Google App Engine provides a Cron service. Using this service for scheduling and Google Cloud Pub/Sub for distributed messaging, you can build an application to reliably schedule tasks which can trigger Google Cloud Functions.

This sample contains two components:

• An App Engine application, that uses App Engine Cron Service to relay cron messages to Cloud Pub/Sub topics.

• A sample Cloud Function which triggers hourly.

By default this sample triggers hourly, daily, and weekly. If you want to customize this schedule for your app then you can modify the cron.yaml.

For details on configuring this, please see the cron.yaml Reference in the App Engine documentation.

The overview for configuring and running this sample is as follows:

• If you don’t already have one, create a Google Account.

• Create a Developers Console project.

  1. Install (or check that you have previously installed)
     • git
     • Python 2.7
     • Python pip
     • Google Cloud SDK
  2. Enable the Pub/Sub API
  3. Enable Project Billing

To clone the GitHub repository to your computer, run the following command:

$ git clone https://github.com/firebase/functions-cron

Change directories to the functions-cron directory. The exact path depends on where you placed the directory when you cloned the sample files from GitHub.

$ cd functions-cron

Leave the default cron.yaml as is for now to run through the sample.

1. Configure the gcloud command-line tool to use the project your Firebase project.

$ gcloud config set project <your-project-id>

2. Change directory to appengine/

$ cd appengine/

3. Install the Python dependencies

$ pip install -t lib -r requirements.txt

4. Create an App Engine App

$ gcloud app create

5. Deploy the application to App Engine.

$ gcloud app deploy app.yaml \cron.yaml

6. Open Google Cloud Logging and in the right dropdown select "GAE Application". If you don't see this option, it may mean that App Engine is still in the process of deploying.
7. Look for a log entry calling /_ah/start. If this entry isn't an error, then you're done deploying the App Engine app.

1. Ensure you're back the root of the repository (cd .., if you're coming from Step 2)
2. Deploy the sample hourly_job function to Google Cloud Functions

$ firebase deploy --only functions --project <FIREBASE_PROJECT_ID>

Warning: This will remove any existing functions you have deployed. If you have existing functions, move the example from functions/index.js into your project's index.js

We can verify that our function is wired up correctly by opening the Task Queue tab in AppEngine and clicking on Cron Jobs. Each of these jobs has a Run Now button next to it.

The sample functions we deployed only has one function: hourly_job. To trigger this job, let's hit the Run Now button for the /publish/hourly-tick job.

Then, go to your terminal and run...

$ firebase functions:log --project <FIREBASE_PROJECT_ID>

You should see a successful console.log from your hourly_job.

Your cron jobs will now "tick" along forever. As I mentioned above, you're not limited to the hourly-tick, daily-tick and weekly-tick that are included in the AppEngine app. You can add more scheduled functions by modifying the cron.yaml file and re-deploying.

Copyright 2017 Google Inc. All Rights Reserved.

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.