Execute Backends using Cron in Google App Engine (Java)

Question

I have a Dynamic Backend setup on GAE which I want to run using cron every 15mins. The problem is cron requires a url that begins with "/". While a backend URL uses the following format: http://backendname.yourapp.appspot.com.

I've read in other forums that you could use fetchurl to call your backend but I don't think that's the ideal way. Because that would require you to make your backend publicly accessible.

According to google's documentation: http://code.google.com/appengine/docs/java/backends/overview.html#Public_and_Private_Backends

"Private backends can be accessed by application administrators, instances of the application, and by App Engine APIs and services (such as Task Queue tasks and Cron jobs) without any special configuration."

Has anybody got backends called by declaring it in cron.xml?

Answer 1

Use target tag to specify a backend in your cron.xml.

<?xml version="1.0" encoding="UTF-8"?>
<cronentries>
  <cron>
    <url>/long-task</url>
    <description></description>
    <schedule>every 30 minutes</schedule>
    <target>name-of-the-backend</target>
  </cron>
</cronentries>

Answer 2

urlfetch can be used to access internal-only URLs such as private backends - if that weren't possible, there'd be no way to communicate within your app! A better idea, though, might be to use the Task Queue, which can be configured to run tasks against a backend.