The App Engine Cron Service allows you to configure regularly scheduled tasksthat operate at defined times or regular intervals. These tasks are commonlyknown ascron jobs. These cron jobs are automatically triggered by theApp Engine Cron Service. For instance, you might use a cron job to sendout an email report on a daily basis, or to update some cached data every 10minutes, or refresh summary information once an hour.

A cron job makes a scheduled HTTPGET request to the specified endpoint in thesame app where the cron job is configured. The handler for that endpoint executesthe logic when it is called.

The App Engine Cron Service cannot be used to call web endpoints outside theApp Engine host app. It cannot be used to call App Engineendpoints from other apps besides the host app.

A cron job request is subject to the same limits as those forpush task queues.

Before you begin

To deploy or update schedules, your account requires one of the followingIAM roles:

• Owner
• Editor

You can set the permission on theIAM page in the Google Cloud console.

Creating a cron job

1. Create thecron.yaml file in the root directory of yourapplication (alongsideapp.yaml).

2. Add one or more<cron> entries to your file and define thenecessary elements for your job, including the required<url> and<schedule> elements.Review the cron.yaml syntax andoptionsfor more details about the elements of thecron.yaml file.

   The following example creates a basic cron job that runs daily:

   cron:-description:"daily summary job"url:/tasks/summarytarget:betaschedule:every24hours

   The target specification is optional and is the name of a service/version.If present, the target is prepended to your app's hostname, causing the jobto be routed to that service/version.If no target is specified, the job will run in the versions of thedefaultservice that are configured for traffic.

3. Create a handler for the cron job URL. The handler should execute any tasksthat you want scheduled. The handler should respond with an HTTP status codebetween 200 and 299 (inclusive) to indicate success. Other status codes canbe returned and can be used toretry the cron job.

Testing cron jobs in the development server

The local development server doesn't automatically run your cron jobs. You canmake requests directly to your cron job's URL to test your functionality. Youcan use your local cron or scheduled tasks interface to trigger the URLs of yourjobs withcurl or a similar tool.

You can use the admin interface of the local development server toview your cron jobs athttp://localhost:8000/cron.

Retrying cron jobs that fail

If a cron job's request handler returns a status code that is not in the range200–299 (inclusive) App Engine considers the job to have failed. By default,failed jobs are not retried unless a 503 status code is returned, in which caseit is retried every minute until it succeeds or returns a 200-299 status code.

To set failed jobs to be retried:

1. Include aretry_parameters block in yourcron.yaml file.

2. Choose and set theretry parameters in theretry_parameters block.

   For example, this samplecron.yaml file contains a single cron job that isconfigured to retry up to five times (the default) with a starting backoffof 2.5 seconds that doubles each time.

   cron:-description:"retry demo"url:/retryschedule:every10minsretry_parameters:min_backoff_seconds:2.5max_doublings:5

Learn more about the cron retryoptions.

Deploying cron jobs

To deploy the cron jobs specified in yourcron.yaml configuration file,run the following command:

gcloudappdeploycron.yaml

Deleting all cron jobs

To delete all cron jobs:

1. Edit the contents of thecron.yaml file to:

   cron:

2. Deploy thecron.yaml file to App Engine.

Securing URLs for cron

A cron handler is just a normal handler defined inapp.yaml. You can preventusers from accessing URLs used by scheduled tasks by restricting access toadministrator accounts. Scheduled tasks can access admin-only URLs. You canrestrict a URL by addinglogin: admin to the handler configuration inapp.yaml.

An example might look like this inapp.yaml:

runtime:python27api_version:1handlers:-url:/report/weeklyscript:reports.applogin:admin

To test a cron job, sign in as an administrator and visit the URL of the handlerin your browser.

Requests from the Cron Service will also contain a HTTP header:

X-Appengine-Cron:true

TheX-Appengine-Cron header is set internally by App Engine. If yourrequest handler finds this header it can trust that the request is a cronrequest. If the header is present in an external user request to your app, itis stripped, except for requests from logged in administrators of theapplication, who are allowed to set the header for testing purposes.

App Engine issues Cron requests from the IP address0.1.0.2. For Cron jobs created with older gcloud versions (earlier than326.0.0), Cron requests will come from0.1.0.1.

Calling Google Cloud Endpoints

You cannot specify aGoogle Cloud Endpoint intheurl field of a cron job.If you want your cron job to call a Google Cloud Endpoint,issue a request to a target that is served by a handler inyour app, and call the endpoint class and method from the handler code.

Viewing cron jobs in the Google Cloud console

You can view scheduled cron jobs inCloud Scheduler'sApp Engine Cron Jobstab.

You can alsoview logs to see when cron jobs were added or removed.

Learn more

See detailed information about defining cron jobs in thecron.yamlReference.