Fix the trace function for async functions.

[clokep]

I think this is the proper fix for the @trace decorator with async functions, but I'm not 100% sure.

I think there might be an issue open for some things missing from tracing, which could be this?

The diff should be better without whitespace changes.

[richvdh]

You've made this harder than it needs to be :).

No need to call __enter__/__exit__ manually. Just:

with scope:
    return await func(*args, **kwargs)

possibly with an except clause just to set_tag(tags.ERROR)

[clokep]

Yeah, I was copying and pasting from below. I can update both to actually use a context manager instead.

[clokep]

Ah, I see the Deferred case can't use the context manager easily, that's why it was that way. 👍

[clokep]

We could always assume that the non-coroutine case was an inlineDeferred, this seems to be what measure_func does:

synapse/synapse/util/metrics.py

Lines 64 to 87 in 39230d2

	def measure_func(name=None):
	def wrapper(func):
	block_name = func.__name__ if name is None else name
	if inspect.iscoroutinefunction(func):
	@wraps(func)
	async def measured_func(self, *args, **kwargs):
	with Measure(self.clock, block_name):
	r = await func(self, *args, **kwargs)
	return r
	else:
	@wraps(func)
	@defer.inlineCallbacks
	def measured_func(self, *args, **kwargs):
	with Measure(self.clock, block_name):
	r = yield func(self, *args, **kwargs)
	return r
	return measured_func
	return wrapper

[clokep]

@richvdh I had to add back to opentracing checks, see #7872 (comment)

[richvdh]

lgtm