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# Authors: John Dennis <jdennis@redhat.com> # # Copyright (C) 2011 Red Hat # see file 'COPYING' for use and warranty information # # This program is free software; you can redistribute it and/or modify # it under the terms of the GNU General Public License as published by # the Free Software Foundation, either version 3 of the License, or # (at your option) any later version. # # This program is distributed in the hope that it will be useful, # but WITHOUT ANY WARRANTY; without even the implied warranty of # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the # GNU General Public License for more details. # # You should have received a copy of the GNU General Public License # along with this program. If not, see <http://www.gnu.org/licenses/>.
Quick Start Guide For Using This Module =======================================
This module implements a Log Manager class which wraps the Python logging module and provides some utility functions for use with logging. All logging operations should be done through the `LogManager` where available. *DO NOT create objects using the Python logging module, the log manager will be unaware of them.*
This module was designed for ease of use while preserving advanced functionality and performance. You must perform the following steps.
1. Import the log_manger module and instantiate *one* `LogManager` instance for your application or library. The `LogManager` is configured via `LogManager.configure()` whose values are easily populated from command line options or a config file. You can modify the configuration again at any point.
2. Create one or more output handlers via `LogManager.create_log_handlers()` an easy to use yet powerful interface.
3. In your code create loggers via `LogManager.get_logger()`. Since loggers are normally bound to a class this method is optimized for that case, all you need to do in the call ``__init__()`` is::
log_mgr.get_logger(self, True)
Then emitting messages is as simple as ``self.debug()`` or ``self.error()``
Example: --------
::
# Step 1, Create log manager and configure it prog_name = 'my_app' log_mgr = LogManager(prog_name) log_mgr.configure(dict(verbose=True))
# Step 2, Create handlers log_mgr.create_log_handlers([dict(name='my_app stdout', stream=sys.stdout, level=logging.INFO), dict(name='my_app file', filename='my_app.log', level=logging.DEBUG)])
# Step 3, Create and use a logger in your code class FooBar: def __init__(self, name): log_mgr.get_logger(self, True) self.info("I'm alive! %s", name)
foobar = FooBar('Dr. Frankenstein')
# Dump the log manager state for illustration print log_mgr
Running the above code would produce::
<INFO>: I'm alive! Dr. Frankenstein
root_logger_name: my_app configure_state: None default_level: INFO debug: False verbose: True number of loggers: 2 "my_app" [level=INFO] "my_app.__main__.FooBar" [level=INFO] number of handlers: 2 "my_app file" [level=DEBUG] "my_app stdout" [level=INFO] number of logger regexps: 0
*Note, Steps 1 & 2 were broken out for expository purposes.* You can pass your handler configuration into `LogManager.configure()`. The above could have been simpler and more compact.::
# Step 1 & 2, Create log manager, and configure it and handlers prog_name = 'my_app' log_mgr = LogManager(prog_name) log_mgr.configure(dict(verbose=True, handlers = [dict(name='my_app stdout', stream=sys.stdout, level=logging.INFO), dict(name='my_app file', filename='my_app.log', level=logging.DEBUG)])
FAQ (Frequently Asked Questions) ================================
#. **Why is this better than logging.basicConfig? The short example for the LogManager doesn't seem much different in complexity from basicConfig?**
* You get independent logging namespaces. You can instantiate multiple logging namespaces. If you use this module you'll be isolated from other users of the Python logging module avoiding conflicts.
* Creating and initializing loggers for classes is trivial. One simple call creates the logger, configures it, and sets logging methods on the class instance.
* You can easily configure individual loggers to different levels. For example turn on debuging for just the part of the code you're working on.
* The configuration is both simple and powerful. You get many more options than with basicConfig.
* You can dynamically reset the logging configuration during execution, you're not forced to live with the config established during program initialization.
* The manager optimizes the use of the logging objects, you'll spend less time executing pointless logging code for messages that won't be emitted.
* You can see the state of all the logging objects in your namespace from one centrally managed location.
* You can configure a LogManager to use the standard logging root logger and get all the benefits of this API.
