Applications do work in response to external stimuli: user requests, incoming email and XMPP messages, HTTP requests sent by a script on your computer. And while task queues can be used to trigger events across a period of time, a task must be enqueued by application code before anything happens.
Sometimes you want an application to do something “on its own.” For instance, an app may need to send nightly email reports of the day’s activity, or fetch new headlines from a news service. For this purpose, App Engine lets you specify a schedule of tasks to perform on a regular basis. In the App Engine API, scheduled tasks are also known as “cron jobs,” named after a similar feature in the Unix operating system.
A scheduled task consists of a URL path to call and a description of the recurring times of the day, week, or month at which to call it. It can also include a description, which is displayed in the Administration Console and other reports of the schedule.
To execute a scheduled task, App Engine calls the URL path using an empty GET request. A scheduled task cannot be configured with parameters, headers, or a different HTTP method. If you need something more complicated, you can do it in the code for the request handler mapped to the scheduled task’s URL path.
As with task queue handlers, you can secure the URL path by restricting it to application developers in the frontend configuration. The system can call such URL paths to execute scheduled tasks.
The HTTP request ...