In my previous post I wrote about ServiceProxy and how easy it should be to integrate with messaging frameworks and do request/reply with service contracts even if your messaging framework has no support for it.
If you’re not familiar with Redis, you should take some time and get acquainted with it. There is a lot of material on Redis website to get you started, and you’ll be amazed with how Redis helps you solve complex problems in a simple, easy and performant way. There are many use cases for Redis, and one is certainly messaging. Redis supports queues and pub/sub, which are the messaging capabilities that probably most common systems will ever need.
Request-Reply can be done with Redis in many ways: queues with or without blocking primitives, pub/sub or a combination of pub/sub and queues.
ServiceProxy.Redis uses an asynchronous and reliable request-reply pattern using Queues. There are two ways of dequeuing items in Redis: non-blocking and blocking. The non-blocking operation returns immediately whether there is an item to be dequeued or not, returning null in the latter. The blocking operation is used together with a timeout parameter and Redis will block the client’s connection when the queue is empty, until an item can be dequeued or the timeout time is reached. When multiple connections are blocked on the same queue, Redis will do fair queueing among them, so load balancing is trivially simple to do. Since the connection to Redis can be blocked when dequeuing, it is recommended to use a different connection for enqueuing and/or issueing other non-blocking commands. The same principle applies when doing pubsub (one connection to subscribe channels, another to publish and/or issue other commands).