#. **How do I turn on debug logging for a specific class without affecting the rest of the logging configuration?**
Use a logger regular expression to bind a custom level to loggers whose name matches the regexp. See `LogManager.configure()` for details.
Lets say you want to set your Foo.Bar class to debug, then do this::
log_mgr.configure(dict(logger_regexps=[(r'Foo\.Bar', 'debug')]))
#. **I set the default_level but all my loggers are configured with a higher level, what happened?**
You probably don't have any handlers defined at or below the default_level. The level set on a logger will never be lower than the lowest level handler available to that logger.
#. **My logger's all have their level set to a huge integer, why?**
See above. Logger's will never have a level less than the level of the handlers visible to the logger. If there are no handlers then loggers can't output anything so their level is set to maxint.
#. **I set the default_level but all the loggers are configured at INFO or DEBUG, what happened?**
The verbose and debug config flags set the default_level to INFO and DEBUG respectively as a convenience.
#. **I'm not seeing messages output when I expect them to be, what's wrong?**
For a message to be emitted the following 3 conditions must hold:
* Message level >= logger's level * Message level >= handler's level * The message was not elided by a filter
To verify the above conditions hold print out the log manager state (e.g. print log_mgr). Locate your logger, what level is at? Locate the handler you expected to see the message appear on, what level is it?
A General Discussion of Python Logging ======================================
The design of this module is driven by how the Python logging module works. The following discussion complements the Python Logging Howto, fills in some missing information and covers strategies for implementing different functionality along with the trade-offs involved.
Understanding when & how log messages are emitted: --------------------------------------------------
Loggers provide the application interface for logging. Every logger object has the following methods debug(), info(), warning(), error(), critical(), exception() and log() all of which can accept a format string and arguments. Applications generate logging messages by calling one of these methods to produce a formatted message.
A logger's effective level is the first explicitly set level found when searching from the logger through it's ancestors terminating at the root logger. The root logger always has an explicit level (defaults to WARNING).
For a message to be emitted by a handler the following must be true:
The logger's effective level must >= message level and it must not be filtered by a filter attached to the logger, otherwise the message is discarded.
If the message survives the logger check it is passed to a list of handlers. A handler will emit the message if the handler's level >= message level and its not filtered by a filter attached to the handler.
The list of handlers is determined thusly: Each logger has a list of handlers (which may be empty). Starting with the logger the message was bound to the message is passed to each of it's handlers. Then the process repeats itself by traversing the chain of loggers through all of it's ancestors until it reaches the root logger. The logger traversal will be terminated if the propagate flag on a logger is False (by default propagate is True).
Let's look at a hypothetical logger hierarchy (tree)::
A / \\ B D / C
There are 4 loggers and 3 handlers
Loggers:
+-------+---------+---------+-----------+----------+ |Logger | Level | Filters | Propagate | Handlers | +=======+=========+=========+===========+==========+ | A | WARNING | [] | False | [h1,h2] | +-------+---------+---------+-----------+----------+ | A.B | ERROR | [] | False | [h3] | +-------+---------+---------+-----------+----------+ | A.B.C | DEBUG | [] | True | | +-------+---------+---------+-----------+----------+ | A.D | | [] | True | | +-------+---------+---------+-----------+----------+
Handlers:
+---------+---------+---------+ | Handler | Level | Filters | +=========+=========+=========+ | h1 | ERROR | [] | +---------+---------+---------+ | h2 | WARNING | [] | +---------+---------+---------+ | h3 | DEBUG | [] | +---------+---------+---------+
Each of the loggers and handlers have empty filter lists in this example thus the filter checks will always pass.
If a debug message is posted logger A.B.C the following would happen. The effective level is determined. Since it does not have a level set it's parent (A.B) is examined which has ERROR set, therefore the effective level of A.B.C is ERROR. Processing immediately stops because the logger's level of ERROR does not permit debug messages.
If an error message is posted on logger A.B.C it passes the logger level check and filter check therefore the message is passed along to the handlers. The list of handlers on A.B.C is empty so no handlers are called at this position in the logging hierarchy. Logger A.B.C's propagate flag is True so parent logger A.B handlers are invoked. Handler h3's level is DEBUG, it passes both the level and filter check thus h3 emits the message. Processing now stops because logger A.B's propagate flag is False.
