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# 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.
import functools
import sys
from typing import Any, Callable, List
from twisted.internet import defer
from twisted.internet.defer import Deferred
from twisted.python.failure import Failure
# Tracks if we've already patched inlineCallbacks
_already_patched = False
def do_patch() -> None:
"""
Patch defer.inlineCallbacks so that it checks the state of the logcontext on exit
"""
from synapse.logging.context import current_context
global _already_patched
orig_inline_callbacks = defer.inlineCallbacks
if _already_patched:
return
def new_inline_callbacks(f):
@functools.wraps(f)
def wrapped(*args, **kwargs):
start_context = current_context()
changes: List[str] = []
orig = orig_inline_callbacks(_check_yield_points(f, changes))
try:
res = orig(*args, **kwargs)
except Exception:
if 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,
current_context(),
)
print(err, file=sys.stderr)
raise Exception(err)
raise
if not isinstance(res, Deferred) or res.called:
if 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,
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 current_context():
err = (
"%s returned incomplete deferred in non-sentinel context "
"%s (start was %s)"
) % (f, current_context(), start_context)
print(err, file=sys.stderr)
raise Exception(err)
def check_ctx(r):
if 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,
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
_already_patched = True
def _check_yield_points(f: Callable, changes: List[str]) -> Callable:
"""Wraps a generator that is about to be passed to defer.inlineCallbacks
checking that after every yield the log contexts are correct.
It's perfectly valid for log contexts to change within a function, e.g. due
to new Measure blocks, so such changes are added to the given `changes`
list instead of triggering an exception.
Args:
f: generator function to wrap
changes: A list of strings detailing how the contexts
changed within a function.
Returns:
function
"""
from synapse.logging.context import current_context
@functools.wraps(f)
def check_yield_points_inner(*args, **kwargs):
gen = f(*args, **kwargs)
last_yield_line_no = gen.gi_frame.f_lineno
result: Any = None
while True:
expected_context = current_context()
try:
isFailure = isinstance(result, Failure)
if isFailure:
d = result.throwExceptionIntoGenerator(gen)
else:
d = gen.send(result)
except (StopIteration, defer._DefGen_Return) as e:
if 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.
#
# We don't raise here as it's perfectly valid for contexts to
# change in a function, as long as it sets the correct context
# on resolving (which is checked separately).
err = (
"Function %r returned and changed context from %s to %s,"
" in %s between %d and end of func"
% (
f.__qualname__,
expected_context,
current_context(),
f.__code__.co_filename,
last_yield_line_no,
)
)
changes.append(err)
return getattr(e, "value", None)
frame = gen.gi_frame
if isinstance(d, defer.Deferred) and not d.called:
# This happens if we yield on a deferred that doesn't follow
# the log context rules without wrapping in a `make_deferred_yieldable`.
# We raise here as this should never happen.
if current_context():
err = (
"%s yielded with context %s rather than sentinel,"
" yielded on line %d in %s"
% (
frame.f_code.co_name,
current_context(),
frame.f_lineno,
frame.f_code.co_filename,
)
)
raise Exception(err)
# the wrapped function yielded a Deferred: yield it back up to the parent
# inlineCallbacks().
try:
result = yield d
except Exception:
# this will fish an earlier Failure out of the stack where possible, and
# thus is preferable to passing in an exception to the Failure
# constructor, since it results in less stack-mangling.
result = Failure()
if 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.
#
# We don't raise here as its perfectly valid for contexts to
# change in a function, as long as it sets the correct context
# on resolving (which is checked separately).
err = "%s changed context from %s to %s, happened between lines %d and %d in %s" % (
frame.f_code.co_name,
expected_context,
current_context(),
last_yield_line_no,
frame.f_lineno,
frame.f_code.co_filename,
)
changes.append(err)
last_yield_line_no = frame.f_lineno
return check_yield_points_inner
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