Jira is an event-driven system. This means that, when an action occurs (for example, when an issue is created), Jira usually fires off a corresponding event. This event is then picked up by components that are designed to listen to the event. Not surprisingly, these are called listeners. When a listener picks up an event, it will perform its duty, such as keeping issues up to date with changes or sending an email to users who are watching the issue.

This mechanism allows Jira to process operations asynchronously. The advantage of this model is operations, such as sending emails, and it's separated from Jira's core functions such as issue creation. If there is a problem with the mail server, for example, you will not want this problem to prevent your users from creating issues.

There are two types of event in Jira:

• System events: These are internal events that...