Trigger Specification

This specification describes the gcp-pubsub trigger for Google Cloud Platform Pub/Sub.

triggers:
- type: gcp-pubsub
  authenticationRef: gcp-pubsub-credentials # Required
  metadata:
    subscriptionSize: "5" # Deprecated, use mode and value fields instead
    mode: "SubscriptionSize" # Optional - Default is SubscriptionSize - SubscriptionSize or OldestUnackedMessageAge
    value: "5" # Optional - Default is 5 for SubscriptionSize | Default is 10 for OldestUnackedMessageAge
    subscriptionName: "mysubscription" # Required

The Google Cloud Platform (GCP) Pub/Sub trigger allows you to scale based on the number of messages or oldest unacked message age in your Pub/Sub subscription.

authenticationRef defines how KEDA connect to Google Cloud Platform, to collect the required stack driver metrics in order to read the number of messages in the Pub/Sub subscription.

subscriptionName defines the subscription that should be monitored. You can use different formulas:

• Just the subscription name, in which case you will reference a subscription from the current project or the one specified in the credentials file used.
• Use the full link provided by Google, so that you can reference a subscription that is hosted in another project Eg: projects/myproject/subscriptions/mysubscription.

You can use either subscriptionSize to define the target average which the deployment will be scaled on or mode and value fields. subscriptionSize field is deprecated, it is recommended to use mode and value fields instead. Scaler will not work if you define both subscriptionSize and at least one of mode or value. The mode chooses whether to scale using number of messages SubscriptionSize or using oldest unacked message age OldestUnackedMessageAge. The value determines the target average which the deployment will be scaled on. The default value is 5 for SubscriptionSize and 10 for OldestUnackedMessageAge.

Here’s an example.

Authentication Parameters

You can configure authorization for a ScaledObject either directly using credentials in credentialsFromEnv or using an authenticationRef referencing a TriggerAuthentication CRD which configures authorization.

Pod identity based authentication:

• podIdentity.provider - Needs to be set to gcp on the TriggerAuthentication and the pod’s Workload Identity or node’s (default) service account must be configured correctly.

Credential based authentication via TriggerAuthentication:

• secretTargetRef - Needs to be set on the TriggerAuthentication, with parameter=GoogleApplicationCredentials and name must reference a Secret in which key is the key containing the JSON ServiceAccount value.

Credential based authentication via ScaledObject:

• credentialsFromEnv - Needs to be set on the ScaledObject.

Examples

To use the GCP default authentication, you need to create a TriggerAuthentication as this example, and reference it in the ScaledObject.

apiVersion: keda.sh/v1alpha1
kind: TriggerAuthentication
metadata:
  name: gcp-pubsub-credentials
spec:
  podIdentity:
    provider: gcp # Required
---
apiVersion: keda.sh/v1alpha1
kind: ScaledObject
metadata:
  name: pubsub-scaledobject
spec:
  scaleTargetRef:
    name: keda-pubsub-go
  triggers:
  - type: gcp-pubsub
    metadata:
      subscriptionName: "input" # Required
    authenticationRef:
      name: gcp-pubsub-credentials

Alternatively, you can configure the credentials in a secret, via the TriggerAuthentication:

apiVersion: v1
kind: Secret
metadata:
  name: pubsub-secret
data:
  GOOGLE_APPLICATION_CREDENTIALS_JSON: <json-credential-value>
---
apiVersion: keda.sh/v1alpha1
kind: TriggerAuthentication
metadata:
  name: gcp-pubsub-credentials
spec:
  secretTargetRef:
  - parameter: GoogleApplicationCredentials
    name: pubsub-secret  # Required. Refers to the name of the secret
    key: GOOGLE_APPLICATION_CREDENTIALS_JSON # Required
---
apiVersion: keda.sh/v1alpha1
kind: ScaledObject
metadata:
  name: pubsub-scaledobject
spec:
  scaleTargetRef:
    name: keda-pubsub-go
  triggers:
  - type: gcp-pubsub
    metadata:
      subscriptionName: "input" # Required
    authenticationRef:
      name: gcp-pubsub-credentials # Required

The credentialsFromEnv property maps to the name of an environment variable in the scale target (scaleTargetRef) that contains the service account credentials (JSON).

apiVersion: keda.sh/v1alpha1
kind: ScaledObject
metadata:
  name: pubsub-scaledobject
  namespace: keda-pubsub-test
spec:
  scaleTargetRef:
    name: keda-pubsub-go
  triggers:
  - type: gcp-pubsub
    metadata:
      subscriptionSize: "5"
      subscriptionName: "mysubscription" # Required
      credentialsFromEnv: GOOGLE_APPLICATION_CREDENTIALS_JSON # Required

Example using ClusterTriggerAuthentication with GCP Identity

apiVersion: keda.sh/v1alpha1
kind: ClusterTriggerAuthentication
metadata:
  name: keda-clustertrigger-auth-gcp-credentials
spec:
  podIdentity:
    provider: gcp
---
apiVersion: keda.sh/v1alpha1
kind: ScaledObject
metadata:
  name: pubsub-scaledobject
spec:
  scaleTargetRef:
    name: keda-pubsub-go
  triggers:
  - type: gcp-pubsub
    authenticationRef:
      name: keda-clustertrigger-auth-gcp-credentials
      kind: ClusterTriggerAuthentication
    metadata:
      subscriptionName: "input" # Required