From 9255a6cb17716c022ebae1dbe9c142b78ca86ea7 Mon Sep 17 00:00:00 2001 From: Richard van der Hoff Date: Fri, 27 Apr 2018 11:07:40 +0100 Subject: Improve exception handling for background processes There were a bunch of places where we fire off a process to happen in the background, but don't have any exception handling on it - instead relying on the unhandled error being logged when the relevent deferred gets garbage-collected. This is unsatisfactory for a number of reasons: - logging on garbage collection is best-effort and may happen some time after the error, if at all - it can be hard to figure out where the error actually happened. - it is logged as a scary CRITICAL error which (a) I always forget to grep for and (b) it's not really CRITICAL if a background process we don't care about fails. So this is an attempt to add exception handling to everything we fire off into the background. --- synapse/util/logcontext.py | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'synapse/util/logcontext.py') diff --git a/synapse/util/logcontext.py b/synapse/util/logcontext.py index d59adc236e..d6587e4409 100644 --- a/synapse/util/logcontext.py +++ b/synapse/util/logcontext.py @@ -305,7 +305,12 @@ def run_in_background(f, *args, **kwargs): deferred returned by the funtion completes. Useful for wrapping functions that return a deferred which you don't yield - on. + on (for instance because you want to pass it to deferred.gatherResults()). + + Note that if you completely discard the result, you should make sure that + `f` doesn't raise any deferred exceptions, otherwise a scary-looking + CRITICAL error about an unhandled error will be logged without much + indication about where it came from. """ current = LoggingContext.current_context() res = f(*args, **kwargs) -- cgit 1.4.1