Task triggered service

You can use Cloud Tasks for async task execution with useful features such as task de-duplication, rate and retry controls, future scheduling and more. You can read more in Cloud Tasks docs. The following blog posts are also useful in understanding use cases for Cloud Tasks:

• Asynchronous Code Execution with Google Cloud Tasks by Grant Timmerman.
• Cloud Tasks is a little stateful by Adam Ross.

You can use Cloud Run as an HTTP target handler for Cloud Tasks:

Enable Cloud Tasks

First, make sure the Cloud Tasks API is enabled in your project:

gcloud services enable cloudtasks.googleapis.com

Create a 'Event Display' service

Take a look at the service we already created in event-display folder. It simply logs out the HTTP request body. We'll use it to display the received messages.

Build the container

In folder where Dockerfile resides, build the container using Cloud Build and push it to Container Registry:

gcloud builds submit \
  --project ${PROJECT_ID} \
  --tag gcr.io/${PROJECT_ID}/event-display

Deploy to Cloud Run

Note that we're deploying with no-allow-unauthenticated flag. We only want Cloud Tasks to trigger the service:

export SERVICE_NAME=event-display-tasks

gcloud run deploy ${SERVICE_NAME} \
  --image gcr.io/${PROJECT_ID}/event-display \
  --platform managed \
  --no-allow-unauthenticated

Setup Cloud Tasks to trigger Cloud Run

Create a service account:

export SERVICE_ACCOUNT=cloudrun-tasks-sa

gcloud iam service-accounts create ${SERVICE_ACCOUNT} \
   --display-name "Cloud Run Tasks Service Account"

Give service account permission to invoke the Cloud Run service:

gcloud run services add-iam-policy-binding event-display-tasks \
   --member=serviceAccount:${SERVICE_ACCOUNT}@${PROJECT_ID}.iam.gserviceaccount.com \
   --role=roles/run.invoker

Create a task queue

Create a Cloud Tasks queue:

export QUEUE_NAME=cloudrun-queue

gcloud tasks queues create ${QUEUE_NAME}

Create a task

You can create tasks programmatically or using gcloud. Here, we'll use gcloud for simplicity. Make sure you replace the url with your own Cloud Run service url you deployed earlier:

export SERVICE_URL="$(gcloud run services list --platform managed --filter=${SERVICE_NAME} --format='value(URL)')"

gcloud tasks create-http-task --queue ${QUEUE_NAME} \
  --url ${SERVICE_URL} \
  --body-content "Hello World from Cloud Tasks" \
  --oidc-service-account-email=${SERVICE_ACCOUNT}@${PROJECT_ID}.iam.gserviceaccount.com \
  --oidc-token-audience=${SERVICE_URL}

Test the service

You can check the logs of the service to see that it's been triggered by the Cloud Tasks:

2019-11-28 09:55:09.946 GMT Event Display received event: Hello World from Cloud Tasks