Creating triggers - Triggers | Eventing | Red Hat OpenShift Serverless 1.35

Creating a trigger by using the Administrator perspective
Creating a trigger by using the Developer perspective
Creating a trigger by using the Knative CLI

Triggers in Knative Eventing allow you to route events from a broker to a specific subscriber based on your requirements. By defining a Trigger, you can connect event producers to consumers dynamically, ensuring events are delivered to the correct destination. This section describes the steps to create a Trigger, configure its filters, and verify its functionality. Whether you’re working with simple routing needs or complex event-driven workflows.

The following examples displays common configurations for Triggers, demonstrating how to route events to Knative services or custom endpoints.

Example of routing events to a Knative Serving service

The following Trigger routes all events from the default broker to the Knative Serving service named my-service:

apiVersion: eventing.knative.dev/v1
kind: Trigger
metadata:
  name: my-service-trigger
spec:
  broker: default
  filter:
    attributes:
      type: dev.knative.foo.bar
  subscriber:
    ref:
      apiVersion: serving.knative.dev/v1
      kind: Service
      name: my-service

Routing all events without a filter attribute is recommended for debugging purposes. It allows you to observe and analyze all incoming events, helping identify issues or validate the flow of events through the broker before applying specific filters. To know more about filtering, see Advanced trigger filters.

To apply this trigger, you can save the configuration to a file, for example, trigger.yaml and run the following command:

$ oc apply -f trigger.yaml

Example of routing events to a custom path

This Trigger routes all events from the default broker to a custom path /my-custom-path on the service named my-service:

apiVersion: eventing.knative.dev/v1
kind: Trigger
metadata:
  name: my-service-trigger
spec:
  broker: default
  subscriber:
    ref:
      apiVersion: v1
      kind: Service
      name: my-service
    uri: /my-custom-path

You can save the configuration to a file, for example, custom-path-trigger.yaml and run the following command:

$ oc apply -f custom-path-trigger.yaml

Creating a trigger by using the Administrator perspective

Using the OpenShift Container Platform web console provides a streamlined and intuitive user interface to create a trigger. After Knative Eventing is installed on your cluster and you have created a broker, you can create a trigger by using the web console.

Prerequisites

The OpenShift Serverless Operator and Knative Eventing are installed on your OpenShift Container Platform cluster.
You have logged in to the web console and are in the Administrator perspective.
You have cluster administrator permissions on OpenShift Container Platform, or you have cluster or dedicated administrator permissions on Red Hat OpenShift Service on AWS or OpenShift Dedicated.
You have created a Knative broker.
You have created a Knative service to use as a subscriber.

Procedure

In the Administrator perspective of the OpenShift Container Platform web console, navigate to Serverless → Eventing.
In the Broker tab, select the Options menu for the broker that you want to add a trigger to.
Click Add Trigger in the list.
In the Add Trigger dialogue box, select a Subscriber for the trigger. The subscriber is the Knative service that will receive events from the broker.
Click Add.

Creating a trigger by using the Developer perspective

Prerequisites

The OpenShift Serverless Operator, Knative Serving, and Knative Eventing are installed on your OpenShift Container Platform cluster.
You have logged in to the web console.
You have created a project or have access to a project with the appropriate roles and permissions to create applications and other workloads in OpenShift Container Platform.
You have created a broker and a Knative service or other event sink to connect to the trigger.

Procedure

In the Developer perspective, navigate to the Topology page.
Hover over the broker that you want to create a trigger for, and drag the arrow. The Add Trigger option is displayed.
Click Add Trigger.
Select your sink in the Subscriber list.
Click Add.

Verification

After the subscription has been created, you can view it in the Topology page, where it is represented as a line that connects the broker to the event sink.

Deleting a trigger

In the Developer perspective, navigate to the Topology page.
Click on the trigger that you want to delete.
In the Actions context menu, select Delete Trigger.

Creating a trigger by using the Knative CLI

You can use the kn trigger create command to create a trigger.

Prerequisites

The OpenShift Serverless Operator and Knative Eventing are installed on your OpenShift Container Platform cluster.
You have installed the Knative (kn) CLI.
You have created a project or have access to a project with the appropriate roles and permissions to create applications and other workloads in OpenShift Container Platform.

Procedure

Create a trigger:
```
$ kn trigger create <trigger_name> --broker <broker_name> --filter <key=value> --sink <sink_name>
```
Alternatively, you can create a trigger and simultaneously create the default broker using broker injection:
```
$ kn trigger create <trigger_name> --inject-broker --filter <key=value> --sink <sink_name>
```
By default, triggers forward all events sent to a broker to sinks that are subscribed to that broker. Using the --filter attribute for triggers allows you to filter events from a broker, so that subscribers will only receive a subset of events based on your defined criteria.