What it is
The request reply pattern lets a caller send a message and receive a matching response over messaging infrastructure. It models a call without coupling the two parties to a shared connection.
How it works
- The requester sends a message to a request channel.
- It includes a reply to address naming where the answer should go.
- It also includes a correlation id so the reply can be matched to the original request.
- The replier processes the request and sends the answer to the reply channel.
Why it matters
- Works across process and network boundaries without tight coupling.
- The reply channel can be temporary per requester or shared with correlation ids.
- The requester may block and wait or handle the reply later, keeping it flexible.
The cost is added latency and the need to track outstanding requests. Without a correlation id, a shared reply channel cannot tell two answers apart.
Key idea
Request reply pairs a request channel with a reply channel, using a correlation id to match each answer to its question.