Eventarc: ACE Exam Study Guide (2026)

Image source: Google Cloud Documentation

1. Eventarc Overview

Eventarc is a fully managed eventing service that routes events from various sources to specific destinations using the CloudEvents specification.

• Fully Managed: No infrastructure to manage; scales automatically.
• Decoupling: Enables asynchronous communication between producers and consumers.
• Standardization: Uses CloudEvents 1.0 for consistent event format.
• Regional: Triggers must be in the same region as the destination service.

2. Core Components

• Event: A record of something that happened (e.g., a file uploaded to Cloud Storage).
• Trigger: A filter that defines which events to route to which destination.
• Destination: The service that receives and processes the event (Cloud Run, Cloud Functions, GKE, Workflows).
• Event Channel: A pathway to receive events from non-Google sources (SaaS, custom apps).

3. Event Sources

• Direct Sources: Cloud Storage, Pub/Sub, Firestore, BigQuery (have built-in event types).
• Cloud Audit Logs: Any GCP service that writes to Audit Logs can trigger events. Use when a service lacks direct Eventarc support.
• Pub/Sub: Route existing Pub/Sub messages through Eventarc.
• Third-party (SaaS): Datadog, PagerDuty, etc. via Event Channels.
• Custom Applications: Your own apps can publish events via Event Channels.
• Discovery: gcloud eventarc events list --location=[REGION] shows available event types.

4. Event Destinations

• Cloud Run (Services)
• Cloud Functions (2nd Gen - Eventarc is the underlying engine)
• GKE (via k8s triggers)
• Workflows (orchestrate multi-step processes)
• Internal Load Balancers

5. Event Filters

Triggers use AND logic - all specified filters must match:

• Single: --event-filters="type=google.cloud.storage.object.v1.finalized"
• Multiple: --event-filters="type=google.cloud.storage.object.v1.finalized" --event-filters="bucket=my-bucket"
• Common filters: type, bucket, serviceName, methodName

6. CloudEvents Format

{
  "id": "test-event-id",
  "source": "//storage.googleapis.com/buckets/my-bucket",
  "type": "google.cloud.storage.object.v1.finalized",
  "datacontenttype": "application/json",
  "data": { "bucket": "my-bucket", "name": "my-file.txt" }
}

7. Security and IAM

• Service Account: Needs roles/eventarc.eventReceiver to receive events and roles/run.invoker to invoke destinations.
• Roles:
  • roles/eventarc.admin: Full control
  • roles/eventarc.viewer: Read-only

8. Essential gcloud Commands

• Create Trigger: gcloud eventarc triggers create [NAME] --destination-run-service=[SVC] --destination-run-region=[REGION] --event-filters="type=google.cloud.storage.object.v1.finalized" --event-filters="bucket=[BUCKET]" --service-account=[SA_EMAIL]
• List Triggers: gcloud eventarc triggers list --location=[REGION]
• Create Channel: gcloud eventarc channels create [NAME] --location=[REGION]

9. Failure Handling

• At-least-once delivery: Retries with exponential backoff on failure.
• No dead letter queue: Handle failures in the destination service.
• Idempotency required: Destinations must handle duplicate deliveries.

10. Eventarc vs Pub/Sub

Use Pub/Sub: High-throughput, complex filtering, any message format. Use Eventarc: GCP-managed routing, CloudEvents format, serverless triggers.

11. Exam Tips

• 2nd Gen Cloud Functions use Eventarc internally.
• Cloud Audit Logs enables triggering on ANY GCP operation.
• Triggers are regional; match destination region.
• Event Channels bridge non-Google sources into Eventarc.