From 791a8c559bf4ea984637c047fad7d6097e34ce99 Mon Sep 17 00:00:00 2001 From: Erik Johnston Date: Thu, 10 Oct 2019 11:53:57 +0100 Subject: [PATCH] Add coments --- synapse/util/patch_inline_callbacks.py | 30 +++++++++++++++++++++----- 1 file changed, 25 insertions(+), 5 deletions(-) diff --git a/synapse/util/patch_inline_callbacks.py b/synapse/util/patch_inline_callbacks.py index 5ef7190b1..b518dae25 100644 --- a/synapse/util/patch_inline_callbacks.py +++ b/synapse/util/patch_inline_callbacks.py @@ -107,6 +107,19 @@ def do_patch(): def _check_yield_points(f, changes, start_context): """Wraps a generator that is about to be passed to defer.inlineCallbacks checking that after every yield the log contexts are correct. + + Its perfectly valid for log contexts to change within a function, e.g. due + to new Measure blocks, so such changes are added to the given `changes` + list instead of triggering an exception. + + Args: + f: generator function to wrap + changes (list[str]): A list of strings detailing how the contexts + changed within a function. + start_context (LoggingContext): The initial context we're expecting + + Returns: + function """ from synapse.logging.context import LoggingContext @@ -131,6 +144,10 @@ def _check_yield_points(f, changes, start_context): # This happens when the context is lost sometime *after* the # final yield and returning. E.g. we forgot to yield on a # function that returns a deferred. + # + # We don't raise here as its perfectly valid for contexts to + # change in a function, as long as it sets the correct context + # on resolving (which is checked separately). err = ( "Function %r returned and changed context from %s to %s," " in %s between %d and end of func" @@ -143,14 +160,14 @@ def _check_yield_points(f, changes, start_context): ) ) changes.append(err) - # raise Exception(err) return getattr(e, "value", None) frame = gen.gi_frame if isinstance(d, defer.Deferred) and not d.called: # This happens if we yield on a deferred that doesn't follow - # the log context rules without wrappin in a `make_deferred_yieldable` + # the log context rules without wrappin in a `make_deferred_yieldable`. + # We raise here as this should never happen. if LoggingContext.current_context() is not LoggingContext.sentinel: err = ( "%s yielded with context %s rather than sentinel," @@ -162,8 +179,7 @@ def _check_yield_points(f, changes, start_context): frame.f_code.co_filename, ) ) - changes.append(err) - # raise Exception(err) + raise Exception(err) try: result = yield d @@ -171,10 +187,15 @@ def _check_yield_points(f, changes, start_context): result = Failure(e) if LoggingContext.current_context() != expected_context: + # This happens because the context is lost sometime *after* the # previous yield and *after* the current yield. E.g. the # deferred we waited on didn't follow the rules, or we forgot to # yield on a function between the two yield points. + # + # We don't raise here as its perfectly valid for contexts to + # change in a function, as long as it sets the correct context + # on resolving (which is checked separately). err = ( "%s changed context from %s to %s, happened between lines %d and %d in %s" % ( @@ -187,7 +208,6 @@ def _check_yield_points(f, changes, start_context): ) ) changes.append(err) - # raise Exception(err) expected_context = LoggingContext.current_context()