoisonQueueTopic occurs when the topic supplied to the PoisonQueue constructor is invalid.
 var ErrInvalidPoisonQueueTopic = errors.New("invalid poison queue topic")
 
-// ReasonForPoisonedKey is the metadata key which marks the reason (error) why the message was deemed poisoned.
-var ReasonForPoisonedKey = "reason_poisoned"
+// Metadata keys which marks the reason and context why the message was deemed poisoned.
+const (
+	ReasonForPoisonedKey  = "reason_poisoned"
+	PoisonedTopicKey      = "topic_poisoned"
+	PoisonedHandlerKey    = "handler_poisoned"
+	PoisonedSubscriberKey = "subscriber_poisoned"
+)
 
 type poisonQueue struct {
 	topic string
@@ -61,6 +66,9 @@ func (pq poisonQueue) publishPoisonMessage(msg *message.Message, err error) erro
 
 	// add context why it was poisoned
 	msg.Metadata.Set(ReasonForPoisonedKey, err.Error())
+	msg.Metadata.Set(PoisonedTopicKey, message.SubscribeTopicFromCtx(msg.Context()))
+	msg.Metadata.Set(PoisonedHandlerKey, message.HandlerNameFromCtx(msg.Context()))
+	msg.Metadata.Set(PoisonedSubscriberKey, message.SubscriberNameFromCtx(msg.Context()))
 
 	// don't intercept error from publish. Can't help you if the publisher is down as well.
 	return pq.pub.Publish(pq.topic, msg)

message/router/middleware/poison_test.go

@@ -1,7 +1,12 @@
 package middleware_test
 
 import (
+	"context"
+	"github.com/ThreeDotsLabs/watermill"
+	"github.com/ThreeDotsLabs/watermill/message/subscriber"
+	"github.com/ThreeDotsLabs/watermill/pubsub/gochannel"
 	"testing"
+	"time"
 
 	"github.com/hashicorp/go-multierror"
 
@@ -106,6 +111,53 @@ func TestPoisonQueue_handler_failing(t *testing.T) {
 	}
 }
 
+func TestPoisonQueue_context_values(t *testing.T) {
+	pubSub := gochannel.NewGoChannel(
+		gochannel.Config{Persistent: true},
+		watermill.NewStdLogger(true, true),
+	)
+
+	logger := watermill.NewStdLogger(true, true)
+
+	router, err := message.NewRouter(message.RouterConfig{}, logger)
+	require.NoError(t, err)
+
+	pq, err := middleware.PoisonQueue(pubSub, "poison_queue")
+	require.NoError(t, err)
+	router.AddMiddleware(pq)
+
+	router.AddNoPublisherHandler("handler_name", "test", pubSub, func(msg *message.Message) error {
+		return errors.New("error")
+	})
+
+	go func() {
+		require.NoError(t, router.Run(context.Background()))
+	}()
+	require.NoError(t, err)
+	defer router.Close()
+
+	select {
+	case <-router.Running():
+	// ok
+	case <-time.After(time.Second):
+		t.Fatal("waiting for router timeout")
+	}
+
+	err = pubSub.Publish("test", message.NewMessage("1", nil))
+	require.NoError(t, err)
+
+	msgs, err := pubSub.Subscribe(context.Background(), "poison_queue")
+	require.NoError(t, err)
+
+	messages, all := subscriber.BulkRead(msgs, 1, time.Second)
+	require.True(t, all, "no messages received")
+
+	assert.Equal(t, "handler_name", messages[0].Metadata[middleware.PoisonedHandlerKey])
+	assert.Equal(t, "gochannel.GoChannel", messages[0].Metadata[middleware.PoisonedSubscriberKey])
+	assert.Equal(t, "test", messages[0].Metadata[middleware.PoisonedTopicKey])
+	assert.Equal(t, "error", messages[0].Metadata[middleware.ReasonForPoisonedKey])
+}
+
 func TestPoisonQueue_handler_failing_publisher_failing(t *testing.T) {
 	poisonPublisher := mockPublisher{behaviour: BehaviourAlwaysFail}