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
Java
JavaScript
Python
Ruby
TypeScript
C
Go
nc, err := nats.Connect("demo.nats.io")
if err != nil {
log.Fatal(err)
}
defer nc.Close()
// Sync Subscription
sub, err := nc.SubscribeSync("updates")
if err != nil {
log.Fatal(err)
}
if err := sub.Unsubscribe(); err != nil {
log.Fatal(err)
}
// Async Subscription
sub, err = nc.Subscribe("updates", func(_ *nats.Msg) {})
if err != nil {
log.Fatal(err)
}
if err := sub.Unsubscribe(); err != nil {
log.Fatal(err)
}
Java
Connection nc = Nats.connect("nats://demo.nats.io:4222");
Dispatcher d = nc.createDispatcher((msg) -> {
String str = new String(msg.getData(), StandardCharsets.UTF_8);
System.out.println(str);
});
// Sync Subscription
Subscription sub = nc.subscribe("updates");
sub.unsubscribe();
// Async Subscription
d.subscribe("updates");
d.unsubscribe("updates");
// Close the connection
nc.close();
JavaScript
let nc = NATS.connect({
url: "nats://demo.nats.io:4222"
});
// set up a subscription to process a request
let sub = nc.subscribe(NATS.createInbox(), (msg, reply) => {
if (msg.reply) {
nc.publish(reply, new Date().toLocaleTimeString());
}
});
// without arguments the subscription will cancel when the server receives it
// you can also specify how many messages are expected by the subscription
nc.unsubscribe(sub);
Python
nc = NATS()
await nc.connect(servers=["nats://demo.nats.io:4222"])
future = asyncio.Future()
async def cb(msg):
nonlocal future
future.set_result(msg)
sid = await nc.subscribe("updates", cb=cb)
await nc.publish("updates", b'All is Well')
# Remove interest in subject
await nc.unsubscribe(sid)
# Won't be received...
await nc.publish("updates", b'...')
Ruby
require 'nats/client'
require 'fiber'
NATS.start(servers:["nats://127.0.0.1:4222"]) do |nc|
Fiber.new do
f = Fiber.current
sid = nc.subscribe("time") do |msg, reply|
f.resume Time.now
end
nc.publish("time", 'What is the time?', NATS.create_inbox)
# Use the response
msg = Fiber.yield
puts "Reply: #{msg}"
nc.unsubscribe(sid)
# Won't be received
nc.publish("time", 'What is the time?', NATS.create_inbox)
end.resume
end
TypeScript
// set up a subscription to process a request
let sub = await nc.subscribe(createInbox(), (err, msg) => {
if (msg.reply) {
nc.publish(msg.reply, new Date().toLocaleTimeString());
} else {
t.log('got a request for the time, but no reply subject was set.');
}
});
// without arguments the subscription will cancel when the server receives it
// you can also specify how many messages are expected by the subscription
sub.unsubscribe();
C
natsConnection *conn = NULL;
natsSubscription *sub = NULL;
natsStatus s = NATS_OK;
s = natsConnection_ConnectTo(&conn, NATS_DEFAULT_URL);
// Subscribe
if (s == NATS_OK)
s = natsConnection_SubscribeSync(&sub, conn, "updates");
// Unsubscribe
if (s == NATS_OK)
s = natsSubscription_Unsubscribe(sub);
(...)
// Destroy objects that were created
natsSubscription_Destroy(sub);
natsConnection_Destroy(conn);
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