Here is how to acknowledge a message in a Cloud Run endpoint triggered by a push-type Pub/Sub subscription and prevent retries:
Acknowledgment in Push Subscriptions:
For push subscriptions, where Pub/Sub sends messages to your Cloud Run service endpoint, acknowledgment occurs implicitly through an HTTP response. There's no need for the .ack() or .nack() methods used in pull subscriptions.
Acknowledgement with 200 OK:
To acknowledge a message successfully and prevent retries, your Cloud Run service needs to respond with an HTTP 200 OK status code. This tells Pub/Sub that the message was processed successfully and shouldn't be redelivered.
Example Code:
The following Python code demonstrates how to handle message processing and acknowledgment in a Cloud Run service:
from flask import Flask, request
app = Flask(__name__)
@app.route('/', methods=['POST'])
def index():
envelope = request.get_json()
message = envelope['message']
try:
return '', 200
except Exception as e:
return '', 500
if __name__ == '__main__':
app.run(port=8080, debug=True)
Additional Considerations:
- Error Handling: Implement robust error handling and logging to capture any issues during message processing.
- Idempotency: Ensure your message processing logic is idempotent, meaning it can be safely executed multiple times without unintended consequences. This is important as Pub/Sub might redeliver messages even after successful acknowledgment in certain scenarios.
- Response Time: Be mindful of your service's response time. If it takes too long to respond, exceeding the acknowledgment deadline configured in the subscription, Pub/Sub might consider the message unreceived and send it again.
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