diff --git a/synapse/util/async.py b/synapse/util/async.py
index bb252f75d7..0fd5b42523 100644
--- a/synapse/util/async.py
+++ b/synapse/util/async.py
@@ -203,7 +203,26 @@ class Linearizer(object):
except:
logger.exception("Unexpected exception in Linearizer")
- logger.info("Acquired linearizer lock %r for key %r", self.name, key)
+ logger.info("Acquired linearizer lock %r for key %r", self.name,
+ key)
+
+ # if the code holding the lock completes synchronously, then it
+ # will recursively run the next claimant on the list. That can
+ # relatively rapidly lead to stack exhaustion. This is essentially
+ # the same problem as http://twistedmatrix.com/trac/ticket/9304.
+ #
+ # In order to break the cycle, we add a cheeky sleep(0) here to
+ # ensure that we fall back to the reactor between each iteration.
+ #
+ # (There's no particular need for it to happen before we return
+ # the context manager, but it needs to happen while we hold the
+ # lock, and the context manager's exit code must be synchronous,
+ # so actually this is the only sensible place.
+ yield run_on_reactor()
+
+ else:
+ logger.info("Acquired uncontended linearizer lock %r for key %r",
+ self.name, key)
@contextmanager
def _ctx_manager():
@@ -211,7 +230,8 @@ class Linearizer(object):
yield
finally:
logger.info("Releasing linearizer lock %r for key %r", self.name, key)
- new_defer.callback(None)
+ with PreserveLoggingContext():
+ new_defer.callback(None)
current_d = self.key_to_defer.get(key)
if current_d is new_defer:
self.key_to_defer.pop(key, None)
diff --git a/synapse/util/logformatter.py b/synapse/util/logformatter.py
new file mode 100644
index 0000000000..cdbc4bffd7
--- /dev/null
+++ b/synapse/util/logformatter.py
@@ -0,0 +1,51 @@
+# -*- coding: utf-8 -*-
+# Copyright 2017 New Vector Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+import StringIO
+import logging
+import traceback
+
+
+class LogFormatter(logging.Formatter):
+ """Log formatter which gives more detail for exceptions
+
+ This is the same as the standard log formatter, except that when logging
+ exceptions [typically via log.foo("msg", exc_info=1)], it prints the
+ sequence that led up to the point at which the exception was caught.
+ (Normally only stack frames between the point the exception was raised and
+ where it was caught are logged).
+ """
+ def __init__(self, *args, **kwargs):
+ super(LogFormatter, self).__init__(*args, **kwargs)
+
+ def formatException(self, ei):
+ sio = StringIO.StringIO()
+ (typ, val, tb) = ei
+
+ # log the stack above the exception capture point if possible, but
+ # check that we actually have an f_back attribute to work around
+ # https://twistedmatrix.com/trac/ticket/9305
+
+ if tb and hasattr(tb.tb_frame, 'f_back'):
+ sio.write("Capture point (most recent call last):\n")
+ traceback.print_stack(tb.tb_frame.f_back, None, sio)
+
+ traceback.print_exception(typ, val, tb, None, sio)
+ s = sio.getvalue()
+ sio.close()
+ if s[-1:] == "\n":
+ s = s[:-1]
+ return s
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