Complex event processing engines are a natural fit for event driven platforms like Mule. Native CEP support has been available in Mule since version 3.2 by way of the Drools Module. The Esper Module now offers an alternate way to leverage CEP in your integration applications. Esper is a robust, performant, open source, complex event processing engine. Let’s take a look at how to use Esper with Mule and then see how it compares to Drools’ CEP support.
When you send a request to an API and it gets processed the API might want to notify you app about the status of the request. In order for your application to handle this callback you would have to set up an endpoint to listen for the notification and then send the url of that endpoint to the API. For example Twilio, one of the most popular public APIs, uses callbacks to tell you whether a SMS message has been successfully delivered or not in addition to a SMS id that you can use later for tracking purposes. Since the goal of the new Mule DevKit is to make things simpler it provides an easy way to handle HTTP callbacks.