Trigger

Triggers Nodes in Cortex are designed to periodically generate empty events with only a timestamp attribute based on a specified time interval or cron expression. They function similarly to Stream Nodes and can be utilized as Stream Nodes.

Trigger Node produces empty events; i.e. events without any data but only with a timestamp.

Trigger Nodes enable users to periodically execute Application flows for automated event generation.

Their main purpose is to enable the periodic execution of queries and can also be activated at SiddhiApp startup for initialization tasks, offering a versatile tool for automated event generation and system preparation.

Step 1 - General

Name and Description

When configuring a Trigger Node in Cortex, Step 1 involves several key actions.

• Assign a unique name to the Node, distinct from other Nodes in your Application.

• Optionally, add a Description for detail and clarity.

• The Node Name and Description will help distinguish it in the Canvas via Node Preview.

Attributes

Different from any other Node in Cortex, Trigger Node do not allow the user to interact with its attributes at all. This is beacuse of nature of the Trigger Node.

As Trigger Node produces empty events with only a timestamp; the sole Attribute's Attribute Type can only be timestamp -so it's set as such for convenience.

Step 2 - Trigger Criterion

In the Trigger Node, 3 different types of triggers are designed to automate event production through various mechanisms.

Trigger Type
Start	Produces a single empty event with only a timestamp when the Application is run on a Runner.
Period	Repeatedly produces empty events with only a timestamp in a given period
Cron Expression	Repeatedly produces empty events with only a timestamp according to a cron expression.

Step 3 - Preview

In Preview Step, you're provided with a concise summary of all the changes you've made to the Trigger Node. This step is pivotal for reviewing and ensuring that your configurations are as intended before completing node setup.

• Viewing Configurations: Preview Step presents a consolidated view of your node setup.

• Saving and Exiting: Use the Complete button to save your changes and exit the node and return back to Canvas.

• Revisions: Use the Back button to return to any Step of modify node setup.

The Preview Step offers a user-friendly summary to manage and finalize node settings in Cortex.