Cloud Functions + Pub/Sub Message Ordering + Terraform

This sample demonstrates deploying a Python Google Cloud Function that is triggered by a manually configured Pub/Sub topic. The sample can be deployed using terraform:

NOTE: You should replace the PROJECT_ID in ./terraform/main.tf with your own GCP project ID

cd ./terraform/
terraform init
terraform plan
terraform apply

Then send a message to the Pub/Sub topic to trigger the function:

gcloud pubsub topics publish projects/PROJECT_ID/topics/message-ordering-topic \
  --message=hello \
  --attribute=foo="bar" \
  --ordering-key=5

View the function logs to observe the invocation:

gcloud functions logs read pubsub-message-ordering-cloud-function --region="us-central1" --project=PROJECT_ID

Explanation

This sample uses the new declarative functions signatures API to configure the signature type of the cloud function using a Python decorator:

@functions_framework.cloud_event
def on_message(cloud_event):

This enables automatic request marshaling to convert the incoming HTTP request into a CloudEvent.

The function is then deployed using an HTTP trigger and its trigger_url is used to manually configure the Pub/Sub subscription:

push_config {
    push_endpoint = google_cloudfunctions_function.function.https_trigger_url
}

HEADS UP

There is a bug in the Python functions frameworks that breaks automatic cloudevent marshaling of Pub/Sub payloads that do not include any attributes.

matthewrobertson/gcf-pubsub-message-ordering

Cloud Functions + Pub/Sub Message Ordering + Terraform

Explanation

HEADS UP