[CentralOH] Django + Celery + RabbitMQ
Nick Albright
nick.albright at gmail.com
Wed Jul 20 18:27:26 CEST 2011
My pleasure! Yeah, most of my views use render_to_response(), I generally
only use render_to_string for returning ajax responses that need HTML. Very
handy. = )
And if you have a need, you can use the same view to do ajax and normal http
responses, you can just key off of request.is_ajax() like:
if request.is_ajax()
// Do ajax stuff, like calling render_to_string
else:
// Do the normal web stuff, calling render_to_response
If you have any more ajax/django Qs, ask away! :)
-Nick
On Wed, Jul 20, 2011 at 10:54 AM, coding.solo <coding.solo at gmail.com> wrote:
> Thanks, Nick! Being new to Django, I have built my views to
> render_to_response(). I like your example to get this over the wire using
> JSON with a customized response. As I see in your code, you are relying on
> Django to markup the results as opposed to letting JS do this -- that
> definitely steered me in a new direction. I am grasping this DRY principle,
> fondly. :) I haven't done any JSON with Django yet, so this provides a
> concrete example how to accomplish it. Thank you for your time and
> contribution, Nick!!
>
>
> Now just for that Celery part, and I think I'll be sitting pretty.
>
> Brandon
>
>
>
>
> On Wed, Jul 20, 2011 at 10:18 AM, Nick Albright <nick.albright at gmail.com>wrote:
>
>> Hello Brandon!
>>
>> I've never really worked with Celery or RabbitMQ (though, I want to!) so I
>> can't really address those issues, but I have done a bit of ajax and django,
>> so I can try to help out. (Uncertain based on your Qs if I can help, but I
>> prolly can't hurt! :)
>>
>> 1) Sorry, sounds like a Celery Q, I can't help there.
>> 2) I might be able to help here! = )
>>
>> So I assume you are doing some browser side ajax polling (using the
>> task_id returned by Celery) to a django view which in turn will query to see
>> if there are results to return. Once you get the list from celery in the
>> django view. I'd format the list to HTML (seen below) and return that to
>> the browser, which can then insert that in the umm.. div/list of the
>> browser. (I use jQuery for all my ajax and dom manipulation) So the django
>> side might look something like:
>>
>> def check_for_results( request, task_id = None ):
>> response = {}
>>
>> # Could be passing the task_id in the GET params
>> task_id = int( request.GET.get( 'task_id', task_id ) ) # Assumes
>> task_id is really an int. If not, don't cast it to one! :)
>>
>> results = CheckCeleryForResults( task_id ) # Whatever celery magic
>> goes here
>>
>> if results:
>> # Convert the list to HTML for display
>> response[ 'list' ] = render_to_string(
>> 'appname/inclues/ist_display.html',
>> {
>> 'results_list': results,
>> },
>> context_instance = RequestContext( request ) )
>> response[ 'done' ] = 1 # If you know there are more results
>> coming later, could make this 0
>> else:
>> response[ 'done' ] = 0
>>
>> return( HttpResponse( simplejson.dumps( response ),
>> mimetype='application/json' )
>>
>>
>> Note, I'm a huge fan of letting django format the HTML using a template,
>> as I can use that same template on initial page generation if I have any
>> list elements initially when the page is generated. It's DRY and all that.
>> :)
>>
>> And in your HTML, you have a call like:
>>
>>
>> <script language="javascript" type="text/javascript">
>> function CheckForResults( task_id ) {
>> $.getJSON( "{% url check_for_results %}",
>> { task_id: task_id },
>> function( json, textStatus ) {
>> // Hey! We got results! Let's show them to our
>> beloved user!
>> if ( json[ 'list' ] ) {
>> $('#results_list').append( json[ 'list'] );
>> }
>> // Looks like we aren't done, let's poll again
>> in a bit
>> if ( json[ 'done' ] and !json[ 'done' ] ) {
>> setTimeout( function() { CheckForResults(
>> task_id ); }, 5000 ); // Wait 5 seconds and try again
>> }
>> }
>> );
>> }
>> </script>
>>
>>
>> I hope that helps!
>> -Nick
>>
>>
>> On Wed, Jul 20, 2011 at 8:51 AM, coding.solo <coding.solo at gmail.com>wrote:
>>
>>> Hi all, I hope you guys can help me on this:
>>>
>>> I have a developing a Django app that processes many <reallyLongTask>.
>>> My current implementation to get everything up and running was to block for
>>> <reallyLongTask> and then deliver the results in a view. That works great,
>>> but was really long. Now I want to take it 2.0 with the auspicious notion
>>> of asynchronous back-end processing whilst polling with AJAX on the
>>> front-end to populate the results as they are ready. Currently, a
>>> <reallyLongTask> returns a list of lists. Instead of returning a list of
>>> lists, I want to factor out the enveloping list and just want to return
>>> lists.
>>>
>>> Now begins my questions. I have Celery successfully working with
>>> RabbitMQ. In my Django view, I execute my <reallyLongTask>.delay() and
>>> catch its AsyncResult. I get the AsyncResult.task_id over to the front-end
>>> browser so that it can poll this task.
>>>
>>> 1) In my AJAX Django view, how am I supposed to query the task with
>>> only this task_id?
>>> 2) Since my original view no longer returns a list of lists, what do
>>> you guys suggest I do to pass my *lists* back to the browser front-end
>>> when each individual one is ready? I would suspect RabbitMQ could handle
>>> such an exchange somehow, possibly even Celery. I am thinking I want to
>>> populate a list for the AJAX view to draw from when the front-end polls that
>>> view.
>>>
>>>
>>>
>>> Thanks all! Can't wait for my first PyOhio!
>>>
>>>
>>> Brandon Lorenz
>>>
>>> _______________________________________________
>>> CentralOH mailing list
>>> CentralOH at python.org
>>> http://mail.python.org/mailman/listinfo/centraloh
>>>
>>>
>>
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