Trigger Specification

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

triggers:
- type: gcp-pubsub
  metadata:
    subscriptionSize: "5" # Deprecated, use mode and value fields instead
    mode: "SubscriptionSize" # Optional - Default is SubscriptionSize - SubscriptionSize or OldestUnackedMessageAge
    aggregation: "sum" # Optional - Only meaningful for distribution-valued metrics
    value: "5.5" # Optional - Default is 10
    activationValue: "10.5" # Optional - Default is 0
    # Exactly one of the subscription or topic name options is required
    subscriptionName: "mysubscription"
    subscriptionNameFromEnv: "MY_SUBSCRIPTION_FROM_ENV"
    topicName: "mytopic"
    topicNameFromEnv: "MY_TOPIC_FROM_ENV"
    credentialsFromEnv: GOOGLE_APPLICATION_CREDENTIALS_JSON # Required

The Google Cloud Platform (GCP) Pub/Sub trigger allows you to scale based on any metrics from your Pub/Sub subscription or topic, such as number of messages or oldest unacked message age, etc.

• credentialsFromEnv - This property maps to the name of an environment variable in the scale target (scaleTargetRef) that contains the service account credentials (JSON). KEDA will use those to connect to Google Cloud Platform and collect the required stack driver metrics in order to read the number of messages in the Pub/Sub subscription.

• mode - The metric used to scale your workload. It’s the PascalCase of the official metric name. For example, if you are going to leverage the metric subscription/pull_request_count, you will fill the value as PullRequestCount. Please refer to https://cloud.google.com/monitoring/api/metrics_gcp#gcp-pubsub. All metrics starting with subscription/ and topic/ are supported. (Default: SubscriptionSize, aka NumUndeliveredMessages)

• aggregation - The aggregation function used to aggregate the metric. (Values: mean, median, variance, stddev, sum, count, percentileX (X: an integer in the range 0 to 100), Required for metrics with value type DISTRIBUTION)

• activationValue - Target value for activating the scaler. Learn more about activation here.(Default: 0, Optional, This value can be a float)

• 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.

• subscriptionNameFromEnv - The name of an environment variable on the scale target that holds the subscription name. The resolved name is processed the same as subscriptionName.

• topicName defines the topic that should be monitored. Similar to susbcriptionName, you can use different formulas:

  • Just the topic name, in which case you will reference a topic 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 topic that is hosted in another project Eg: projects/myproject/topics/mytopic.

• topicNameFromEnv - The name of an environment variable on the scale target that holds the topic name. The resolved name is processed the same as topicName.

Here’s an example.

Authentication Parameters

You can use TriggerAuthentication CRD to configure the authenticate by providing the service account credentials in JSON.

Credential based authentication:

• GoogleApplicationCredentials - Service account credentials in JSON.

Example

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:
      mode: "SubscriptionSize"
      value: "5"
      subscriptionName: "mysubscription" # Required
      credentialsFromEnv: GOOGLE_APPLICATION_CREDENTIALS_JSON # Required

Example using distribution-valued metric and aggregation

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:
      # Example: https://cloud.google.com/pubsub/docs/monitoring#monitoring_message_throughput_2
      mode: "MessageSizes"
      aggregation: "count" # Calculate count of messages being published
      value: "50"
      topicName: "mytopic" # Required
      credentialsFromEnv: GOOGLE_APPLICATION_CREDENTIALS_JSON # Required

Example using TriggerAuthentication

apiVersion: keda.sh/v1alpha1
kind: TriggerAuthentication
metadata:
  name: keda-trigger-auth-gcp-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
    authenticationRef:
      name: keda-trigger-auth-gcp-credentials
    metadata:
      subscriptionName: "input" # Required

Identity based authentication:

You can also use TriggerAuthentication CRD to configure the authentication using the associated service account of the running machine in Google Cloud. You only need to create a TriggerAuthentication as this example, and reference it in the ScaledObject. ClusterTriggerAuthentication can also be used if you intend to use it globally in your cluster.

Example using TriggerAuthentication with GCP Identity

apiVersion: keda.sh/v1alpha1
kind: TriggerAuthentication
metadata:
  name: keda-trigger-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-trigger-auth-gcp-credentials
    metadata:
      subscriptionName: "input" # 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