diff options
| -rw-r--r-- | synapse/util/logcontext.py | 60 | ||||
| -rw-r--r-- | tests/util/test_logcontext.py | 66 |
2 files changed, 93 insertions, 33 deletions
diff --git a/synapse/util/logcontext.py b/synapse/util/logcontext.py index 01ac71e53e..e086e12213 100644 --- a/synapse/util/logcontext.py +++ b/synapse/util/logcontext.py @@ -302,7 +302,7 @@ def preserve_fn(f): def run_in_background(f, *args, **kwargs): """Calls a function, ensuring that the current context is restored after return from the function, and that the sentinel context is set once the - deferred returned by the funtion completes. + deferred returned by the function completes. Useful for wrapping functions that return a deferred which you don't yield on (for instance because you want to pass it to deferred.gatherResults()). @@ -320,24 +320,31 @@ def run_in_background(f, *args, **kwargs): # by synchronous exceptions, so let's turn them into Failures. return defer.fail() - if isinstance(res, defer.Deferred) and not res.called: - # The function will have reset the context before returning, so - # we need to restore it now. - LoggingContext.set_current_context(current) - - # The original context will be restored when the deferred - # completes, but there is nothing waiting for it, so it will - # get leaked into the reactor or some other function which - # wasn't expecting it. We therefore need to reset the context - # here. - # - # (If this feels asymmetric, consider it this way: we are - # effectively forking a new thread of execution. We are - # probably currently within a ``with LoggingContext()`` block, - # which is supposed to have a single entry and exit point. But - # by spawning off another deferred, we are effectively - # adding a new exit point.) - res.addBoth(_set_context_cb, LoggingContext.sentinel) + if not isinstance(res, defer.Deferred): + return res + + if res.called and not res.paused: + # The function should have maintained the logcontext, so we can + # optimise out the messing about + return res + + # The function may have reset the context before returning, so + # we need to restore it now. + ctx = LoggingContext.set_current_context(current) + + # The original context will be restored when the deferred + # completes, but there is nothing waiting for it, so it will + # get leaked into the reactor or some other function which + # wasn't expecting it. We therefore need to reset the context + # here. + # + # (If this feels asymmetric, consider it this way: we are + # effectively forking a new thread of execution. We are + # probably currently within a ``with LoggingContext()`` block, + # which is supposed to have a single entry and exit point. But + # by spawning off another deferred, we are effectively + # adding a new exit point.) + res.addBoth(_set_context_cb, ctx) return res @@ -354,9 +361,18 @@ def make_deferred_yieldable(deferred): (This is more-or-less the opposite operation to run_in_background.) """ - if isinstance(deferred, defer.Deferred) and not deferred.called: - prev_context = LoggingContext.set_current_context(LoggingContext.sentinel) - deferred.addBoth(_set_context_cb, prev_context) + if not isinstance(deferred, defer.Deferred): + return deferred + + if deferred.called and not deferred.paused: + # it looks like this deferred is ready to run any callbacks we give it + # immediately. We may as well optimise out the logcontext faffery. + return deferred + + # ok, we can't be sure that a yield won't block, so let's reset the + # logcontext, and add a callback to the deferred to restore it. + prev_context = LoggingContext.set_current_context(LoggingContext.sentinel) + deferred.addBoth(_set_context_cb, prev_context) return deferred diff --git a/tests/util/test_logcontext.py b/tests/util/test_logcontext.py index 4850722bc5..ad78d884e0 100644 --- a/tests/util/test_logcontext.py +++ b/tests/util/test_logcontext.py @@ -36,24 +36,28 @@ class LoggingContextTestCase(unittest.TestCase): yield sleep(0) self._check_test_key("one") - def _test_preserve_fn(self, function): + def _test_run_in_background(self, function): sentinel_context = LoggingContext.current_context() callback_completed = [False] - @defer.inlineCallbacks - def cb(): + def test(): context_one.request = "one" - yield function() - self._check_test_key("one") + d = function() - callback_completed[0] = True + def cb(res): + self._check_test_key("one") + callback_completed[0] = True + return res + d.addCallback(cb) + + return d with LoggingContext() as context_one: context_one.request = "one" # fire off function, but don't wait on it. - logcontext.preserve_fn(cb)() + logcontext.run_in_background(test) self._check_test_key("one") @@ -80,20 +84,30 @@ class LoggingContextTestCase(unittest.TestCase): # test is done once d2 finishes return d2 - def test_preserve_fn_with_blocking_fn(self): + def test_run_in_background_with_blocking_fn(self): @defer.inlineCallbacks def blocking_function(): yield sleep(0) - return self._test_preserve_fn(blocking_function) + return self._test_run_in_background(blocking_function) - def test_preserve_fn_with_non_blocking_fn(self): + def test_run_in_background_with_non_blocking_fn(self): @defer.inlineCallbacks def nonblocking_function(): with logcontext.PreserveLoggingContext(): yield defer.succeed(None) - return self._test_preserve_fn(nonblocking_function) + return self._test_run_in_background(nonblocking_function) + + def test_run_in_background_with_chained_deferred(self): + # a function which returns a deferred which looks like it has been + # called, but is actually paused + def testfunc(): + return logcontext.make_deferred_yieldable( + _chained_deferred_function() + ) + + return self._test_run_in_background(testfunc) @defer.inlineCallbacks def test_make_deferred_yieldable(self): @@ -119,6 +133,22 @@ class LoggingContextTestCase(unittest.TestCase): self._check_test_key("one") @defer.inlineCallbacks + def test_make_deferred_yieldable_with_chained_deferreds(self): + sentinel_context = LoggingContext.current_context() + + with LoggingContext() as context_one: + context_one.request = "one" + + d1 = logcontext.make_deferred_yieldable(_chained_deferred_function()) + # make sure that the context was reset by make_deferred_yieldable + self.assertIs(LoggingContext.current_context(), sentinel_context) + + yield d1 + + # now it should be restored + self._check_test_key("one") + + @defer.inlineCallbacks def test_make_deferred_yieldable_on_non_deferred(self): """Check that make_deferred_yieldable does the right thing when its argument isn't actually a deferred""" @@ -132,3 +162,17 @@ class LoggingContextTestCase(unittest.TestCase): r = yield d1 self.assertEqual(r, "bum") self._check_test_key("one") + + +# a function which returns a deferred which has been "called", but +# which had a function which returned another incomplete deferred on +# its callback list, so won't yet call any other new callbacks. +def _chained_deferred_function(): + d = defer.succeed(None) + + def cb(res): + d2 = defer.Deferred() + reactor.callLater(0, d2.callback, res) + return d2 + d.addCallback(cb) + return d |