Executing tasks on a remote web server¶

If you need to call into another language, framework or similar, you can do so by using HTTP tasks.

The HTTP tasks (or REST task) uses a simple REST+JSON scheme to take arguments and return results, the scheme to call a task is:

GET http://example.com/mytask/?arg1=a,arg2=b,arg3=c

The web page should then return a response in the following format if the execution was successful:

{"status": "success", "retval": ....}

or in the following format if there was an error:

{"status": "failure": "reason": "Invalid moon alignment."}

With this information we can define a simple task in Django:

from django.http import HttpResponse
from anyjson import serialize


def multiply(request):
    x = int(request.GET["x"])
    y = int(request.GET["y"])
    result = x * y
    response = {"status": "success", "retval": result}
    return HttpResponse(serialize(response), mimetype="application/json")

I’m sure you’ll be able to port this scheme to any language/framework. New examples and libraries are very welcome!

To execute the task you use celery.task.rest.RESTProxyTask:

>>> from celery.task import RESTProxyTask
>>> res = RESTProxyTask.delay("http://example.com/multiply", x=10, y=10)
>>> res.get()
100

In your celeryd.log file you should see the task being processed:

[INFO/MainProcess] Task celery.task.rest.RESTProxyTask
    [f2cc8efc-2a14-40cd-85ad-f1c77c94beeb] processed: 100

Since applying tasks can also simply be done via the web and the celery.views.apply view, executing tasks from other languages should be a no-brainer.