RabbitMQ and channels Java thread safety

Question

in this guide https://www.rabbitmq.com/api-guide.html RabbitMQ guys state:

Channels and Concurrency Considerations (Thread Safety)

Channel instanc

Answer 1

I suppose you are using Channel only for your consumer and not for other operations like publish etc..

In your case the only potential problem is here:

channel.basicAck(deliveryTag, false);

because you call this across two thread, btw this operation is safe, if you see the java code:

the class ChannelN.java calls:

public void basicAck(long deliveryTag, boolean multiple)
   throws IOException
{
   transmit(new Basic.Ack(deliveryTag, multiple));
}

see github code for ChannelN.java

the transmit method inside AMQChannel uses:

public void transmit(Method m) throws IOException {
   synchronized (_channelMutex) {
       transmit(new AMQCommand(m));
   }
}

_channelMutex is a protected final Object _channelMutex = new Object();

created with the class. see github code for AMQChannel.java

EDIT

As you can read on the official documentation, "some" operations are thread-safe, now it is not clear which ones. I studied the code, an I think there are not problems to call the ACK across more threads.

Hope it helps.

EDIT2 I add also Nicolas's comment:

Note that consuming (basicConsume) and acking from more than one thread is a common rabbitmq pattern that is already used by the java client.

So you can use it safe.