Django broken pipe error

[roma]

On Wednesday, December 7, 2016 at 6:15:41 PM UTC+1, justin walters wrote:
> On Wed, Dec 7, 2016 at 1:08 AM, <dr.roman.graf at gmail.com> wrote:
> 
> > Thank you Justin,
> >
> > I'm on the dev server and should present results in this way.
> >
> > Yes, I use manage.py runserver --insecure to start the server (from
> > PyCharm).
> >
> > My views.py call:
> >
> > @detail_route(methods=['post'], permission_classes=[permissions.AllowAny])
> > def export_report(request):
> >     body_unicode = request.body.decode('utf-8')
> >     body_str = body_unicode.encode('ascii','ignore')
> >     attr_list = body_str.split('&')
> >     attr_dict = {}
> >     if (len(attr_list) > 0):
> >         for attr in attr_list:
> >            ...
> >            key = key_value_pair[0]
> >            attr_dict[key] = key_value_pair[1]
> >     trend = trends.calculate_trend(
> >         attr_dict['search_phrase']
> >         , attr_dict['time_from']
> >         , attr_dict['time_to']
> >         , attr_dict['time_scale']
> >     )
> >     attr_dict['trend'] = trend
> >     res = str(json.dumps(attr_dict))
> >     return HttpResponse(res, content_type="text/plain; charset=utf-8")
> >
> > and trend calculation in trends.py with database calls:
> >
> > def calculate_trend(query_phrase, time_from, time_to, time_scale):
> >     # check in database if trend already exists
> >     try:
> >         db_trend = Trend.objects.get(pk=query_phrase)
> >         if db_trend.from_time.strftime("%Y-%m-%d") == time_from \
> >                 and db_trend.to_time.strftime("%Y-%m-%d") == time_to \
> >                 and db_trend.granularity == time_scale:
> >             logger.info("trend already exists.")
> >             existing_trend_dict = ast.literal_eval(db_trend.content)
> >             return existing_trend_dict
> >     except Trend.DoesNotExist:
> >         logger.info("It is a new trend search.")
> >     trend_dict = {}
> >     start_time = pd.Timestamp(value[0])
> >     end_time = pd.Timestamp(value[-1])
> >     freq = ... get frequency using pandas lib
> >     trend_dict[key] = freq
> >     json_trend_content = trend_dict_to_sorted_json_str(trend_dict)
> >     trend = Trend(
> >         phrase=query_phrase,
> >         content=json_trend_content,
> >         from_time=time_from,
> >         to_time=time_to,
> >         granularity=time_scale,
> >     )
> >     if trend is not None:
> >         try:
> >             db_trend = Trend.objects.get(pk=query_phrase)
> >             db_trend.delete()
> >             logger.info("delete old trend: %s. " % trend)
> >         except Trend.DoesNotExist:
> >             logger.info("create trend: %s. " % trend)
> >         trend.save()
> >     return trend_dict
> >
> > Thank you in advance!
> >
> > Roman
> > --
> > https://mail.python.org/mailman/listinfo/python-list
> >
> 
> 
> It looks like you can probably get rid of the try/except block at the end
> of the calculate_trend
> method as any existing Trend object will have already been caught in the
> first try/except block.
> 
> >From what I'm reading here:
> http://stackoverflow.com/questions/11866792/how-to-prevent-errno-32-broken-pipe
> ,
> this issue can be caused by the client closing the connection before
> sendall() finishes writing. Can you estimate
> how long it takes for a request to this endpoint takes to resolve? If it's
> a long time(maybe due to the pandas call?),
> your browser/client may be timing out. It could be because it takes a while
> for the Db to find an existing Trend object
> as well.
> 
> I can't give you any advice on how to fix it exactly, but I can tell you
> what the problem is: The client is closing the
> connection before socket.sendall() has finished writing to the socket. My
> guess is that the calculate_trend() method
> takes a long time to complete and the client is timing out.

Thanks Justin,

I believe, the whole database story has no influence on the broken pipe error. I've commented out the whole block and leave only return line:
return HttpResponse(res, content_type="text/plain; charset=utf-8") 
The error is still present. And I have no influence on that.

I call python from js client:

    var newTrendReport = new App.TrendReport();
    newTrendReport.set('search_phrase', search_phrase);
    newTrendReport.set('time_from', time_from);
    newTrendReport.set('time_to', time_to);
    newTrendReport.set('time_scale', time_scale);
    newTrendReport.set('category', category);
    newTrendReport.startExport(

        function(response){
            console.log("Successfully calculated trend report.");
    		App.trendPage = new App.TrendPageView();
    		App.trendPage.render(response);
        },
    );

go throw:

    App.TrendReport = Backbone.Model.extend({
        urlRoot: "/api/trend_reports/",
        defaults: {
            search_phrase: "",
            time_from: "",
            time_to: "",
            time_scale: "",
            category: ""
        },

        startExportSuffix: "/export_report/",

        startExport: function( successCallback, errorCallback ) {
            console.log("start trend calculation");
            var that = this;
            var ajaxUrl = this.startExportSuffix;
            var options = {
                method: "POST",
                data: this.attributes,
                contentType: "application/json;charset=UTF-8",
                dataType: "json",

                error: errorCallback,
                success: successCallback
            };
            console.log("start trend export sync");
            App.ajax(ajaxUrl, options);
        }

    });

and come in export_report method.

My urls.py:

    url(r'^export_report', ensure_csrf_cookie(views.export_report), name="export_report"),