Question

On my django app I have a report (a csv download) that can take some time to run. When a user runs the report they are redirected to a ‘processing’ page where a javascript function checks the server every second to see if the csv has been created (the file name is included in the HttpResponse object).

What I’m looking for is a way of identifying the thread that’s creating the csv. That way I can add an estimated_time_to_completion attribute to the thread, and include this info in the holding page. In fact I could stop checking for the existance of the (unlocked) csv – I could just ask the thread if it’s finished.

My csv building thread looks something like –

class CsvBuilder(threading.Thread):

    def __init__(self, file_name, parameters)
        self.file_name = file_name
        self.parameters = parameters
        threading.Thread.__init__(self)

    def run():
        # ...
        file = open(self.file_name, 'wb')
        writer = csv.writer(file)
        for patient in patients:
            writer.writerow('some data')
            self.time_remaining = # a timedelta object
        file.close()

And then my django requests will look something like –

def create_csv(request):
    '''
    Standard django view to create a csv
    '''
    # get filename and parameters from request
    thread = CsvBuilder (file_name, parameters)
    return render_to_response('processing.html', {"thread_id": thread.thread_id})

def check_progress(request):
    '''
    An ajax call to check the progress on a report
    '''
    thread_id = requst.GET['thread_id']
    # find the thread 
    return HttpResponse(thread.time_remaining)

Is this possible? Or should I be going about this a different way?

Answer 1

I’d suggest you have your writer function update a memcached key/value for time_remaining calculations.

If it were me, I’d have probably used Celery for the long running job, starting a thread from django seems like it could have pitfalls, but nothing specific is springing to mind.