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.
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JavaScript
Python
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nc, err := nats.Connect("demo.nats.io")
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if err != nil {
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log.Fatal(err)
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}
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defer nc.Close()
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// Sync Subscription
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sub, err := nc.SubscribeSync("updates")
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if err != nil {
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log.Fatal(err)
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}
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if err := sub.Unsubscribe(); err != nil {
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log.Fatal(err)
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}
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// Async Subscription
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sub, err = nc.Subscribe("updates", func(_ *nats.Msg) {})
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if err != nil {
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log.Fatal(err)
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}
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if err := sub.Unsubscribe(); err != nil {
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log.Fatal(err)
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}
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Connection nc = Nats.connect("nats://demo.nats.io:4222");
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Dispatcher d = nc.createDispatcher((msg) -> {
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String str = new String(msg.getData(), StandardCharsets.UTF_8);
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System.out.println(str);
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});
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// Sync Subscription
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Subscription sub = nc.subscribe("updates");
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sub.unsubscribe();
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// Async Subscription
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d.subscribe("updates");
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d.unsubscribe("updates");
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// Close the connection
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nc.close();
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const sc = StringCodec();
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// set up a subscription to process a request
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const sub = nc.subscribe(createInbox(), (_err, m) => {
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m.respond(sc.encode(new Date().toLocaleTimeString()));
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});
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// without arguments the subscription will cancel when the server receives it
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// you can also specify how many messages are expected by the subscription
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sub.unsubscribe();
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nc = NATS()
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await nc.connect(servers=["nats://demo.nats.io:4222"])
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future = asyncio.Future()
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async def cb(msg):
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nonlocal future
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future.set_result(msg)
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sid = await nc.subscribe("updates", cb=cb)
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await nc.publish("updates", b'All is Well')
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# Remove interest in subject
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await nc.unsubscribe(sid)
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# Won't be received...
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await nc.publish("updates", b'...')
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require 'nats/client'
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require 'fiber'
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NATS.start(servers:["nats://127.0.0.1:4222"]) do |nc|
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Fiber.new do
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f = Fiber.current
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sid = nc.subscribe("time") do |msg, reply|
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f.resume Time.now
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end
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nc.publish("time", 'What is the time?', NATS.create_inbox)
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# Use the response
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msg = Fiber.yield
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puts "Reply: #{msg}"
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nc.unsubscribe(sid)
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# Won't be received
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nc.publish("time", 'What is the time?', NATS.create_inbox)
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end.resume
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end
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natsConnection *conn = NULL;
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natsSubscription *sub = NULL;
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natsStatus s = NATS_OK;
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s = natsConnection_ConnectTo(&conn, NATS_DEFAULT_URL);
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// Subscribe
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if (s == NATS_OK)
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s = natsConnection_SubscribeSync(&sub, conn, "updates");
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// Unsubscribe
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if (s == NATS_OK)
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s = natsSubscription_Unsubscribe(sub);
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(...)
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// Destroy objects that were created
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natsSubscription_Destroy(sub);
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natsConnection_Destroy(conn);
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