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GCP Pub/Sub

GCP Pub/Sub event-source subscribes to messages published by GCP publisher and helps sensor trigger workloads.

Event Structure

The structure of an event dispatched by the event-source over the eventbus looks like following,

{
    "context": {
      "type": "type_of_event_source",
      "specversion": "cloud_events_version",
      "source": "name_of_the_event_source",
      "id": "unique_event_id",
      "time": "event_time",
      "datacontenttype": "type_of_data",
      "subject": "name_of_the_configuration_within_event_source"
    },
    "data": {
        "id": "message id",
        // Attributes represents the key-value pairs the current message
        // is labelled with.
        "attributes": "key-values",
        "publishTime": "// The time at which the message was published",
        "body": "body refers to the message data",
    }
}

Specification

GCP Pub/Sub event-source specification is available here.

Setup

  1. Fetch the project credentials JSON file from GCP console.

    If you use Workload Identity, you can skip this and next steps.

  2. Create a K8s secret called gcp-credentials to store the credentials file.

    apiVersion: v1
data:
  key.json: <YOUR_CREDENTIALS_STRING_FROM_JSON_FILE>
kind: Secret
metadata:
  name: gcp-credentials
  namespace: argo-events
type: Opaque

  3. Create the event source by running the following command.

    kubectl apply -n argo-events -f https://raw.githubusercontent.com/argoproj/argo-events/stable/examples/event-sources/gcp-pubsub.yaml

    If you use Workload Identity, omit credentialSecret field. Instead don't forget to configure appropriate service account (see example).

  4. Inspect the event-source pod logs to make sure it was able to subscribe to the topic.

  5. Create the sensor by running the following command.

    kubectl apply -n argo-events -f https://raw.githubusercontent.com/argoproj/argo-events/stable/examples/sensors/gcp-pubsub.yaml

  6. Publish a message from GCP Pub/Sub console.

  7. Once a message is published, an argo workflow will be triggered. Run argo list to find the workflow.

Subscription, topic and service account preparation

You can use existing subscriptions/topics, or let Argo Events create them.

Here's the table of which fields are required in the configuration file and what permissions are needed for service account.

Actions Required configuration fields Necessary permissions for service account Example role
Use existing subscription Existing SubscriptionID pubsub.subscriptions.consume for the subscription roles/pubsub.subscriber
Use existing subscription and verify topic Existing SubscriptionID and its Topic Above +
pubsub.subscriptions.get for the subscription		 roles/pubsub.subscriber
+ roles/pubsub.viewer
Create subscription for existing topic Existing Topic
(SubscriptionID is optional†)		 Above +
pubsub.subscriptions.create for the project
pubsub.topics.attachSubscription for the topic		 roles/pubsub.subscriber
+ roles/pubsub.editor
Create topic and subscription Non-existing Topic
(SubscriptionID is optional†)		 Above +
pubsub.topic.create for the project		 roles/pubsub.subscriber
+ roles/pubsub.editor

† If you omit SubscriptionID, a generated hash value is used.

For more details about access control, refer to GCP documents:

Troubleshoot

Please read the FAQ.

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