12. Understanding messaging and scheduling

In this chapter What messaging is and how it works How messaging aids scalable architectures Points in your Grails application that benefit from messaging How to implement queues and topics with a popular JMS server How scheduling is implemented in Grails Scheduling jobs with cron-style expressions Programmatically creating and managing scheduled jobs Advanced scheduling use cases for persistent and clustered jobs

In the last chapter, we spent some time investigating remoting options for Grails applications and looked at generating and consuming interapplication messages. In this chapter, we’ll keep you in that enterprise headspace, but we’ll look at sending intra-application messages. In particular, we’ll examine how different components in an application can communicate internally while different events in the application’s lifecycle unfold. One of the most popular ways of doing that is via messaging queues, an architecture sometimes referred to as message-oriented middleware (MOM).