238 lines
8.8 KiB
Python
238 lines
8.8 KiB
Python
# Copyright 2018 New Vector Ltd
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import functools
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import sys
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from typing import Any, Callable, Generator, List, TypeVar, cast
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from typing_extensions import ParamSpec
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from twisted.internet import defer
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from twisted.internet.defer import Deferred
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from twisted.python.failure import Failure
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# Tracks if we've already patched inlineCallbacks
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_already_patched = False
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T = TypeVar("T")
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P = ParamSpec("P")
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def do_patch() -> None:
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"""
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Patch defer.inlineCallbacks so that it checks the state of the logcontext on exit
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"""
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from synapse.logging.context import current_context
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global _already_patched
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orig_inline_callbacks = defer.inlineCallbacks
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if _already_patched:
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return
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def new_inline_callbacks(
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f: Callable[P, Generator["Deferred[object]", object, T]]
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) -> Callable[P, "Deferred[T]"]:
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@functools.wraps(f)
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def wrapped(*args: P.args, **kwargs: P.kwargs) -> "Deferred[T]":
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start_context = current_context()
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changes: List[str] = []
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orig: Callable[P, "Deferred[T]"] = orig_inline_callbacks(
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_check_yield_points(f, changes)
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)
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try:
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res: "Deferred[T]" = orig(*args, **kwargs)
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except Exception:
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if current_context() != start_context:
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for err in changes:
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print(err, file=sys.stderr)
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err = "%s changed context from %s to %s on exception" % (
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f,
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start_context,
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current_context(),
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)
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print(err, file=sys.stderr)
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raise Exception(err)
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raise
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if not isinstance(res, Deferred) or res.called:
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if current_context() != start_context:
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for err in changes:
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print(err, file=sys.stderr)
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err = "Completed %s changed context from %s to %s" % (
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f,
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start_context,
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current_context(),
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)
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# print the error to stderr because otherwise all we
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# see in travis-ci is the 500 error
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print(err, file=sys.stderr)
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raise Exception(err)
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return res
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if current_context():
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err = (
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"%s returned incomplete deferred in non-sentinel context "
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"%s (start was %s)"
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) % (f, current_context(), start_context)
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print(err, file=sys.stderr)
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raise Exception(err)
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def check_ctx(r: T) -> T:
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if current_context() != start_context:
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for err in changes:
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print(err, file=sys.stderr)
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err = "%s completion of %s changed context from %s to %s" % (
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"Failure" if isinstance(r, Failure) else "Success",
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f,
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start_context,
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current_context(),
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)
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print(err, file=sys.stderr)
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raise Exception(err)
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return r
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res.addBoth(check_ctx)
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return res
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return wrapped
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defer.inlineCallbacks = new_inline_callbacks
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_already_patched = True
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def _check_yield_points(
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f: Callable[P, Generator["Deferred[object]", object, T]],
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changes: List[str],
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) -> Callable:
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"""Wraps a generator that is about to be passed to defer.inlineCallbacks
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checking that after every yield the log contexts are correct.
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It's perfectly valid for log contexts to change within a function, e.g. due
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to new Measure blocks, so such changes are added to the given `changes`
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list instead of triggering an exception.
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Args:
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f: generator function to wrap
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changes: A list of strings detailing how the contexts
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changed within a function.
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Returns:
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function
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"""
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from synapse.logging.context import current_context
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@functools.wraps(f)
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def check_yield_points_inner(
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*args: P.args, **kwargs: P.kwargs
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) -> Generator["Deferred[object]", object, T]:
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gen = f(*args, **kwargs)
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last_yield_line_no = gen.gi_frame.f_lineno
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result: Any = None
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while True:
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expected_context = current_context()
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try:
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isFailure = isinstance(result, Failure)
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if isFailure:
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d = result.throwExceptionIntoGenerator(gen)
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else:
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d = gen.send(result)
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except (StopIteration, defer._DefGen_Return) as e:
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if current_context() != expected_context:
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# This happens when the context is lost sometime *after* the
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# final yield and returning. E.g. we forgot to yield on a
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# function that returns a deferred.
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#
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# We don't raise here as it's perfectly valid for contexts to
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# change in a function, as long as it sets the correct context
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# on resolving (which is checked separately).
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err = (
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"Function %r returned and changed context from %s to %s,"
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" in %s between %d and end of func"
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% (
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f.__qualname__,
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expected_context,
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current_context(),
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f.__code__.co_filename,
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last_yield_line_no,
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)
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)
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changes.append(err)
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# The `StopIteration` or `_DefGen_Return` contains the return value from the
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# generator.
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return cast(T, e.value)
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frame = gen.gi_frame
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if isinstance(d, defer.Deferred) and not d.called:
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# This happens if we yield on a deferred that doesn't follow
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# the log context rules without wrapping in a `make_deferred_yieldable`.
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# We raise here as this should never happen.
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if current_context():
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err = (
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"%s yielded with context %s rather than sentinel,"
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" yielded on line %d in %s"
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% (
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frame.f_code.co_name,
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current_context(),
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frame.f_lineno,
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frame.f_code.co_filename,
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)
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)
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raise Exception(err)
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# the wrapped function yielded a Deferred: yield it back up to the parent
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# inlineCallbacks().
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try:
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result = yield d
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except Exception:
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# this will fish an earlier Failure out of the stack where possible, and
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# thus is preferable to passing in an exception to the Failure
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# constructor, since it results in less stack-mangling.
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result = Failure()
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if current_context() != expected_context:
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# This happens because the context is lost sometime *after* the
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# previous yield and *after* the current yield. E.g. the
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# deferred we waited on didn't follow the rules, or we forgot to
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# yield on a function between the two yield points.
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#
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# We don't raise here as its perfectly valid for contexts to
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# change in a function, as long as it sets the correct context
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# on resolving (which is checked separately).
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err = (
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"%s changed context from %s to %s, happened between lines %d and %d in %s"
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% (
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frame.f_code.co_name,
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expected_context,
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current_context(),
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last_yield_line_no,
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frame.f_lineno,
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frame.f_code.co_filename,
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)
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)
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changes.append(err)
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last_yield_line_no = frame.f_lineno
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return check_yield_points_inner
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