Terminology

Before you read more about Catalyst Event Listeners, ensure that you understand the following terms in the context of Catalyst:

• Event Listener: An event listener, whether component event listener, custom, or a Zoho event listener can trigger the execution ofevent functions, or a circuits. It cannot trigger the execution of any other type of function, and an event function cannot be invoked in any other way. You can associate multiple rules with an event listener, and each rule can trigger multiple event functions or any target circuits.

  When an event listener is created in Catalyst, a unique Event Listener ID is created for it automatically. This ID and the name of the event listener are passed as part of the event bus details to the target function or circuit. Each project can contain a maximum of five event listeners: four custom and one component event listeners.

• Rules: A rule defines the specific action that will trigger the component or custom event listener.

  • Component event listener: A rule is associated with the instances of a particular component, and a set of actions occurring in them.
  • Custom event listener: Each rule acts as an individual instance of the event listener and is identified by a unique rule identifier.
  • Zoho event listener: A rule is associated with a specific event occurring in an associated Zoho service.
    
    You will learn about this in detail in the next section.
    
    A rule matches the incoming event with the execution of the associated event function or target circuit and routes the data for processing. A unique Rule ID is automatically created when you create a rule for an event listener.

• Events:

  • Component event listener: A specific action occurring in a component is considered to be an event. For example, a table in the Data Store being updated or a user signing up for your application. The complete list of component events is given in the next section.
  • Custom event listener: An event is said to have occurred when the event listener’s URL is invoked by the end-user of your application.
  • Zoho event listener: A specific action occurring in an external Zoho service, such as Zoho CRM. For example, Leads Created, Sales Order Updated, Campaigns Approved, or Email Sent in the CRM account associated with the particular rule.

• Queued Events: When an event for which an event listener rule has been configured has occurred, the associated rule will be triggered. The event will then be queued for processing. Each event listener that you create will have its individual queue. Catalyst will invoke the associated target functions or circuits for execution during the processing, and pass the event data to them. After the function or circuit completes its execution, or if it fails to execute, the event will be removed from the queue.
  
  

  For example, if you had configured a rule with a table insert event in the Data Store, the component event listener will be listening for an insert action in that table. When that action occurs, the associated rule will be triggered, and the event will be queued for processing. In the case of a custom event listener, when the URL of the event listener is invoked, the event will be queued until the rule has triggered the associated functions and they complete their execution. You can view detailed information of events when they enter a queue and are being processed from the Queued Events section in the console.

• Processed Events: After the associated target function or a circuit of a component or a custom event listener rule executes successfully, it will be considered as a processed event. The Processed Events section in the console will contain detailed information about the event traffic and execution history of each rule that was executed.

• Failed Events: If the execution of the associated target functions or circuits of a component or a custom event listener rule is a failure, or if the rule fails to invoke the target functions or circuits for any reason, it will be considered as a failed event.