Event Functions

Introduction

An Event function is an asynchronous task function that is associated with an Event Listener. An Event function is created to execute a task or a set of tasks on the occurrence of a specified event.

The default Event Listener listens for an event occurring in one of the Catalyst components and the custom Event Listener listens for the invocation of a particular URL. When these events occur, the event function associated with that event listener instance is automatically invoked and executed.

You will not be able to invoke an Event function manually, or test it in the console or the CLI. The endpoint of an Event function is not accessible through a Function URL like Basic I/O or Advanced I/O functions are. An Event function does not return any response other than determining if the function execution was a success or failure.

You can create an Event function from the Catalyst console, and code it there, or use the CLI to initialize the function and deploy it to the console.

You can use various tools to manage your Advanced I/O functions and view their performance statistics such as Logs or Application Performance Monitoring, as mentioned in the Functions Introduction page.

You can practice working with Event functions with the Event Function tutorial or the WorkDrive Sync App tutorial.

Java, Node.js and Python Modules

A Catalyst Event function supports two modules in Node.js and Python: context and event.

The context module in Node.js and Python includes the following built-in methods:

1. context.closeWithSuccess():: To indicate that the function executed successfully. You must use this at the end of the function.
2. context.closeWithFailure():: To indicate that the function’s execution was a failure. You must use this at the end of the function.
3. context.get_remaining_execution_time_ms(): This can be used to fetch the remaining execution time of a function.
4. context.get_max_execution_time_ms():: This method can be used to get the maximum execution time of a function, which is a constant value of 15 minutes.

The event module in Node.js and Python includes the following built-in methods:

1. event.getProjectDetails():: To get the project details, such as the project ID and project name
2. event.getData():: To get the data about the event associated with the function
3. event.getTime():: To get the time of the event occurrence that invoked the function
4. event.getSource():: To get the ID of the source entity where the event occurred, such as the Table ID or a cache’s Segment ID
5. event.get_event_bus_details():: To get the details of the event bus such as the configured event actions and rules.

An Event function in Java supports the same modules and built-in methods as Node.js and Python. Some additional methods supported in Java are:

1. event.getAction():: To get the action executed in the Catalyst components that triggered the event in the default Event Listener, such as data insertion in a table or a user sign-up
2. event.getSourceEntityID():: To get the ID of the source entity where the event occurred, such as the Table ID or a cache’s Segment ID

You can check the default code structure created for an Event function, based on the stack, from the Catalyst console or your function directory in your local system.