MatrixSynapse/synapse/util/__init__.py

# Copyright 2014-2016 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.

import json
import logging
import typing
from typing import Any, Callable, Dict, Generator, Optional

import attr
from frozendict import frozendict
from matrix_common.versionstring import get_distribution_version_string

from twisted.internet import defer, task
from twisted.internet.defer import Deferred
from twisted.internet.interfaces import IDelayedCall, IReactorTime
from twisted.internet.task import LoopingCall
from twisted.python.failure import Failure

from synapse.logging import context

if typing.TYPE_CHECKING:
    pass

logger = logging.getLogger(__name__)


def _reject_invalid_json(val: Any) -> None:
    """Do not allow Infinity, -Infinity, or NaN values in JSON."""
    raise ValueError("Invalid JSON value: '%s'" % val)


def _handle_frozendict(obj: Any) -> Dict[Any, Any]:
    """Helper for json_encoder. Makes frozendicts serializable by returning
    the underlying dict
    """
    if type(obj) is frozendict:
        # fishing the protected dict out of the object is a bit nasty,
        # but we don't really want the overhead of copying the dict.
        try:
            # Safety: we catch the AttributeError immediately below.
            # See https://github.com/matrix-org/python-canonicaljson/issues/36#issuecomment-927816293
            # for discussion on how frozendict's internals have changed over time.
            return obj._dict  # type: ignore[attr-defined]
        except AttributeError:
            # When the C implementation of frozendict is used,
            # there isn't a `_dict` attribute with a dict
            # so we resort to making a copy of the frozendict
            return dict(obj)
    raise TypeError(
        "Object of type %s is not JSON serializable" % obj.__class__.__name__
    )


# A custom JSON encoder which:
#   * handles frozendicts
#   * produces valid JSON (no NaNs etc)
#   * reduces redundant whitespace
json_encoder = json.JSONEncoder(
    allow_nan=False, separators=(",", ":"), default=_handle_frozendict
)

# Create a custom decoder to reject Python extensions to JSON.
json_decoder = json.JSONDecoder(parse_constant=_reject_invalid_json)


def unwrapFirstError(failure: Failure) -> Failure:
    # Deprecated: you probably just want to catch defer.FirstError and reraise
    # the subFailure's value, which will do a better job of preserving stacktraces.
    # (actually, you probably want to use yieldable_gather_results anyway)
    failure.trap(defer.FirstError)
    return failure.value.subFailure  # type: ignore[union-attr]  # Issue in Twisted's annotations


@attr.s(slots=True)
class Clock:
    """
    A Clock wraps a Twisted reactor and provides utilities on top of it.

    Args:
        reactor: The Twisted reactor to use.
    """

    _reactor: IReactorTime = attr.ib()

    @defer.inlineCallbacks  # type: ignore[arg-type]  # Issue in Twisted's type annotations
    def sleep(self, seconds: float) -> "Generator[Deferred[float], Any, Any]":
        d: defer.Deferred[float] = defer.Deferred()
        with context.PreserveLoggingContext():
            self._reactor.callLater(seconds, d.callback, seconds)
            res = yield d
        return res

    def time(self) -> float:
        """Returns the current system time in seconds since epoch."""
        return self._reactor.seconds()

    def time_msec(self) -> int:
        """Returns the current system time in milliseconds since epoch."""
        return int(self.time() * 1000)

    def looping_call(
        self, f: Callable, msec: float, *args: Any, **kwargs: Any
    ) -> LoopingCall:
        """Call a function repeatedly.

        Waits `msec` initially before calling `f` for the first time.

        Note that the function will be called with no logcontext, so if it is anything
        other than trivial, you probably want to wrap it in run_as_background_process.

        Args:
            f: The function to call repeatedly.
            msec: How long to wait between calls in milliseconds.
            *args: Postional arguments to pass to function.
            **kwargs: Key arguments to pass to function.
        """
        call = task.LoopingCall(f, *args, **kwargs)
        call.clock = self._reactor
        d = call.start(msec / 1000.0, now=False)
        d.addErrback(log_failure, "Looping call died", consumeErrors=False)
        return call

    def call_later(
        self, delay: float, callback: Callable, *args: Any, **kwargs: Any
    ) -> IDelayedCall:
        """Call something later

        Note that the function will be called with no logcontext, so if it is anything
        other than trivial, you probably want to wrap it in run_as_background_process.

        Args:
            delay: How long to wait in seconds.
            callback: Function to call
            *args: Postional arguments to pass to function.
            **kwargs: Key arguments to pass to function.
        """

        def wrapped_callback(*args: Any, **kwargs: Any) -> None:
            with context.PreserveLoggingContext():
                callback(*args, **kwargs)

        with context.PreserveLoggingContext():
            return self._reactor.callLater(delay, wrapped_callback, *args, **kwargs)

    def cancel_call_later(self, timer: IDelayedCall, ignore_errs: bool = False) -> None:
        try:
            timer.cancel()
        except Exception:
            if not ignore_errs:
                raise


def log_failure(
    failure: Failure, msg: str, consumeErrors: bool = True
) -> Optional[Failure]:
    """Creates a function suitable for passing to `Deferred.addErrback` that
    logs any failures that occur.

    Args:
        failure: The Failure to log
        msg: Message to log
        consumeErrors: If true consumes the failure, otherwise passes on down
            the callback chain

    Returns:
        The Failure if consumeErrors is false. None, otherwise.
    """

    logger.error(
        msg, exc_info=(failure.type, failure.value, failure.getTracebackObject())  # type: ignore[arg-type]
    )

    if not consumeErrors:
        return failure
    return None


# Version string with git info. Computed here once so that we don't invoke git multiple
# times.
SYNAPSE_VERSION = get_distribution_version_string("matrix-synapse", __file__)