zmq4: add option for automatic reconnect

options.go

@@ -51,6 +51,14 @@ func WithLogger(msg *log.Logger) Option {
 	}
 }
 
+// WithAutomaticReconnect allows to configure a socket to automatically
+// reconnect on connection loss.
+func WithAutomaticReconnect(automaticReconnect bool) Option {
+	return func(s *socket) {
+		s.autoReconnect = automaticReconnect
+	}
+}
+
 /*
 // TODO(sbinet)
 

socket.go

@@ -30,13 +30,14 @@ var (
 
 // socket implements the ZeroMQ socket interface
 type socket struct {
-	ep        string // socket end-point
-	typ       SocketType
-	id        SocketIdentity
-	retry     time.Duration
-	sec       Security
-	log       *log.Logger
-	subTopics func() []string
+	ep            string // socket end-point
+	typ           SocketType
+	id            SocketIdentity
+	retry         time.Duration
+	sec           Security
+	log           *log.Logger
+	subTopics     func() []string
+	autoReconnect bool
 
 	mu    sync.RWMutex
 	ids   map[string]*Conn // ZMTP connection IDs
@@ -51,8 +52,9 @@ type socket struct {
 	listener net.Listener
 	dialer   net.Dialer
 
-	closedConns []*Conn
-	reaperCond  *sync.Cond
+	closedConns   []*Conn
+	reaperCond    *sync.Cond
+	reaperStarted bool
 }
 
 func newDefaultSocket(ctx context.Context, sockType SocketType) *socket {
@@ -267,7 +269,10 @@ connect:
 		return fmt.Errorf("zmq4: got a nil ZMTP connection to %q", endpoint)
 	}
 
-	go sck.connReaper()
+	if !sck.reaperStarted {
+		go sck.connReaper()
+		sck.reaperStarted = true
+	}
 	sck.addConn(zconn)
 	return nil
 }
@@ -326,6 +331,10 @@ func (sck *socket) scheduleRmConn(c *Conn) {
 	sck.closedConns = append(sck.closedConns, c)
 	sck.reaperCond.Signal()
 	sck.reaperCond.L.Unlock()
+
+	if sck.autoReconnect {
+		sck.Dial(sck.ep)
+	}
 }
 
 // Type returns the type of this Socket (PUB, SUB, ...)

socket_test.go

@@ -6,6 +6,7 @@ package zmq4_test
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"io"
 	"net"
@@ -260,3 +261,68 @@ func TestSocketSendSubscriptionOnConnect(t *testing.T) {
 		t.Fatalf("invalid message received: got '%s', wanted '%s'", msg.Frames[0], message)
 	}
 }
+
+func TestSocketAutomaticReconnect(t *testing.T) {
+	listenEndpoint := "tcp://*:1234"
+	dialEndpoint := "tcp://localhost:1234"
+	message := "test"
+
+	ctx, cancel := context.WithCancel(context.Background())
+
+	wg := new(sync.WaitGroup)
+	defer wg.Wait()
+	defer cancel()
+	sendMessages := func(socket zmq4.Socket) {
+		wg.Add(1)
+		go func(t *testing.T) {
+			defer wg.Done()
+			for {
+				socket.Send(zmq4.NewMsgFromString([]string{message}))
+				if ctx.Err() != nil {
+					return
+				}
+				time.Sleep(1 * time.Millisecond)
+			}
+		}(t)
+	}
+
+	sub := zmq4.NewSub(context.Background(), zmq4.WithAutomaticReconnect(true))
+	defer sub.Close()
+	sub.SetOption(zmq4.OptionSubscribe, message)
+	pub := zmq4.NewPub(context.Background())
+	if err := pub.Listen(dialEndpoint); err != nil {
+		t.Fatalf("Pub Dial failed: %v", err)
+	}
+	if err := sub.Dial(listenEndpoint); err != nil {
+		t.Fatalf("Sub Dial failed: %v", err)
+	}
+
+	sendMessages(pub)
+
+	checkConnectionWorking := func(socket zmq4.Socket) {
+		for {
+			msg, err := socket.Recv()
+			if errors.Is(err, io.EOF) {
+				continue
+			}
+			if err != nil {
+				t.Fatalf("Recv failed: %v", err)
+			}
+			if string(msg.Frames[0]) != message {
+				t.Fatalf("invalid message received: got '%s', wanted '%s'", msg.Frames[0], message)
+			}
+			return
+		}
+	}
+
+	checkConnectionWorking(sub)
+	pub.Close()
+
+	pub2 := zmq4.NewPub(context.Background())
+	defer pub2.Close()
+	if err := pub2.Listen(listenEndpoint); err != nil {
+		t.Fatalf("Sub Listen failed: %v", err)
+	}
+	sendMessages(pub2)
+	checkConnectionWorking(sub)
+}