RpcClient not thread safe

[karlnicholas]

• RabbitMQ version:
  <groupId>com.rabbitmq</groupId>
<artifactId>amqp-client</artifactId>
<version>5.13.1</version>

• A runnable code sample, terminal transcript or detailed set of
  instructions that can be used to reproduce the issue:
  Make two threads in com.rabbitmq.client.test.RpcTest.java
  e.g. RabbitMQRpcClient

• Operating system, version, and patch level:
  Java 11: Windows 11

• Errors reported in the JavaScript console (if any):

Caused by: com.rabbitmq.client.ShutdownSignalException: channel error; protocol method: #method<channel.close>(reply-code=406, reply-text=PRECONDITION_FAILED - reply consumer already set, class-id=60, method-id=20)

My use case is that I am calling RpcClient from a REST service. When two clients hit the REST endpoint "at the same time" then RpcClient gives the above exception.

[michaelklishin]

Given that most clients, including this one, explicitly do not allow sharing channels across threads, I'm not sure
how much sense it makes to try make it safe.

You are welcome to look into it or simply roll your own. This "RPC client" was developed years ago primarily as an example.

[michaelklishin]

Another issue you will run into is a shared response queue. So you probably want a separate channel per thread (avoiding creating a new one of the fly every time as much as possible) and Direct reply to.