Twitter ephemerality for Cloud Run

What does this do?

The guts are in app.rb

This repo demonstrates how you can create an inexpesive scheduled task to remove tweets from your timeline that are a certain age. This is accomplished via a ruby script that is packaged for Google Cloud Platform's new service Google Cloud Run.

To accomplish this we make use of the following services:

• Google Cloud Scheduler - to send a message to a topic periodically
• Google Cloud Pub/Sub - to create a topic and and subscription. The subscription calls our Cloud Run service.
• Google Cloud Run - to define our task, and make it available as a service.

We'll use the gcloud command line tool as much as possible to get this all running.

Big picture

We are going to:

1. Create a Cloud Run service that is invokable. This service will NOT be publicly accessible.
2. Create a job in Cloud Scheduler to periodically ( once a week ) push a message to a Pub/Sub topic.
3. Create a Cloud Pub/Sub topic for Cloud Scheduler to publish to.
4. Create a Cloud Pub/Sub subscription that will subscribe to the topic we created, and invoke our Cloud Run service using a service account with the Google Run Invoker privilage.

Why Ruby?

TL;DR I work at Shopify now.

You can use pretty much any language you want. See the Cloud Run docs.

Steps to make this work

Keep in mind you can go into the console to setup most of this, but where possible we'll use the gcloud command line tool.

1. Install the gcloud command line tool. Then run:

  gcloud components install
  gcloud components update

2. Setup a new project in the Google Cloud Console.

gcloud projects create my-example-project-id --name="my test project" --set-as-default

3. Enable billing for your project by following these instructions.

4. Enable the services we need for this project.

 gcloud services enable pubsub
 gcloud services enable cloudscheduler.googleapis.com
 gcloud services enable run.googleapis.com

4. Create the pubsub topic

  gcloud pubsub topics create run-trigger

5. Go to developers.twitter.com and create an application, and get your authentication credentials. You'll need these in Step 7.

6. Build this project and ship it to Google Container Registry. You must provide Environment Variables for the following keys:

  gcloud builds submit --tag gcr.io/[PROJECT-ID]/[IMAGE]

7. Now you'll actually setup the Cloud Rub service. You'll need to set the following ENV variables.

• TWITTER_CONSUMER_KEY
• TWITTER_CONSUMER_SECRET
• TWITTER_ACCESS_TOKEN
• TWITTER_ACCESS_TOKEN_SECRET
• RUN_PROJECT_ID - use the friendly name you gave your project in step 2 (--name=)

[IMAGE] - arbitrary name - you'll need this later though. [PROJECT-ID] - the google project id. [YOUR_SERVICE_NAME] - whatever you want to call the Cloud Run Service

  gcloud config set run/region us-central1
  
  gcloud beta run deploy [YOUR_SERVICE_NAME] --image gcr.io/tn-test-project-99/runservice --update-env-vars RUN_PROJECT_ID=YOUR_PROJECT_ID,TWITTER_CONSUMER_KEY=VALUE1,TWITTER_CONSUMER_SECRET=VALUE2,TWITTER_ACCESS_TOKEN=VALUE3,TWITTER_ACCESS_TOKEN_SECRET=VALUE4 --quiet

When this has finished you'll see output from the gcloud tool that looks like:

Deploying container to Cloud Run service [runservice] in project [tn-test-project-99] region [us-central1]
✓ Deploying new service... Done.                                                                                                                                                                                            
  ✓ Creating Revision...                                                                                                                                                                                                    
  ✓ Routing traffic...                                                                                                                                                                                                      
Done.                                                                                                                                                                                                                       
Service [runservice] revision [runservice-00001] has been deployed and is serving traffic at https://runservice-xtu6b5owbq-uc.a.run.app

You'll need the url that resembles https://runservice-xtu6b5owbq-uc.a.run.app at the end for step 9.

8. Go here and create a new service account. Call it cloud-run-invoker, click create, then give it the role of Cloud Run Invoker in the drop down list. You don't need to create any keys for this account. Now copy the email address associated with the new service account which should look something like: cloud-run-invoker@[project-id].iam.gserviceaccount.com

9. We now have to create the PubSub subscription, that will call our Cloud Run service. Remember we named our PubSub topic run-trigger we'll use that now and tell our subscription to impersonate the service account when calling our push endpoint ( our Cloud Run service ).

gcloud pubsub subscriptions create [SUBSCRIPTION_NAME] --topic run-trigger --topic-project=[PROJECT-ID] --ack-deadline=20 --push-endpoint=[URL_FROM_LAST_STEP] --impersonate-service-account=[SERVICE-ACCOUNT-EMAIL]

10. Go here and create a new job. Give it a name, and choose pubsub as the target, and enter in our pubsub topic name from step 4, which we called 'run-trigger'. Go ahead and setup a schedule, something like: '0 9 * * 1' should work - 9am every Monday morning.

11. You're done. You can manually trigger the Scheduler here. Use the log viewer here to see the log output.