Move patch_inline_callbacks into synapse/

1 files changed, 179 insertions, 0 deletions

diff --git a/synapse/util/patch_inline_callbacks.py b/synapse/util/patch_inline_callbacks.py
new file mode 100644
index 0000000000..4fb49b0b2b
--- /dev/null
+++ b/synapse/util/patch_inline_callbacks.py
@@ -0,0 +1,179 @@
+# -*- coding: utf-8 -*-
+# Copyright 2018 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.
+
+from __future__ import print_function
+
+import functools
+import sys
+
+from twisted.internet import defer
+from twisted.internet.defer import Deferred
+from twisted.python.failure import Failure
+
+
+def do_patch():
+    """
+    Patch defer.inlineCallbacks so that it checks the state of the logcontext on exit
+    """
+
+    from synapse.logging.context import LoggingContext
+
+    orig_inline_callbacks = defer.inlineCallbacks
+    if hasattr(orig_inline_callbacks, "patched_by_synapse"):
+        return
+
+    def new_inline_callbacks(f):
+        @functools.wraps(f)
+        def wrapped(*args, **kwargs):
+            start_context = LoggingContext.current_context()
+            changes = []
+            orig = orig_inline_callbacks(_check_yield_points(f, changes, start_context))
+
+            try:
+                res = orig(*args, **kwargs)
+            except Exception:
+                if LoggingContext.current_context() != start_context:
+                    for err in changes:
+                        print(err, file=sys.stderr)
+
+                    err = "%s changed context from %s to %s on exception" % (
+                        f,
+                        start_context,
+                        LoggingContext.current_context(),
+                    )
+                    print(err, file=sys.stderr)
+                    raise Exception(err)
+                raise
+
+            if not isinstance(res, Deferred) or res.called:
+                if LoggingContext.current_context() != start_context:
+                    for err in changes:
+                        print(err, file=sys.stderr)
+
+                    err = "Completed %s changed context from %s to %s" % (
+                        f,
+                        start_context,
+                        LoggingContext.current_context(),
+                    )
+                    # print the error to stderr because otherwise all we
+                    # see in travis-ci is the 500 error
+                    print(err, file=sys.stderr)
+                    raise Exception(err)
+                return res
+
+            if LoggingContext.current_context() != LoggingContext.sentinel:
+                err = (
+                    "%s returned incomplete deferred in non-sentinel context "
+                    "%s (start was %s)"
+                ) % (f, LoggingContext.current_context(), start_context)
+                print(err, file=sys.stderr)
+                raise Exception(err)
+
+            def check_ctx(r):
+                if LoggingContext.current_context() != start_context:
+                    for err in changes:
+                        print(err, file=sys.stderr)
+                    err = "%s completion of %s changed context from %s to %s" % (
+                        "Failure" if isinstance(r, Failure) else "Success",
+                        f,
+                        start_context,
+                        LoggingContext.current_context(),
+                    )
+                    print(err, file=sys.stderr)
+                    raise Exception(err)
+                return r
+
+            res.addBoth(check_ctx)
+            return res
+
+        return wrapped
+
+    defer.inlineCallbacks = new_inline_callbacks
+    new_inline_callbacks.patched_by_synapse = True
+
+
+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.
+    """
+
+    from synapse.logging.context import LoggingContext
+
+    @functools.wraps(f)
+    def check_yield_points_inner(*args, **kwargs):
+        expected_context = start_context
+
+        gen = f(*args, **kwargs)
+
+        last_yield_line_no = 1
+        result = None
+        while True:
+            try:
+                isFailure = isinstance(result, Failure)
+                if isFailure:
+                    d = result.throwExceptionIntoGenerator(gen)
+                else:
+                    d = gen.send(result)
+            except (StopIteration, defer._DefGen_Return) as e:
+                if LoggingContext.current_context() != expected_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.
+                    err = (
+                        "Function %r returned and changed context from %s to %s,"
+                        " in %s between %d and end of func"
+                        % (
+                            f.__qualname__,
+                            start_context,
+                            LoggingContext.current_context(),
+                            f.__code__.co_filename,
+                            last_yield_line_no,
+                        )
+                    )
+                    changes.append(err)
+                    # raise Exception(err)
+                return getattr(e, "value", None)
+
+            try:
+                result = yield d
+            except Exception as e:
+                result = Failure(e)
+
+            frame = gen.gi_frame
+
+            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.
+                err = (
+                    "%s changed context from %s to %s, happened between lines %d and %d in %s"
+                    % (
+                        frame.f_code.co_name,
+                        start_context,
+                        LoggingContext.current_context(),
+                        last_yield_line_no,
+                        frame.f_lineno,
+                        frame.f_code.co_filename,
+                    )
+                )
+                changes.append(err)
+                # raise Exception(err)
+
+                expected_context = LoggingContext.current_context()
+
+            last_yield_line_no = frame.f_lineno
+
+    return check_yield_points_inner