diff options
Diffstat (limited to 'Doc/howto')
| -rw-r--r-- | Doc/howto/logging-cookbook.rst | 51 | ||||
| -rw-r--r-- | Doc/howto/logging.rst | 63 |
2 files changed, 60 insertions, 54 deletions
diff --git a/Doc/howto/logging-cookbook.rst b/Doc/howto/logging-cookbook.rst index 3e01e4a..1ad3c25 100644 --- a/Doc/howto/logging-cookbook.rst +++ b/Doc/howto/logging-cookbook.rst @@ -97,11 +97,11 @@ The output looks like this:: Multiple handlers and formatters -------------------------------- -Loggers are plain Python objects. The :func:`addHandler` method has no minimum -or maximum quota for the number of handlers you may add. Sometimes it will be -beneficial for an application to log all messages of all severities to a text -file while simultaneously logging errors or above to the console. To set this -up, simply configure the appropriate handlers. The logging calls in the +Loggers are plain Python objects. The :meth:`~Logger.addHandler` method has no +minimum or maximum quota for the number of handlers you may add. Sometimes it +will be beneficial for an application to log all messages of all severities to a +text file while simultaneously logging errors or above to the console. To set +this up, simply configure the appropriate handlers. The logging calls in the application code will remain unchanged. Here is a slight modification to the previous simple module-based configuration example:: @@ -459,8 +459,9 @@ printed on the console; on the server side, you should see something like:: Note that there are some security issues with pickle in some scenarios. If these affect you, you can use an alternative serialization scheme by overriding -the :meth:`makePickle` method and implementing your alternative there, as -well as adapting the above script to use your alternative serialization. +the :meth:`~handlers.SocketHandler.makePickle` method and implementing your +alternative there, as well as adapting the above script to use your alternative +serialization. .. _context-info: @@ -509,9 +510,9 @@ information in the delegated call. Here's a snippet from the code of msg, kwargs = self.process(msg, kwargs) self.logger.debug(msg, *args, **kwargs) -The :meth:`process` method of :class:`LoggerAdapter` is where the contextual -information is added to the logging output. It's passed the message and -keyword arguments of the logging call, and it passes back (potentially) +The :meth:`~LoggerAdapter.process` method of :class:`LoggerAdapter` is where the +contextual information is added to the logging output. It's passed the message +and keyword arguments of the logging call, and it passes back (potentially) modified versions of these to use in the call to the underlying logger. The default implementation of this method leaves the message alone, but inserts an 'extra' key in the keyword argument whose value is the dict-like object @@ -523,8 +524,8 @@ merged into the :class:`LogRecord` instance's __dict__, allowing you to use customized strings with your :class:`Formatter` instances which know about the keys of the dict-like object. If you need a different method, e.g. if you want to prepend or append the contextual information to the message string, -you just need to subclass :class:`LoggerAdapter` and override :meth:`process` -to do what you need. Here is a simple example:: +you just need to subclass :class:`LoggerAdapter` and override +:meth:`~LoggerAdapter.process` to do what you need. Here is a simple example:: class CustomAdapter(logging.LoggerAdapter): """ @@ -633,20 +634,20 @@ threads in a single process *is* supported, logging to a single file from *multiple processes* is *not* supported, because there is no standard way to serialize access to a single file across multiple processes in Python. If you need to log to a single file from multiple processes, one way of doing this is -to have all the processes log to a :class:`SocketHandler`, and have a separate -process which implements a socket server which reads from the socket and logs -to file. (If you prefer, you can dedicate one thread in one of the existing -processes to perform this function.) :ref:`This section <network-logging>` -documents this approach in more detail and includes a working socket receiver -which can be used as a starting point for you to adapt in your own -applications. +to have all the processes log to a :class:`~handlers.SocketHandler`, and have a +separate process which implements a socket server which reads from the socket +and logs to file. (If you prefer, you can dedicate one thread in one of the +existing processes to perform this function.) +:ref:`This section <network-logging>` documents this approach in more detail and +includes a working socket receiver which can be used as a starting point for you +to adapt in your own applications. If you are using a recent version of Python which includes the :mod:`multiprocessing` module, you could write your own handler which uses the -:class:`Lock` class from this module to serialize access to the file from -your processes. The existing :class:`FileHandler` and subclasses do not make -use of :mod:`multiprocessing` at present, though they may do so in the future. -Note that at present, the :mod:`multiprocessing` module does not provide +:class:`~multiprocessing.Lock` class from this module to serialize access to the +file from your processes. The existing :class:`FileHandler` and subclasses do +not make use of :mod:`multiprocessing` at present, though they may do so in the +future. Note that at present, the :mod:`multiprocessing` module does not provide working lock functionality on all platforms (see http://bugs.python.org/issue3770). @@ -878,7 +879,7 @@ Sometimes you want to let a log file grow to a certain size, then open a new file and log to that. You may want to keep a certain number of these files, and when that many files have been created, rotate the files so that the number of files and the size of the files both remain bounded. For this usage pattern, the -logging package provides a :class:`RotatingFileHandler`:: +logging package provides a :class:`~handlers.RotatingFileHandler`:: import glob import logging @@ -1252,7 +1253,7 @@ An example dictionary-based configuration Below is an example of a logging configuration dictionary - it's taken from the `documentation on the Django project <https://docs.djangoproject.com/en/1.3/topics/logging/#configuring-logging>`_. -This dictionary is passed to :func:`~logging.config.dictConfig` to put the configuration into effect:: +This dictionary is passed to :func:`~config.dictConfig` to put the configuration into effect:: LOGGING = { 'version': 1, diff --git a/Doc/howto/logging.rst b/Doc/howto/logging.rst index aa40446..165486a 100644 --- a/Doc/howto/logging.rst +++ b/Doc/howto/logging.rst @@ -469,12 +469,13 @@ Handlers :class:`~logging.Handler` objects are responsible for dispatching the appropriate log messages (based on the log messages' severity) to the handler's -specified destination. Logger objects can add zero or more handler objects to -themselves with an :func:`addHandler` method. As an example scenario, an -application may want to send all log messages to a log file, all log messages -of error or higher to stdout, and all messages of critical to an email address. -This scenario requires three individual handlers where each handler is -responsible for sending messages of a specific severity to a specific location. +specified destination. :class:`Logger` objects can add zero or more handler +objects to themselves with an :meth:`~Logger.addHandler` method. As an example +scenario, an application may want to send all log messages to a log file, all +log messages of error or higher to stdout, and all messages of critical to an +email address. This scenario requires three individual handlers where each +handler is responsible for sending messages of a specific severity to a specific +location. The standard library includes quite a few handler types (see :ref:`useful-handlers`); the tutorials use mainly :class:`StreamHandler` and @@ -485,16 +486,17 @@ themselves with. The only handler methods that seem relevant for application developers who are using the built-in handler objects (that is, not creating custom handlers) are the following configuration methods: -* The :meth:`Handler.setLevel` method, just as in logger objects, specifies the +* The :meth:`~Handler.setLevel` method, just as in logger objects, specifies the lowest severity that will be dispatched to the appropriate destination. Why are there two :func:`setLevel` methods? The level set in the logger determines which severity of messages it will pass to its handlers. The level set in each handler determines which messages that handler will send on. -* :func:`setFormatter` selects a Formatter object for this handler to use. +* :meth:`~Handler.setFormatter` selects a Formatter object for this handler to + use. -* :func:`addFilter` and :func:`removeFilter` respectively configure and - deconfigure filter objects on handlers. +* :meth:`~Handler.addFilter` and :meth:`~Handler.removeFilter` respectively + configure and deconfigure filter objects on handlers. Application code should not directly instantiate and use instances of :class:`Handler`. Instead, the :class:`Handler` class is a base class that @@ -948,16 +950,16 @@ Logged messages are formatted for presentation through instances of the use with the % operator and a dictionary. For formatting multiple messages in a batch, instances of -:class:`BufferingFormatter` can be used. In addition to the format string (which -is applied to each message in the batch), there is provision for header and -trailer format strings. +:class:`~handlers.BufferingFormatter` can be used. In addition to the format +string (which is applied to each message in the batch), there is provision for +header and trailer format strings. When filtering based on logger level and/or handler level is not enough, instances of :class:`Filter` can be added to both :class:`Logger` and -:class:`Handler` instances (through their :meth:`addFilter` method). Before -deciding to process a message further, both loggers and handlers consult all -their filters for permission. If any filter returns a false value, the message -is not processed further. +:class:`Handler` instances (through their :meth:`~Handler.addFilter` method). +Before deciding to process a message further, both loggers and handlers consult +all their filters for permission. If any filter returns a false value, the +message is not processed further. The basic :class:`Filter` functionality allows filtering by specific logger name. If this feature is used, messages sent to the named logger and its @@ -975,12 +977,14 @@ in production. This is so that errors which occur while handling logging events cause the application using logging to terminate prematurely. :class:`SystemExit` and :class:`KeyboardInterrupt` exceptions are never -swallowed. Other exceptions which occur during the :meth:`emit` method of a -:class:`Handler` subclass are passed to its :meth:`handleError` method. +swallowed. Other exceptions which occur during the :meth:`~Handler.emit` method +of a :class:`Handler` subclass are passed to its :meth:`~Handler.handleError` +method. -The default implementation of :meth:`handleError` in :class:`Handler` checks -to see if a module-level variable, :data:`raiseExceptions`, is set. If set, a -traceback is printed to :data:`sys.stderr`. If not set, the exception is swallowed. +The default implementation of :meth:`~Handler.handleError` in :class:`Handler` +checks to see if a module-level variable, :data:`raiseExceptions`, is set. If +set, a traceback is printed to :data:`sys.stderr`. If not set, the exception is +swallowed. .. note:: The default value of :data:`raiseExceptions` is ``True``. This is because during development, you typically want to be notified of any @@ -997,11 +1001,11 @@ Using arbitrary objects as messages In the preceding sections and examples, it has been assumed that the message passed when logging the event is a string. However, this is not the only possibility. You can pass an arbitrary object as a message, and its -:meth:`__str__` method will be called when the logging system needs to convert -it to a string representation. In fact, if you want to, you can avoid +:meth:`~object.__str__` method will be called when the logging system needs to +convert it to a string representation. In fact, if you want to, you can avoid computing a string representation altogether - for example, the -:class:`SocketHandler` emits an event by pickling it and sending it over the -wire. +:class:`~handlers.SocketHandler` emits an event by pickling it and sending it +over the wire. Optimization @@ -1010,9 +1014,10 @@ Optimization Formatting of message arguments is deferred until it cannot be avoided. However, computing the arguments passed to the logging method can also be expensive, and you may want to avoid doing it if the logger will just throw -away your event. To decide what to do, you can call the :meth:`isEnabledFor` -method which takes a level argument and returns true if the event would be -created by the Logger for that level of call. You can write code like this:: +away your event. To decide what to do, you can call the +:meth:`~Logger.isEnabledFor` method which takes a level argument and returns +true if the event would be created by the Logger for that level of call. +You can write code like this:: if logger.isEnabledFor(logging.DEBUG): logger.debug('Message with %s, %s', expensive_func1(), |