Unsubscribing

The client libraries provide a means to unsubscribe a previous subscription request.

This process requires an interaction with the server, so for an asynchronous subscription there may be a small window of time where a message comes through as the unsubscribe is processed by the library. Ignoring that slight edge case, the client library will clean up any outstanding messages and tell the server that the subscription is no longer used.

Go

  1. nc, err := nats.Connect("demo.nats.io")
  2. if err != nil {
  3.     log.Fatal(err)
  4. }
  5. defer nc.Close()
  7. // Sync Subscription
  8. sub, err := nc.SubscribeSync("updates")
  9. if err != nil {
  10.     log.Fatal(err)
  11. }
  12. if err := sub.Unsubscribe(); err != nil {
  13.     log.Fatal(err)
  14. }
  16. // Async Subscription
  17. sub, err = nc.Subscribe("updates", func(_ *nats.Msg) {})
  18. if err != nil {
  19.     log.Fatal(err)
  20. }
  21. if err := sub.Unsubscribe(); err != nil {
  22.     log.Fatal(err)
  23. }

Java

  1. Connection nc = Nats.connect("nats://demo.nats.io:4222");
  2. Dispatcher d = nc.createDispatcher((msg) -> {
  3.     String str = new String(msg.getData(), StandardCharsets.UTF_8);
  4.     System.out.println(str);
  5. });
  7. // Sync Subscription
  8. Subscription sub = nc.subscribe("updates");
  9. sub.unsubscribe();
  11. // Async Subscription
  12. d.subscribe("updates");
  13. d.unsubscribe("updates");
  15. // Close the connection
  16. nc.close();

JavaScript

  1. const sc = StringCodec();
  2. // set up a subscription to process a request
  3. const sub = nc.subscribe(createInbox(), (_err, m) => {
  4.   m.respond(sc.encode(new Date().toLocaleTimeString()));
  5. });
  6. // without arguments the subscription will cancel when the server receives it
  7. // you can also specify how many messages are expected by the subscription
  8. sub.unsubscribe();

Python

  1. nc = NATS()
  3. await nc.connect(servers=["nats://demo.nats.io:4222"])
  5. future = asyncio.Future()
  7. async def cb(msg):
  8.   nonlocal future
  9.   future.set_result(msg)
  11. sid = await nc.subscribe("updates", cb=cb)
  12. await nc.publish("updates", b'All is Well')
  14. # Remove interest in subject
  15. await nc.unsubscribe(sid)
  17. # Won't be received...
  18. await nc.publish("updates", b'...')

Ruby

  1. require 'nats/client'
  2. require 'fiber'
  4. NATS.start(servers:["nats://127.0.0.1:4222"]) do |nc|
  5.   Fiber.new do
  6.     f = Fiber.current
  8.     sid = nc.subscribe("time") do |msg, reply|
  9.       f.resume Time.now
  10.     end
  12.     nc.publish("time", 'What is the time?', NATS.create_inbox)
  14.     # Use the response
  15.     msg = Fiber.yield
  16.     puts "Reply: #{msg}"
  18.     nc.unsubscribe(sid)
  20.     # Won't be received
  21.     nc.publish("time", 'What is the time?', NATS.create_inbox)
  23.   end.resume
  24. end

C

  1. natsConnection      *conn      = NULL;
  2. natsSubscription    *sub       = NULL;
  3. natsStatus          s          = NATS_OK;
  5. s = natsConnection_ConnectTo(&conn, NATS_DEFAULT_URL);
  7. // Subscribe
  8. if (s == NATS_OK)
  9.     s = natsConnection_SubscribeSync(&sub, conn, "updates");
  11. // Unsubscribe
  12. if (s == NATS_OK)
  13.     s = natsSubscription_Unsubscribe(sub);
  15. (...)
  17. // Destroy objects that were created
  18. natsSubscription_Destroy(sub);
  19. natsConnection_Destroy(conn);

{% endtabs %}