Now let's see what would happen if a warning message was posted on logger A.D. It's effective level is WARNING because logger A.D does not have a level set, it's only ancestor is logger A, the root logger which has a level of WARNING, thus logger's A.D effective level is WARNING. Logger A.D has no handlers, it's propagate flag is True so the message is passed to it's parent logger A, the root logger. Logger A has two handlers h1 and h2. The level of h1 is ERROR so the warning message is discarded by h1, nothing is emitted by h1. Next handler h2 is invoked, it's level is WARNING so it passes both the level check and the filter check, thus h2 emits the warning message.
How to configure independent logging spaces: --------------------------------------------
A common idiom is to hang all handlers off the root logger and set the root loggers level to the desired verbosity. But this simplistic approach runs afoul of several problems, in particular who controls logging (accomplished by configuring the root logger). The usual advice is to check and see if the root logger has any handlers set, if so someone before you has configured logging and you should inherit their configuration, all you do is add your own loggers without any explicitly set level. If the root logger doesn't have handlers set then you go ahead and configure the root logger to your preference. The idea here is if your code is being loaded by another application you want to defer to that applications logging configuration but if your code is running stand-alone you need to set up logging yourself.
But sometimes your code really wants it's own logging configuration managed only by yourself completely independent of any logging configuration by someone who may have loaded your code. Even if you code is not designed to be loaded as a package or module you may be faced with this problem. A trivial example of this is running your code under a unit test framework which itself uses the logging facility (remember there is only ever one root logger in any Python process).
Fortunately there is a simple way to accommodate this. All you need to do is create a "fake" root in the logging hierarchy which belongs to you. You set your fake root's propagate flag to False, set a level on it and you'll hang your handlers off this fake root. Then when you create your loggers each should be a descendant of this fake root. Now you've completely isolated yourself in the logging hierarchy and won't be influenced by any other logging configuration. As an example let's say your your code is called 'foo' and so you name your fake root logger 'foo'.::
my_root = logging.getLogger('foo') # child of the root logger my_root.propagate = False my_root.setLevel(logging.DEBUG) my_root.addHandler(my_handler)
Then every logger you create should have 'foo.' prepended to it's name. If you're logging my module your module's logger would be created like this::
module_logger = logging.getLogger('foo.%s' % __module__)
If you're logging by class then your class logger would be::
class_logger = logging.getLogger('foo.%s.%s' % (self.__module__, self.__class__.__name__))
How to set levels: ------------------
An instinctive or simplistic assumption is to set the root logger to a high logging level, for example ERROR. After all you don't want to be spamming users with debug and info messages. Let's also assume you've got two handlers, one for a file and one for the console, both attached to the root logger (a common configuration) and you haven't set the level on either handler (in which case the handler will emit all levels).
But now let's say you want to turn on debugging, but just to the file, the console should continue to only emit error messages.
You set the root logger's level to DEBUG. The first thing you notice is that you're getting debug message both in the file and on the console because the console's handler does not have a level set. Not what you want.
So you go back restore the root loggers level back to it's original ERROR level and set the file handler's level to DEBUG and the console handler's level to ERROR. Now you don't get any debug messages because the root logger is blocking all messages below the level of ERROR and doesn't invoke any handlers. The file handler attached to the root logger even though it's level is set to DEBUG never gets a chance to process the message.
*IMPORTANT:* You have to set the logger's level to the minimum of all the attached handler's levels, otherwise the logger may block the message from ever reaching any handler.
In this example the root logger's level must be set to DEBUG, the file handler's level to DEBUG, and the console handler's level set to ERROR.
Now let's take a more real world example which is a bit more complicated. It's typical to assign loggers to every major class. In fact this is the design strategy of Java logging from which the Python logging is modeled. In a large complex application or library that means dozens or possibly hundreds of loggers. Now lets say you need to trace what is happening with one class. If you use the simplistic configuration outlined above you'll set the log level of the root logger and one of the handlers to debug. Now you're flooded with debug message from every logger in the system when all you wanted was the debug messages from just one class.
