Request/Reply patterns

One-way communications can give us great advantages in terms of parallelism and efficiency, but alone they are not able to solve all our integration and communication problems. Sometimes, a good old request/reply pattern might just be the perfect tool for the job. But, there are situations in which all we have is an asynchronous one-way channel. It's therefore important to know the various patterns and approaches required to build an abstraction that would allow us to exchange messages in a request/reply fashion on top of a one-way channel. That's exactly what we are going to learn next.

Correlation Identifier

The first Request/Reply pattern that we are going to learn is called the Correlation Identifier and it represents the basic block for building a request/reply abstraction on top of a one-way channel.

The pattern involves marking each request with an identifier, which is then attached to the response...