MF-1681 - Failed to reconnect to NATS (#1686)

* Make NATS reconnect never give up

Signed-off-by: dusanb94 <dusan.borovcanin@mainflux.com>

* Extract maxReconnects to a constant

Signed-off-by: dusanb94 <dusan.borovcanin@mainflux.com>

Signed-off-by: dusanb94 <dusan.borovcanin@mainflux.com>

docker/brokers/nats.yml

@@ -1,7 +1,7 @@
 services:
   broker:
     image: nats:2.2.4-alpine
-    command: "-c /etc/nats/nats.conf"
+    command: "-c /etc/nats/nats.conf -DV"
     volumes:
       - ./../nats/:/etc/nats
     ports:

pkg/messaging/nats/publisher.go

@@ -11,6 +11,11 @@ import (
 	broker "github.com/nats-io/nats.go"
 )
 
+// A maximum number of reconnect attempts before NATS connection closes permanently.
+// Value -1 represents an unlimited number of reconnect retries, i.e. the client
+// will never give up on retrying to re-establish connection to NATS server.
+const maxReconnects = -1
+
 var _ messaging.Publisher = (*publisher)(nil)
 
 type publisher struct {
@@ -22,7 +27,7 @@ type publisher struct {
 
 // NewPublisher returns NATS message Publisher.
 func NewPublisher(url string) (messaging.Publisher, error) {
-	conn, err := broker.Connect(url)
+	conn, err := broker.Connect(url, broker.MaxReconnects(maxReconnects))
 	if err != nil {
 		return nil, err
 	}

pkg/messaging/nats/pubsub.go

@@ -17,12 +17,11 @@ import (
 
 const chansPrefix = "channels"
 
+// Publisher and Subscriber errors.
 var (
-	ErrAlreadySubscribed = errors.New("already subscribed to topic")
-	ErrNotSubscribed     = errors.New("not subscribed")
-	ErrEmptyTopic        = errors.New("empty topic")
-	ErrEmptyID           = errors.New("empty id")
-	ErrFailed            = errors.New("failed")
+	ErrNotSubscribed = errors.New("not subscribed")
+	ErrEmptyTopic    = errors.New("empty topic")
+	ErrEmptyID       = errors.New("empty id")
 )
 
 var _ messaging.PubSub = (*pubsub)(nil)
@@ -48,7 +47,7 @@ type pubsub struct {
 // here: https://docs.nats.io/developing-with-nats/receiving/queues.
 // If the queue is empty, Subscribe will be used.
 func NewPubSub(url, queue string, logger log.Logger) (messaging.PubSub, error) {
-	conn, err := broker.Connect(url)
+	conn, err := broker.Connect(url, broker.MaxReconnects(maxReconnects))
 	if err != nil {
 		return nil, err
 	}

pkg/messaging/nats/pubsub_test.go

@@ -4,6 +4,7 @@
 package nats_test
 
 import (
+	"errors"
 	"fmt"
 	"testing"
 
@@ -22,8 +23,9 @@ const (
 )
 
 var (
-	msgChan = make(chan messaging.Message)
-	data    = []byte("payload")
+	msgChan   = make(chan messaging.Message)
+	data      = []byte("payload")
+	errFailed = errors.New("failed")
 )
 
 func TestPublisher(t *testing.T) {
@@ -230,7 +232,7 @@ func TestPubsub(t *testing.T) {
 			desc:         "Subscribe to another already subscribed topic with an ID with Unsubscribe failing",
 			topic:        fmt.Sprintf("%s.%s", chansPrefix, topic+"1"),
 			clientID:     "clientid3",
-			errorMessage: nats.ErrFailed,
+			errorMessage: errFailed,
 			pubsub:       true,
 			handler:      handler{true},
 		},
@@ -246,7 +248,7 @@ func TestPubsub(t *testing.T) {
 			desc:         "Unsubscribe from a topic with an ID with failing handler",
 			topic:        fmt.Sprintf("%s.%s", chansPrefix, topic+"2"),
 			clientID:     "clientid4",
-			errorMessage: nats.ErrFailed,
+			errorMessage: errFailed,
 			pubsub:       false,
 			handler:      handler{true},
 		},
@@ -282,7 +284,7 @@ func (h handler) Handle(msg messaging.Message) error {
 
 func (h handler) Cancel() error {
 	if h.fail {
-		return nats.ErrFailed
+		return errFailed
 	}
 	return nil
 }