Type error on version 0.8.0

[Guillaume Savary]

My pytest tests fails since I upgraded starlette_exporter to 0.8.0 (from 0.7.0).
I use FastAPI.

Here the error:

            labels = [method, path, status_code, self.app_name]
    
            self.request_count.labels(*labels).inc()
>           self.request_time.labels(*labels).observe(end - begin)
E           TypeError: unsupported operand type(s) for -: 'NoneType' and 'float'

venv/lib/python3.7/site-packages/starlette_exporter/middleware.py:105: TypeError

It seems that there are cases where end is never set.

The full trace:

venv/lib/python3.7/site-packages/requests/sessions.py:590: in post
    return self.request('POST', url, data=data, json=json, **kwargs)
venv/lib/python3.7/site-packages/starlette/testclient.py:431: in request
    json=json,
venv/lib/python3.7/site-packages/requests/sessions.py:542: in request
    resp = self.send(prep, **send_kwargs)
venv/lib/python3.7/site-packages/requests/sessions.py:655: in send
    r = adapter.send(request, **kwargs)
venv/lib/python3.7/site-packages/starlette/testclient.py:243: in send
    raise exc from None
venv/lib/python3.7/site-packages/starlette/testclient.py:240: in send
    loop.run_until_complete(self.app(scope, receive, send))
venv/lib/python3.7/site-packages/nest_asyncio.py:70: in run_until_complete
    return f.result()
/usr/lib/python3.7/asyncio/futures.py:178: in result
    raise self._exception
/usr/lib/python3.7/asyncio/tasks.py:223: in __step
    result = coro.send(None)
venv/lib/python3.7/site-packages/fastapi/applications.py:199: in __call__
    await super().__call__(scope, receive, send)
venv/lib/python3.7/site-packages/starlette/applications.py:112: in __call__
    await self.middleware_stack(scope, receive, send)
venv/lib/python3.7/site-packages/starlette/middleware/errors.py:181: in __call__
    raise exc from None
venv/lib/python3.7/site-packages/starlette/middleware/errors.py:159: in __call__
    await self.app(scope, receive, _send)

[Steve Hillier]

hi @elrik75 thanks for reporting an issue. Can you give me a little more info about your endpoint?

In hindsight initializing the end variable as None might not be a great idea; on the other hand I think 0 or a value from time.perf_counter() would silently give misleading results.

[Steve Hillier]

I published a simple fix in 0.8.1. Please let me know if this fixes your issue.

[Guillaume Savary]

Hi! Thanks a lot, my tests pass now without errors.
I've not checked the metric values yet. I'll post here if I see something weird on production.