How can you get fine grained control over which loggers emit debug messages? Here are some possibilities:
(1) Set a filter. .................
When a message is propagated to a logger in the hierarchy first the loggers level is checked. If logger level passes then the logger iterates over every handler attached to the logger first checking the handler level. If the handler level check passes then the filters attached to the handler are run.
Filters are passed the record (i.e. the message), it does not have access to either the logger or handler it's executing within. You can't just set the filter to only pass the records of the classes you want to debug because that would block other important info, warning, error and critical messages from other classes. The filter would have to know about the "global" log level which is in effect and also pass any messages at that level or higher. It's unfortunate the filter cannot know the level of the logger or handler it's executing inside of.
Also logger filters only are applied to the logger they are attached to, i.e. the logger the message was generated on. They do not get applied to any ancestor loggers. That means you can't just set a filter on the root logger. You have to either set the filters on the handlers or on every logger created.
The filter first checks the level of the message record. If it's greater than debug it passes it. For debug messages it checks the set of loggers which have debug messages enabled, if the message record was generated on one of those loggers it passes the record, otherwise it blocks it.
The only question is whether you attach the filter to every logger or to a handful of handlers. The advantage of attaching the filter to every logger is efficiency, the time spent handling the message can be short circuited much sooner if the message is filtered earlier in the process. The advantage of attaching the filter to a handler is simplicity, you only have to do that when a handler is created, not every place in the code where a logger is created.
(2) Conditionally set the level of each logger. ...............................................
When loggers are created a check is performed to see if the logger is in the set of loggers for which debug information is desired, if so it's level is set to DEBUG, otherwise it's set to the global level. One has to recall there really isn't a single global level if you want some handlers to emit info and above, some handlers error and above, etc. In this case if the logger is not in the set of logger's emitting debug the logger level should be set to the next increment above debug level.
A good question to ask would be why not just leave the logger's level unset if it's not in the set of loggers to be debugged? After all it will just inherit the root level right? There are two problems with that. 1) It wold actually inherit the level any ancestor logger and if an ancestor was set to debug you've effectively turned on debugging for all children of that ancestor logger. There are times you might want that behavior, where all your children inherit your level, but there are many cases where that's not the behavior you want. 2) A more pernicious problem exists. The logger your handlers are attached to MUST be set to debug level, otherwise your debug messages will never reach the handlers for output. Thus if you leave a loggers level unset and let it inherit it's effective level from an ancestor it might very well inherit the debug level from the root logger. That means you've completely negated your attempt to selectively set debug logging on specific loggers. Bottom line, you really have to set the level on every logger created if you want fine grained control.
Approach 2 has some distinct performance advantages. First of all filters are not used, this avoids a whole processing step and extra filter function calls on every message. Secondly a logger level check is a simple integer compare which is very efficient. Thirdly the processing of a message can be short circuited very early in the processing pipeline, no ancestor loggers will be invoked and no handlers will be invoked.
The downside is some added complexity at logger creation time. But this is easily mitigated by using a utility function or method to create the logger instead of just calling logger.getLogger().
Like every thing else in computer science which approach you take boils down to a series of trade offs, most around how your code is organized. You might find it easier to set a filter on just one or two handlers. It might be easier to modify the configuration during execution if the logic is centralized in just a filter function, but don't let that sway you too much because it's trivial to iterate over every logger and dynamically reset it's log level.
Now at least you've got a basic understanding of how this stuff hangs together and what your options are. That's not insignificant, when I was first introduced to logging in Java and Python I found it bewildering difficult to get it do what I wanted.
John Dennis <jdennis@redhat.com>
'''
#-------------------------------------------------------------------------------
#------------------------------------------------------------------------------- # Default format
# Maps a logging level name to it's numeric value 'notset' : logging.NOTSET, 'debug' : logging.DEBUG, 'info' : logging.INFO, 'warn' : logging.WARNING, 'warning' : logging.WARNING, 'error' : logging.ERROR, 'critical' : logging.CRITICAL }
#-------------------------------------------------------------------------------
''' Given a iterable of objects containing a logging level return a ordered list (min to max) of unique levels.
