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Update queues.md

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Ginger Collison 2019-10-07 11:04:29 -05:00 committed by GitHub
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@ -8,7 +8,118 @@ Keep in mind that the queue groups in NATS are dynamic and do not require any se
As an example, to subscribe to the queue `workers` with the subject `updates`:
!INCLUDE "../../\_examples/subscribe\_queue.html"
{% tabs %}
{% tab title="Go" %}
```go
nc, err := nats.Connect("demo.nats.io")
if err != nil {
log.Fatal(err)
}
defer nc.Close()
// Use a WaitGroup to wait for 10 messages to arrive
wg := sync.WaitGroup{}
wg.Add(10)
// Create a queue subscription on "updates" with queue name "workers"
if _, err := nc.QueueSubscribe("updates", "worker", func(m *nats.Msg) {
wg.Done()
}); err != nil {
log.Fatal(err)
}
// Wait for messages to come in
wg.Wait()
```
{% endtab %}
{% tab title="Java" %}
```java
Connection nc = Nats.connect("nats://demo.nats.io:4222");
// Use a latch to wait for 10 messages to arrive
CountDownLatch latch = new CountDownLatch(10);
// Create a dispatcher and inline message handler
Dispatcher d = nc.createDispatcher((msg) -> {
String str = new String(msg.getData(), StandardCharsets.UTF_8);
System.out.println(str);
latch.countDown();
});
// Subscribe
d.subscribe("updates", "workers");
// Wait for a message to come in
latch.await();
// Close the connection
nc.close();
```
{% endtab %}
{% tab title="JavaScript" %}
```javascript
let nc = NATS.connect({
url: "nats://demo.nats.io:4222"});
nc.subscribe('updates', {queue: "workers"}, (msg) => {
t.log('worker got message', msg);
});
```
{% endtab %}
{% tab title="Python" %}
```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)
await nc.subscribe("updates", queue="workers", cb=cb)
await nc.publish("updates", b'All is Well')
msg = await asyncio.wait_for(future, 1)
print("Msg", msg)
```
{% endtab %}
{% tab title="Ruby" %}
```ruby
require 'nats/client'
require 'fiber'
NATS.start(servers:["nats://127.0.0.1:4222"]) do |nc|
Fiber.new do
f = Fiber.current
nc.subscribe("updates", queue: "worker") do |msg, reply|
f.resume Time.now
end
nc.publish("updates", "A")
# Use the response
msg = Fiber.yield
puts "Msg: #{msg}"
end.resume
end
```
{% endtab %}
{% tab title="TypeScript" %}
```typescript
await nc.subscribe('updates', (err, msg) => {
t.log('worker got message', msg.data);
}, {queue: "workers"});
```
{% endtab %}
{% endtabs %}
If you run this example with the publish examples that send to `updates`, you will see that one of the instances gets a message while the others you run won't. But the instance that receives the message will change.