Associating triggers and actions through rules

IBM Cloud® Functions is deprecated. Existing Functions entities such as actions, triggers, or sequences will continue to run, but as of 28 December 2023, you can’t create new Functions entities. Existing Functions entities are supported until October 2024. Any Functions entities that still exist on that date will be deleted. For more information, see Deprecation overview.

In IBM Cloud® Functions, every time the trigger fires, the rule uses the trigger event as input and invokes the associated action. With the appropriate set of rules, it's possible for a single trigger to invoke multiple actions, or for an action to be invoked as a response to events from multiple triggers.

Creating a rule from the console

From the console, the rule to associate an action and a trigger is created for you.

When you create or access the details for an action or trigger, you have the option of connecting an existing or a new action or trigger. When you make the connection, a rule is created for you and is named in the format ACTION_NAME-TRIGGER_NAME.

From the CLI, you can run ibmcloud fn rule list to verify that the rule was created for you.

Creating rules from the CLI

Rules are used to associate a trigger with an action. Each time a trigger event is fired, the action is invoked with the parameters from the trigger event.

Before you begin, create an action and a trigger.

Create a rule to associate a trigger with an action. Rules must be created directly within a namespace and can't be created inside packages.

ibmcloud fn rule create RULE_NAME TRIGGER_NAME ACTION_NAME

To disable the rule, you can run the following command.

ibmcloud fn rule disable RULE_NAME

Creating rules for action sequences

You can use rules to associate triggers with action sequences.

Before you begin, create an action sequence and a trigger.

ibmcloud fn rule create RULE_NAME TRIGGER_NAME ACTION_SEQUENCE_NAME

Associating multiple triggers and actions

You can use different combinations of triggers and actions by creating a rule for each combination. You are not required to have a one to one ratio for actions and triggers.

For example, consider the following actions.

Table 1. Actions and descriptions
Action	Description
`classifyImage`	An action that detects the objects in an image and classifies them.
`thumbnailImage`	An action that creates a thumbnail version of an image.

Also, suppose that two event sources are firing the following triggers.

Table 2. Event triggers and descriptions
Trigger	Description
`newTweet`	A trigger that is fired when a new tweet is posted.
`imageUpload`	A trigger that is fired when an image is uploaded to a website.

You can set up rules so that a single trigger event invokes multiple actions, and have multiple triggers invoke the same action.

newTweet -> classifyImage rule
imageUpload -> classifyImage rule
imageUpload -> thumbnailImage rule

The three rules establish the following behavior.

Images in both tweets are classified.
Uploaded images are classified
A thumbnail version is generated.