Channels and Concurrency Considerations (Thread Safety)

As a rule of thumb, sharing Channel instances between threads is something to be avoided. Applications should prefer using a Channel per thread instead of sharing the same Channel across multiple threads.

While some operations on channels are safe to invoke concurrently, some are not and will result in incorrect frame interleaving on the wire, double acknowledgements and so on.

Concurrent publishing on a shared channel can result in incorrect frame interleaving on the wire, triggering a connection-level protocol exception and immediate connection closure by the broker. It therefore requires explicit synchronization in application code (Channel#basicPublish must be invoked in a critical section). Sharing channels between threads will also interfere with Publisher Confirms. Concurrent publishing on a shared channel is best avoided entirely, e.g. by using a channel per thread.

It is possible to use channel pooling to avoid concurrent publishing on a shared channel: once a thread is done working with a channel, it returns it to the pool, making the channel available for another thread. Channel pooling can be thought of as a specific synchronization solution. It is recommended that an existing pooling library is used instead of a homegrown solution. For example, Spring AMQP which comes with a ready-to-use channel pooling feature.