CODEWITHSUNDEEP
javatomcatrabbitmqrpc
willemsst
willemsst

Reputation: 51

How to setup RabbitMQ RPC in a web context

RabbitMQ RPC

I decided to use RabbitMQ RPC as described here.

My Setup

Incoming web requests (on Tomcat) will dispatch RPC requests over RabbitMQ to different services and assemble the results. I use one reply queue with one custom consumer that listens to all RPC responses and collects them with their correlation id in a simple hash map. Nothing fancy there. This works great in a simple integration test on controller level.

Problem

When I try to do this in a web project deployed on Tomcat, Tomcat refuses to shut down. jstack and some debugging learned me a thread is spawn to listen for the RPC response and is blocking Tomcat from shutting down gracefully. I guess this is because the created thread is created on application level instead of request level and is not managed by Tomcat. When I set breakpoints in Servlet.destroy() or ServletContextListener.contextDestroyed(ServletContextEvent sce), they are not reached, so I see no way to manually clean things up.

Alternative

As an alternative, I could use a new reply queue (and simple QueueingConsumer) for each web request. I've tested this, it works and Tomcat shuts down as it should. But I'm wondering if this is the way to go.. Can a RabbitMQ cluster deal with thousands (or even millions) of short living queues/consumers? I can imagine queues aren't that big, but still.. constantly broadcasting to all cluster nodes.. the total memory footprint..

Question

So in short, is it wise do create a queue for each incoming web request or how should I setup RabbitMQ with one queue and consumer so Tomcat can shutdown gracefully?

Upvotes: 1

Views: 1667

Answers (1)

willemsst
willemsst

Reputation: 51

I found a solution for my problem:

The Java client is creating his own threads. There is the possibility to add your own ExecutorService when creating a new connection. Doing so in the ServletContextListener.initialized() method, one can keep track of the ExecutorService and shut it down manually in the ServletContextListener.destroyed() method.

executorService.shutdown();
executorService.awaitTermination(20, TimeUnit.SECONDS);

I used Executors.newCachedThreadPool(); as the threads have many short executions, and they get cleaned up when being idle for more then 60s.

This is the link to the RabbitMQ Google group thread (thx to Michael Klishin for showing me the right direction)

Upvotes: 4

Related Questions