synapse-product/synapse/logging/_remote.py

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# Copyright 2020 The Matrix.org Foundation C.I.C.
#
# 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 logging
import sys
import traceback
from collections import deque
from ipaddress import IPv4Address, IPv6Address, ip_address
from math import floor
from typing import Callable, Optional
import attr
from typing_extensions import Deque
from zope.interface import implementer
from twisted.application.internet import ClientService
from twisted.internet.defer import CancelledError, Deferred
from twisted.internet.endpoints import (
HostnameEndpoint,
TCP4ClientEndpoint,
TCP6ClientEndpoint,
)
from twisted.internet.interfaces import IPushProducer, IStreamClientEndpoint
from twisted.internet.protocol import Factory, Protocol
from twisted.internet.tcp import Connection
from twisted.python.failure import Failure
logger = logging.getLogger(__name__)
@attr.s
@implementer(IPushProducer)
class LogProducer:
"""
An IPushProducer that writes logs from its buffer to its transport when it
is resumed.
Args:
buffer: Log buffer to read logs from.
transport: Transport to write to.
format: A callable to format the log record to a string.
"""
# This is essentially ITCPTransport, but that is missing certain fields
# (connected and registerProducer) which are part of the implementation.
transport = attr.ib(type=Connection)
_format = attr.ib(type=Callable[[logging.LogRecord], str])
_buffer = attr.ib(type=deque)
_paused = attr.ib(default=False, type=bool, init=False)
def pauseProducing(self):
self._paused = True
def stopProducing(self):
self._paused = True
self._buffer = deque()
def resumeProducing(self):
# If we're already producing, nothing to do.
self._paused = False
# Loop until paused.
while self._paused is False and (self._buffer and self.transport.connected):
try:
# Request the next record and format it.
record = self._buffer.popleft()
msg = self._format(record)
# Send it as a new line over the transport.
self.transport.write(msg.encode("utf8"))
self.transport.write(b"\n")
except Exception:
# Something has gone wrong writing to the transport -- log it
# and break out of the while.
traceback.print_exc(file=sys.__stderr__)
break
class RemoteHandler(logging.Handler):
"""
An logging handler that writes logs to a TCP target.
Args:
host: The host of the logging target.
port: The logging target's port.
maximum_buffer: The maximum buffer size.
"""
def __init__(
self,
host: str,
port: int,
maximum_buffer: int = 1000,
level=logging.NOTSET,
_reactor=None,
):
super().__init__(level=level)
self.host = host
self.port = port
self.maximum_buffer = maximum_buffer
self._buffer: Deque[logging.LogRecord] = deque()
self._connection_waiter: Optional[Deferred] = None
self._producer: Optional[LogProducer] = None
# Connect without DNS lookups if it's a direct IP.
if _reactor is None:
from twisted.internet import reactor
_reactor = reactor
try:
ip = ip_address(self.host)
if isinstance(ip, IPv4Address):
endpoint: IStreamClientEndpoint = TCP4ClientEndpoint(
_reactor, self.host, self.port
)
elif isinstance(ip, IPv6Address):
endpoint = TCP6ClientEndpoint(_reactor, self.host, self.port)
else:
raise ValueError("Unknown IP address provided: %s" % (self.host,))
except ValueError:
endpoint = HostnameEndpoint(_reactor, self.host, self.port)
factory = Factory.forProtocol(Protocol)
self._service = ClientService(endpoint, factory, clock=_reactor)
self._service.startService()
self._stopping = False
self._connect()
def close(self):
self._stopping = True
self._service.stopService()
def _connect(self) -> None:
"""
Triggers an attempt to connect then write to the remote if not already writing.
"""
# Do not attempt to open multiple connections.
if self._connection_waiter:
return
def fail(failure: Failure) -> None:
# If the Deferred was cancelled (e.g. during shutdown) do not try to
# reconnect (this will cause an infinite loop of errors).
if failure.check(CancelledError) and self._stopping:
return
# For a different error, print the traceback and re-connect.
failure.printTraceback(file=sys.__stderr__)
self._connection_waiter = None
self._connect()
def writer(result: Protocol) -> None:
# Force recognising transport as a Connection and not the more
# generic ITransport.
transport: Connection = result.transport # type: ignore
# We have a connection. If we already have a producer, and its
# transport is the same, just trigger a resumeProducing.
if self._producer and transport is self._producer.transport:
self._producer.resumeProducing()
self._connection_waiter = None
return
# If the producer is still producing, stop it.
if self._producer:
self._producer.stopProducing()
# Make a new producer and start it.
self._producer = LogProducer(
buffer=self._buffer,
transport=transport,
format=self.format,
)
transport.registerProducer(self._producer, True)
self._producer.resumeProducing()
self._connection_waiter = None
deferred: Deferred = self._service.whenConnected(failAfterFailures=1)
deferred.addCallbacks(writer, fail)
self._connection_waiter = deferred
def _handle_pressure(self) -> None:
"""
Handle backpressure by shedding records.
The buffer will, in this order, until the buffer is below the maximum:
- Shed DEBUG records.
- Shed INFO records.
- Shed the middle 50% of the records.
"""
if len(self._buffer) <= self.maximum_buffer:
return
# Strip out DEBUGs
self._buffer = deque(
filter(lambda record: record.levelno > logging.DEBUG, self._buffer)
)
if len(self._buffer) <= self.maximum_buffer:
return
# Strip out INFOs
self._buffer = deque(
filter(lambda record: record.levelno > logging.INFO, self._buffer)
)
if len(self._buffer) <= self.maximum_buffer:
return
# Cut the middle entries out
buffer_split = floor(self.maximum_buffer / 2)
old_buffer = self._buffer
self._buffer = deque()
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for _ in range(buffer_split):
self._buffer.append(old_buffer.popleft())
end_buffer = []
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for _ in range(buffer_split):
end_buffer.append(old_buffer.pop())
self._buffer.extend(reversed(end_buffer))
def emit(self, record: logging.LogRecord) -> None:
self._buffer.append(record)
# Handle backpressure, if it exists.
try:
self._handle_pressure()
except Exception:
# If handling backpressure fails, clear the buffer and log the
# exception.
self._buffer.clear()
logger.warning("Failed clearing backpressure")
# Try and write immediately.
self._connect()