Samples with response_time None crashes stats.py

Certain async protocols/clients (like websockets, MQ etc) dont really have a response time. They should be able to report a None response time. Using zero is not good enough, because a test may contain a mix of synchronous requests (like HTTP) and async, and we dont want to “taint” the average response time with zeroes.

from locust import HttpLocust, task, TaskSet
from locust.events import request_success

class UserBehavior(TaskSet):
    @task
    def my_task(self):
        request_success.fire(request_type="foo", name="bar", response_time=None, response_length=0)


class MyHttpLocust(HttpLocust):
    task_set = UserBehavior

Result:

[2019-09-22 09:57:13,877] lafp-mac-JG5J.int.svenskaspel.se/ERROR/stderr: Traceback (most recent call last):
  File "/Users/lafp/git/locust/locust/core.py", line 361, in run
    self.execute_next_task()
  File "/Users/lafp/git/locust/locust/core.py", line 387, in execute_next_task
    self.execute_task(task["callable"], *task["args"], **task["kwargs"])
  File "/Users/lafp/git/locust/locust/core.py", line 399, in execute_task
    task(self, *args, **kwargs)
  File "/Users/lafp/git/locust-plugins/examples/foo.py", line 10, in my_task
    request_success.fire(request_type="foo", name="bar", response_time=None, response_length=0)
  File "/Users/lafp/git/locust/locust/events.py", line 34, in fire
    handler(**kwargs)
  File "/Users/lafp/git/locust/locust/stats.py", line 559, in on_request_success
    global_stats.log_request(request_type, name, response_time, response_length)
  File "/Users/lafp/git/locust/locust/stats.py", line 93, in log_request
    self.total.log(response_time, content_length)
  File "/Users/lafp/git/locust/locust/stats.py", line 239, in log
    self._log_response_time(response_time)
  File "/Users/lafp/git/locust/locust/stats.py", line 250, in _log_response_time
    self.total_response_time += response_time
TypeError: unsupported operand type(s) for +=: 'int' and 'NoneType'

[heyman]

I agree that it makes sense to be able to report requests without response times so that they wouldn’t taint the stats for ordinary requests.

The #1088 PR should have tests. I’m a little bit concerned that the changes could have unintended effects since the code up until now have always assumed that each request has a response time. That might be an unfounded concern though, but in any case, I think these changes should come with multiple tests where non-response-time requests are made both by themselves, as well as together with “normal” requests that have a response time.

[cyberw]

I’ve fixed the issues with calculating averages and median.