diff options
Diffstat (limited to 'logutils/queue.py')
| -rw-r--r-- | logutils/queue.py | 213 |
1 files changed, 213 insertions, 0 deletions
diff --git a/logutils/queue.py b/logutils/queue.py new file mode 100644 index 0000000..6b30bd5 --- /dev/null +++ b/logutils/queue.py @@ -0,0 +1,213 @@ +# Copyright (C) 2010 Vinay Sajip. All Rights Reserved. +# +# Permission to use, copy, modify, and distribute this software and its +# documentation for any purpose and without fee is hereby granted, +# provided that the above copyright notice appear in all copies and that +# both that copyright notice and this permission notice appear in +# supporting documentation, and that the name of Vinay Sajip +# not be used in advertising or publicity pertaining to distribution +# of the software without specific, written prior permission. +# VINAY SAJIP DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING +# ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL +# VINAY SAJIP BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR +# ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER +# IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT +# OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. +# + +import logging +try: + import Queue as queue +except ImportError: + import queue +import threading + +class QueueHandler(logging.Handler): + """ + This handler sends events to a queue. Typically, it would be used together + with a multiprocessing Queue to centralise logging to file in one process + (in a multi-process application), so as to avoid file write contention + between processes. + + This code is new in Python 3.2, but this class can be copy pasted into + user code for use with earlier Python versions. + """ + + def __init__(self, queue): + """ + Initialise an instance, using the passed queue. + """ + logging.Handler.__init__(self) + self.queue = queue + + def enqueue(self, record): + """ + Enqueue a record. + + The base implementation uses put_nowait. You may want to override + this method if you want to use blocking, timeouts or custom queue + implementations. + """ + self.queue.put_nowait(record) + + def prepare(self, record): + """ + Prepares a record for queuing. The object returned by this method is + enqueued. + + The base implementation formats the record to merge the message + and arguments, and removes unpickleable items from the record + in-place. + + You might want to override this method if you want to convert + the record to a dict or JSON string, or send a modified copy + of the record while leaving the original intact. + """ + # The format operation gets traceback text into record.exc_text + # (if there's exception data), and also puts the message into + # record.message. We can then use this to replace the original + # msg + args, as these might be unpickleable. We also zap the + # exc_info attribute, as it's no longer needed and, if not None, + # will typically not be pickleable. + self.format(record) + record.msg = record.message + record.args = None + record.exc_info = None + return record + + def emit(self, record): + """ + Emit a record. + + Writes the LogRecord to the queue, preparing it for pickling first. + """ + try: + self.enqueue(self.prepare(record)) + except (KeyboardInterrupt, SystemExit): + raise + except: + self.handleError(record) + +class QueueListener(object): + """ + This class implements an internal threaded listener which watches for + LogRecords being added to a queue, removes them and passes them to a + list of handlers for processing. + """ + _sentinel = None + + def __init__(self, queue, *handlers): + """ + Initialise an instance with the specified queue and + handlers. + """ + self.queue = queue + self.handlers = handlers + self._stop = threading.Event() + self._thread = None + + def dequeue(self, block): + """ + Dequeue a record and return it, optionally blocking. + + The base implementation uses get. You may want to override this method + if you want to use timeouts or work with custom queue implementations. + """ + return self.queue.get(block) + + def start(self): + """ + Start the listener. + + This starts up a background thread to monitor the queue for + LogRecords to process. + """ + self._thread = t = threading.Thread(target=self._monitor) + t.setDaemon(True) + t.start() + + def prepare(self , record): + """ + Prepare a record for handling. + + This method just returns the passed-in record. You may want to + override this method if you need to do any custom marshalling or + manipulation of the record before passing it to the handlers. + """ + return record + + def handle(self, record): + """ + Handle a record. + + This just loops through the handlers offering them the record + to handle. + """ + record = self.prepare(record) + for handler in self.handlers: + handler.handle(record) + + def _monitor(self): + """ + Monitor the queue for records, and ask the handler + to deal with them. + + This method runs on a separate, internal thread. + The thread will terminate if it sees a sentinel object in the queue. + """ + q = self.queue + has_task_done = hasattr(q, 'task_done') + while not self._stop.isSet(): + try: + record = self.dequeue(True) + if record is self._sentinel: + break + self.handle(record) + if has_task_done: + q.task_done() + except queue.Empty: + pass + # There might still be records in the queue. + while True: + try: + record = self.dequeue(False) + if record is self._sentinel: + break + self.handle(record) + if has_task_done: + q.task_done() + except queue.Empty: + break + + def stop(self): + """ + Stop the listener. + + This asks the thread to terminate, and then waits for it to do so. + Note that if you don't call this before your application exits, there + may be some records still left on the queue, which won't be processed. + """ + self._stop.set() + self.queue.put_nowait(self._sentinel) + self._thread.join() + self._thread = None + +class NullHandler(logging.Handler): + """ + This handler does nothing. It's intended to be used to avoid the + "No handlers could be found for logger XXX" one-off warning. This is + important for library code, which may contain code to log events. If a user + of the library does not configure logging, the one-off warning might be + produced; to avoid this, the library developer simply needs to instantiate + a NullHandler and add it to the top-level logger of the library module or + package. + """ + def handle(self, record): + pass + + def emit(self, record): + pass + + def createLock(self): + self.lock = None + |