Oh yeah, I guessed the *--backends* flag on *appcfg.py update *was
intended as a replacement for running a separate backends update each time.
Steve
On 11-09-09 06:22 PM, Rishi Arora wrote:
Found my problem. Looks like I must execute that appcfg.py update
backends command each time I make a code change. It seems obvious
now, but of course, it never occurred to me! I'm all good now, even
with countdown set to 0, and tasqueue target set to either
instance.backend_name or just backend_name.
It also might seem silly that I'm making my backend queue up requests
for itself (in an attempt to break up requests), when in fact it could
process the whole big request inline in one shot. But its actually
common code that might also get executed by a front-end in some
circumstances. I should look into a run-time condition that I can use
to determine whether I'm in the context of a front-end or a backend,
and queue up requests to myself only for front-end instances. Do you
know if there's a way to do that?
Thanks for your help!
Regards
-Rishi
On Fri, Sep 9, 2011 at 4:34 PM, Rishi Arora <rishi.ar...@ship-rack.com
<mailto:rishi.ar...@ship-rack.com>> wrote:
I came across this
(http://code.google.com/appengine/docs/python/taskqueue/overview-push.html#Push_Queues_and_Backends).
Which suggests that I should be able to use a specific backend
instance. Not only was the backend started (really, enabled), but
it was up and running too, from serving up a request recently. In
fact, I'm enqueueing the taskqueue request from the backend itself
(the backend logs prove it too). I tried your method too (using
just the backend name, and no instance prefix), and that didn't
work either. The only difference is that I'm not passing any
"params" parameter in the taskqueue.add() call. The request is
just meant to be a trigger and does not carry any data. Perhaps
the app engine scheduler thinks that my backend is busy (cause it
was processing the current request which enqueued the new
taskqueue request), and that causes it to send the request to a
front-end instance. Maybe I should send the taskqueue rquest with
a "countdown" set to a comfortable 10 seconds or something.
Here's the snippet from the link above:
Push tasks typically must finish execution within 10 minutes. If
you have push tasks that require more time or computing resources
to process, you can use App Engine Backends to process these tasks
outside of the normal limits of App Engine applications. Backends
are addressable. When you create the push task, all you need to do
is address it to the URL of the backend you wish to process it.
The following code sample demonstrates how to create a push task
addressed to an instance 1 of a backend named backend1:
from google.appengine.api import taskqueue
...
def post(self):
key = self.request.get('key')
# Add the task to the default queue.
taskqueue.add(url='/path/to/my/worker/', params={'key':
key}, target='1.backend1')
On Fri, Sep 9, 2011 at 4:10 PM, Steve Sherrie
<st...@wasteofpaper.com <mailto:st...@wasteofpaper.com>> wrote:
I'm able to direct tasks to the backends using the *target*
arg as in your example. And the backend state is 'start' when
you're trying this?
Are you directing toward a specific backend instance
(/N.backend_name/) or just to /backend_name/? I am doing the
latter.
Steve
On 11-09-09 05:00 PM, Rishi Arora wrote:
Thanks. Yes that worked for me. It just seems that backend
documentation isn't very intuitive. I couldn't tell from any
of the online docs that simply adding a backend to
backends.yaml won't configure a backend for you. It won't
show up in the backends section of the admin console until
you execute appcfg.py update backends.
Another non-intuitive behavior - probably only for dynamic
backends. The admin console has a start/stop button. But
obviously, if you hit start, the dynamic backend won't
actually start. That's clear from the documentation. But,
if you hit "stop", it almost looks like that the backend is
made inaccessbile. It won't process requests, and it won't
automatically restart on the next request. You have to hit
the "start" button first. I think for dynamic backends that
button should read "enable/disable".
Now the next thing I'm trying to get to work is sending a
backend a request from a task queue. I'm using the default
task queue to do this, and simply doing this doesn't work (a
front-end instance processes the taskqueue request):
taskqueue.add(url=[relative path to request handler],
method='POST', target=[backend name from app.yaml])
Modifying the above statement to specify the entire URL for
the backend in the "target" parameter does not help either -
the taskqueue request is still processed by a front-end
instance. I also tried just getting rid of the "target"
parameter, and specifying the entire url in the "url"
parameter i.e.
url='https://backend.appid.appspot.com/path/to/requesthandler'.
And even that did not help. I fear forcing backends to
process cron entries defined with a full URL like above won't
do the trick either.
So is there no way to force a backend to process a request?
On Fri, Sep 9, 2011 at 3:45 PM, Steve Sherrie
<st...@wasteofpaper.com <mailto:st...@wasteofpaper.com>> wrote:
Also, you can do...
*
*
*appcfg.py update **--backends your_app*
*
*
*
*
Steve
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