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¶

Fetch the project credentials JSON file from GCP console.

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

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

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

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

Publish a message from GCP Pub/Sub console.
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:

Access control | Cloud Pub/Sub Documentation | Google Cloud ⧉

Troubleshoot¶

Please read the FAQ.