diff options
Diffstat (limited to 'Doc/howto')
| -rw-r--r-- | Doc/howto/logging-cookbook.rst | 140 |
1 files changed, 126 insertions, 14 deletions
diff --git a/Doc/howto/logging-cookbook.rst b/Doc/howto/logging-cookbook.rst index ad3e34d..d8ebeab 100644 --- a/Doc/howto/logging-cookbook.rst +++ b/Doc/howto/logging-cookbook.rst @@ -1846,8 +1846,11 @@ the use of a :class:`Filter` does not provide the desired result. .. _zeromq-handlers: -Subclassing QueueHandler - a ZeroMQ example -------------------------------------------- +Subclassing QueueHandler and QueueListener- a ZeroMQ example +------------------------------------------------------------ + +Subclass ``QueueHandler`` +^^^^^^^^^^^^^^^^^^^^^^^^^ You can use a :class:`QueueHandler` subclass to send messages to other kinds of queues, for example a ZeroMQ 'publish' socket. In the example below,the @@ -1885,8 +1888,8 @@ data needed by the handler to create the socket:: self.queue.close() -Subclassing QueueListener - a ZeroMQ example --------------------------------------------- +Subclass ``QueueListener`` +^^^^^^^^^^^^^^^^^^^^^^^^^^ You can also subclass :class:`QueueListener` to get messages from other kinds of queues, for example a ZeroMQ 'subscribe' socket. Here's an example:: @@ -1903,25 +1906,134 @@ of queues, for example a ZeroMQ 'subscribe' socket. Here's an example:: msg = self.queue.recv_json() return logging.makeLogRecord(msg) +.. _pynng-handlers: -.. seealso:: +Subclassing QueueHandler and QueueListener- a ``pynng`` example +--------------------------------------------------------------- - Module :mod:`logging` - API reference for the logging module. +In a similar way to the above section, we can implement a listener and handler +using `pynng <https://pypi.org/project/pynng/>`_, which is a Python binding to +`NNG <https://nng.nanomsg.org/>`_, billed as a spiritual successor to ZeroMQ. +The following snippets illustrate -- you can test them in an environment which has +``pynng`` installed. Juat for variety, we present the listener first. - Module :mod:`logging.config` - Configuration API for the logging module. - Module :mod:`logging.handlers` - Useful handlers included with the logging module. +Subclass ``QueueListener`` +^^^^^^^^^^^^^^^^^^^^^^^^^^ + +.. code-block:: python + + import json + import logging + import logging.handlers + + import pynng - :ref:`A basic logging tutorial <logging-basic-tutorial>` + DEFAULT_ADDR = "tcp://localhost:13232" - :ref:`A more advanced logging tutorial <logging-advanced-tutorial>` + interrupted = False + class NNGSocketListener(logging.handlers.QueueListener): + + def __init__(self, uri, /, *handlers, **kwargs): + # Have a timeout for interruptability, and open a + # subscriber socket + socket = pynng.Sub0(listen=uri, recv_timeout=500) + # The b'' subscription matches all topics + topics = kwargs.pop('topics', None) or b'' + socket.subscribe(topics) + # We treat the socket as a queue + super().__init__(socket, *handlers, **kwargs) + + def dequeue(self, block): + data = None + # Keep looping while not interrupted and no data received over the + # socket + while not interrupted: + try: + data = self.queue.recv(block=block) + break + except pynng.Timeout: + pass + except pynng.Closed: # sometimes hit when you hit Ctrl-C + break + if data is None: + return None + # Get the logging event sent from a publisher + event = json.loads(data.decode('utf-8')) + return logging.makeLogRecord(event) + + def enqueue_sentinel(self): + # Not used in this implementation, as the socket isn't really a + # queue + pass + + logging.getLogger('pynng').propagate = False + listener = NNGSocketListener(DEFAULT_ADDR, logging.StreamHandler(), topics=b'') + listener.start() + print('Press Ctrl-C to stop.') + try: + while True: + pass + except KeyboardInterrupt: + interrupted = True + finally: + listener.stop() + + +Subclass ``QueueHandler`` +^^^^^^^^^^^^^^^^^^^^^^^^^ .. currentmodule:: logging +.. code-block:: python + + import json + import logging + import logging.handlers + import time + import random + + import pynng + + DEFAULT_ADDR = "tcp://localhost:13232" + + class NNGSocketHandler(logging.handlers.QueueHandler): + + def __init__(self, uri): + socket = pynng.Pub0(dial=uri, send_timeout=500) + super().__init__(socket) + + def enqueue(self, record): + # Send the record as UTF-8 encoded JSON + d = dict(record.__dict__) + data = json.dumps(d) + self.queue.send(data.encode('utf-8')) + + def close(self): + self.queue.close() + + logging.getLogger('pynng').propagate = False + handler = NNGSocketHandler(DEFAULT_ADDR) + logging.basicConfig(level=logging.DEBUG, + handlers=[logging.StreamHandler(), handler], + format='%(levelname)-8s %(name)10s %(message)s') + levels = (logging.DEBUG, logging.INFO, logging.WARNING, logging.ERROR, + logging.CRITICAL) + logger_names = ('myapp', 'myapp.lib1', 'myapp.lib2') + msgno = 1 + while True: + # Just randomly select some loggers and levels and log away + level = random.choice(levels) + logger = logging.getLogger(random.choice(logger_names)) + logger.log(level, 'Message no. %5d' % msgno) + msgno += 1 + delay = random.random() * 2 + 0.5 + time.sleep(delay) + +You can run the above two snippets in separate command shells. + + An example dictionary-based configuration ----------------------------------------- @@ -3418,7 +3530,7 @@ The worker thread is implemented using Qt's ``QThread`` class rather than the :mod:`threading` module, as there are circumstances where one has to use ``QThread``, which offers better integration with other ``Qt`` components. -The code should work with recent releases of either ``PySide6``, ``PyQt6``, +The code should work with recent releases of any of ``PySide6``, ``PyQt6``, ``PySide2`` or ``PyQt5``. You should be able to adapt the approach to earlier versions of Qt. Please refer to the comments in the code snippet for more detailed information. |