title: Django drf requests seem to be restarting when taking a long time
body: <p>I'm using Django with DRF and I have a viewset that writes info to a csv file and then sends the link to the user.</p>
  
  <p>The function works correctly when the data retrieved is not too big, so when the response time is reasonable everything works ok.</p>
  
  <p>The problem is when the request takes a longer time. It seems like it simply restarts from the request call all by itself</p>
  
  <pre><code>    def get_operations(self, request):
          logger.info("Starting export request...")
     #[...business logic to retrive the data ...]
          file_url = settings.MEDIA_PREFIX_PATH + file_path
          logger.info("Saving response in %s", file_absolute_path)
          f = open(file_absolute_path, "w+")
          all_operations = operations.all()
          i = 0
          for operation in all_operations:
              i = i + 1
              #code to show progress in the log
              if (i / len(all_operations)*1000) % 5 == 0:
                  logger.info("Progress:  %d ", (i / len(all_operations)*100))
  
              f.write("%s,%d,%d,%d,%s,%s\n" % (operation.datetime, operation.amount, operation.field2, operation.field3, operation.field5, operation.field6))
          logger.info("Response saved, sending link %s", file_url)
          return Response(file_url)
  </code></pre>
  
  <p>In the log, this is what I'm getting </p>
  
  <pre><code>INFO 2018-11-26 11:23:33,525 Starting export request...
  INFO 2018-11-26 11:23:34,223 Response retrieved : 17010 records
  INFO 2018-11-26 11:23:34,225 Saving response in /tmp/generated_csv/1543231414.2250094.csv
  INFO 2018-11-26 11:23:42,825 Progress:  10 
  INFO 2018-11-26 11:23:51,161 Progress:  20 
  INFO 2018-11-26 11:23:59,072 Progress:  30 
  INFO 2018-11-26 11:24:07,694 Starting export request...
  INFO 2018-11-26 11:24:08,346 Response retrieved : 17010 records
  INFO 2018-11-26 11:24:08,348 Saving response in /tmp/generated_csv/1543231448.3486001.csv
  INFO 2018-11-26 11:24:16,653 Progress:  10 
  INFO 2018-11-26 11:24:24,271 Progress:  20 
  INFO 2018-11-26 11:24:32,248 Progress:  30 
  INFO 2018-11-26 11:24:42,573 Starting export request...
  INFO 2018-11-26 11:24:44,101 Response retrieved : 17010 records
  INFO 2018-11-26 11:24:44,109 Saving response in /tmp/generated_csv/1543231484.1097722.csv
  INFO 2018-11-26 11:24:55,092 Progress:  10 
  INFO 2018-11-26 11:25:04,131 Progress:  20 
  INFO 2018-11-26 11:25:11,242 Progress:  30 
  INFO 2018-11-26 11:25:16,801 Starting export request...
  INFO 2018-11-26 11:25:17,499 Response retrieved : 17010 records
  INFO 2018-11-26 11:25:17,501 Saving response in /tmp/generated_csv/1543231517.5013359.csv
  </code></pre>
  
  <p>I'm sure that the issue is not from the client side, because i also tried it with postman.</p>
  
  <p>I just don't understand what can cause the request to be called all by itself.</p>
  
  <p>Thanks</p>