summary refs log tree commit diff
path: root/synapse/util/debug.py
diff options
context:
space:
mode:
authorMark Haines <mjark@negativecurvature.net>2015-10-13 18:40:57 +0100
committerMark Haines <mjark@negativecurvature.net>2015-10-13 18:40:57 +0100
commit474274583f664cf3184958bff829d7b50224c9a6 (patch)
tree1185679c0a23bd6f7b25c19ef1b0f873dc1be756 /synapse/util/debug.py
parentMerge pull request #301 from matrix-org/markjh/v2_filtering (diff)
parentEnable stack traces for the demo scripts (diff)
downloadsynapse-474274583f664cf3184958bff829d7b50224c9a6.tar.xz
Merge pull request #303 from matrix-org/markjh/twisted_debugging
Bounce all deferreds through the reactor to make debugging easier.
Diffstat (limited to 'synapse/util/debug.py')
-rw-r--r--synapse/util/debug.py72
1 files changed, 72 insertions, 0 deletions
diff --git a/synapse/util/debug.py b/synapse/util/debug.py
new file mode 100644
index 0000000000..f6a5a841a4
--- /dev/null
+++ b/synapse/util/debug.py
@@ -0,0 +1,72 @@
+# -*- coding: utf-8 -*-
+# Copyright 2015 OpenMarket 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.
+
+from twisted.internet import defer, reactor
+from functools import wraps
+from synapse.util.logcontext import LoggingContext, PreserveLoggingContext
+
+
+def debug_deferreds():
+    """Cause all deferreds to wait for a reactor tick before running their
+    callbacks. This increases the chance of getting a stack trace out of
+    a defer.inlineCallback since the code waiting on the deferred will get
+    a chance to add an errback before the deferred runs."""
+
+    # Helper method for retrieving and restoring the current logging context
+    # around a callback.
+    def with_logging_context(fn):
+        context = LoggingContext.current_context()
+
+        def restore_context_callback(x):
+            with PreserveLoggingContext():
+                LoggingContext.thread_local.current_context = context
+                return fn(x)
+
+        return restore_context_callback
+
+    # We are going to modify the __init__ method of defer.Deferred so we
+    # need to get a copy of the old method so we can still call it.
+    old__init__ = defer.Deferred.__init__
+
+    # We need to create a deferred to bounce the callbacks through the reactor
+    # but we don't want to add a callback when we create that deferred so we
+    # we create a new type of deferred that uses the old __init__ method.
+    # This is safe as long as the old __init__ method doesn't invoke an
+    # __init__ using super.
+    class Bouncer(defer.Deferred):
+        __init__ = old__init__
+
+    # We'll add this as a callback to all Deferreds. Twisted will wait until
+    # the bouncer deferred resolves before calling the callbacks of the
+    # original deferred.
+    def bounce_callback(x):
+        bouncer = Bouncer()
+        reactor.callLater(0, with_logging_context(bouncer.callback), x)
+        return bouncer
+
+    # We'll add this as an errback to all Deferreds. Twisted will wait until
+    # the bouncer deferred resolves before calling the errbacks of the
+    # original deferred.
+    def bounce_errback(x):
+        bouncer = Bouncer()
+        reactor.callLater(0, with_logging_context(bouncer.errback), x)
+        return bouncer
+
+    @wraps(old__init__)
+    def new__init__(self, *args, **kargs):
+        old__init__(self, *args, **kargs)
+        self.addCallbacks(bounce_callback, bounce_errback)
+
+    defer.Deferred.__init__ = new__init__