# Copyright 2016 Google Inc. All Rights Reserved.
#
# 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.
"""Transport for Python logging handler
Uses a background worker to log to Stackdriver Logging asynchronously.
"""
import atexit
import copy
import threading
from google.cloud.logging.client import Client
from google.cloud.logging.handlers.transports.base import Transport
class _Worker(object):
"""A threaded worker that writes batches of log entries
Writes entries to the logger API.
This class reuses a single :class:`Batch` method to write successive
entries.
Currently, the only public methods are constructing it (which also starts
it) and enqueuing :class:`Logger` (record, message) pairs.
"""
def __init__(self, logger):
self.started = False
self.stopping = False
self.stopped = False
# _entries_condition is used to signal from the main thread whether
# there are any waiting queued logger entries to be written
self._entries_condition = threading.Condition()
# _stop_condition is used to signal from the worker thread to the
# main thread that it's finished its last entries
self._stop_condition = threading.Condition()
# This object continually reuses the same :class:`Batch` object to
# write multiple entries at the same time.
self.logger = logger
self.batch = self.logger.batch()
self._thread = None
# Number in seconds of how long to wait for worker to send remaining
self._stop_timeout = 5
self._start()
def _run(self):
"""The entry point for the worker thread.
Loops until ``stopping`` is set to :data:`True`, and commits batch
entries written during :meth:`enqueue`.
"""
try:
self._entries_condition.acquire()
self.started = True
while not self.stopping:
if len(self.batch.entries) == 0:
# branch coverage of this code extremely flaky
self._entries_condition.wait() # pragma: NO COVER
if len(self.batch.entries) > 0:
self.batch.commit()
finally:
self._entries_condition.release()
# main thread may be waiting for worker thread to finish writing its
# final entries. here we signal that it's done.
self._stop_condition.acquire()
self._stop_condition.notify()
self._stop_condition.release()
def _start(self):
"""Called by this class's constructor
This method is responsible for starting the thread and registering
the exit handlers.
"""
try:
self._entries_condition.acquire()
self._thread = threading.Thread(
target=self._run,
name='google.cloud.logging.handlers.transport.Worker')
self._thread.setDaemon(True)
self._thread.start()
finally:
self._entries_condition.release()
atexit.register(self._stop)
def _stop(self):
"""Signals the worker thread to shut down
Also waits for ``stop_timeout`` seconds for the worker to finish.
This method is called by the ``atexit`` handler registered by
:meth:`start`.
"""
if not self.started or self.stopping:
return
# lock the stop condition first so that the worker
# thread can't notify it's finished before we wait
self._stop_condition.acquire()
# now notify the worker thread to shutdown
self._entries_condition.acquire()
self.stopping = True
self._entries_condition.notify()
self._entries_condition.release()
# now wait for it to signal it's finished
self._stop_condition.wait(self._stop_timeout)
self._stop_condition.release()
self.stopped = True
def enqueue(self, record, message):
"""Queues up a log entry to be written by the background thread."""
try:
self._entries_condition.acquire()
if self.stopping:
return
info = {'message': message, 'python_logger': record.name}
self.batch.log_struct(info, severity=record.levelname)
self._entries_condition.notify()
finally:
self._entries_condition.release()
[docs]class BackgroundThreadTransport(Transport):
"""Aysnchronous transport that uses a background thread.
Writes logging entries as a batch process.
"""
def __init__(self, client, name):
http = copy.deepcopy(client.connection.http)
http = client.connection.credentials.authorize(http)
self.client = Client(client.project,
client.connection.credentials,
http)
logger = self.client.logger(name)
self.worker = _Worker(logger)
[docs] def send(self, record, message):
"""Overrides Transport.send().
:type record: :class:`logging.LogRecord`
:param record: Python log record that the handler was called with.
:type message: str
:param message: The message from the ``LogRecord`` after being
formatted by the associated log formatters.
"""
self.worker.enqueue(record, message)