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# Mule Events

> For the full documentation index, see: https://docs.mulesoft.com/llms.txt

A Mule event contains the core information processed by the runtime. It travels through components
inside your Mule app following the configured application logic.

Note that the Mule event is immutable, so every change to an instance of a Mule event results in the
creation of a new instance.

A Mule event is composed of these objects:

- A Mule Message contains a message payload and its associated attributes.

- Variables are Mule event metadata that you use in your flow.

![A Mule event including message, attributes, payload, and variables](/mulesoft/current/en-us/mule-runtime/4.9/_images/mule-concepts-d46f9.png)

A Mule event source (previously called a "message source") triggers the generation of a Mule event
and dispatches that event to the flow. Examples of event sources include triggers, such as the
Scheduler, and listeners, such as the HTTP Listener and On New or Updated File components.

![A Mule event source sequence](/mulesoft/current/en-us/mule-runtime/4.9/_images/about-mule-event-2724e.png)

1.  A trigger reaches the event source.

2.  The event source produces a Mule event.

3.  The Mule event travels sequentially through the components of a flow.

4.  Each component interacts in a pre-defined manner with the Mule event.

In some cases when an issue occurs in an event source, the component does not produce a Mule event.
For example, invalid or incorrect paths in an HTTP listener configuration prevents the creation of a
Mule event. Connectors log such issues in ERROR, WARN, or INFO messages.

## See Also

- [Mule Message Structure](https://docs.mulesoft.com/mule-runtime/4.9/about-mule-message)

- [Predefined Variables](https://docs.mulesoft.com/dataweave/latest/dataweave-variables-context)

- [Variables in Mule Events](https://docs.mulesoft.com/mule-runtime/4.9/about-mule-variables)

- [Logging and Debugging](https://docs.mulesoft.com/mule-runtime/4.9/logging-and-debugging)

- [Mule Errors](https://docs.mulesoft.com/mule-runtime/4.9/mule-error-concept)