:parameters: iterable Iterable yielding objects with a logging level attribute. :returns: Ordered list (min to max) of unique levels. ''' levels = set()
for obj in iterable: level = getattr(obj, 'level', sys.maxint) if level != logging.NOTSET: levels.add(level) levels = list(levels) levels.sort() return levels
''' Given a iterable of objects containing a logging level return the minimum level. If no levels are defined return maxint. set of unique levels.
:parameters: iterable Iterable yielding objects with a logging level attribute. :returns: Ordered list (min to max) of unique levels. '''
''' Given a log level either as a string or integer return a numeric logging level. The following case insensitive names are recognized::
* notset * debug * info * warn * warning * error * critical
A string containing an integer is also recognized, for example ``"10"`` would map to ``logging.DEBUG``
The integer value must be the range [``logging.NOTSET``, ``logging.CRITICAL``] otherwise a value exception will be raised.
:parameters: level basestring or integer, level value to convert :returns: integer level value ''' # Is it a string representation of an integer? # If so convert to an int.
# If it's a string lookup it's name and map to logging level # otherwise validate the integer value is in range. raise ValueError('unknown log level (%s)' % level) raise ValueError('log level (%d) out of range' % level) else: raise TypeError('log level must be basestring or int, got (%s)' % type(level))
#------------------------------------------------------------------------------- ''' Unfortunately the logging Logger and Handler classes do not have a custom __str__() function which converts the object into a human readable string representation. This function takes any object with a level attribute and outputs the objects name with it's associated level. If a name was never set for the object then it's repr is used instead.
:parameters: obj Object with a logging level attribute :returns: string describing the object ''' name = getattr(obj, 'name', repr(obj)) text = '"%s" [level=%s]' % (name, logging.getLevelName(obj.level)) if isinstance(obj, logging.FileHandler): text += ' filename="%s"' % obj.baseFilename return text #------------------------------------------------------------------------------- ''' This class wraps the functionality in the logging module to provide an easier to use API for logging while providing advanced features including a independent namespace. Each application or library wishing to have it's own logging namespace should instantiate exactly one instance of this class and use it to manage all it's logging.
Traditionally (or simplistically) logging was set up with a single global root logger with output handlers bound to it. The global root logger (whose name is the empty string) was shared by all code in a loaded process. The only the global unamed root logger had a level set on it, all other loggers created inherited this global level. This can cause conflicts in more complex scenarios where loaded code wants to maintain it's own logging configuration independent of whomever loaded it's code. By using only a single logger level set on the global root logger it was not possible to have fine grained control over individual logger output. The pattern seen with this simplistic setup has been frequently copied despite being clumsy and awkward. The logging module has the tools available to support a more sophisitcated and useful model, but it requires an overarching framework to manage. This class provides such a framework.
The features of this logging manager are:
* Independent logging namespace.
* Simplifed method to create handlers.
* Simple setup for applications with command line args.
* Sophisitcated handler configuration (e.g. file ownership & permissions)
* Easy fine grained control of logger output (e.g. turning on debug for just 1 or 2 loggers)
* Holistic management of the interrelationships between logging components.
* Ability to dynamically adjust logging configuration in a running process.
An independent namespace is established by creating a independent root logger for this manager (root_logger_name). This root logger is a direct child of the global unamed root logger. All loggers created by this manager will be descendants of this managers root logger. The managers root logger has it's propagate flag set to False which means all loggers and handlers created by this manager will be isolated in the global logging tree.
Log level management: ---------------------
Traditionally loggers inherited their logging level from the root logger. This was simple but made it impossible to independently control logging output from different loggers. If you set the root level to DEBUG you got DEBUG output from every logger in the system, often overwhelming in it's voluminous output. Many times you want to turn on debug for just one class (a common idom is to have one logger per class). To achieve the fine grained control you can either use filters or set a logging level on every logger (see the module documentation for the pros and cons). This manager sets a log level on every logger instead of using level inheritence because it's more efficient at run time.
Global levels are supported via the verbose and debug flags setting every logger level to INFO and DEBUG respectively. Fine grained level control is provided via regular expression matching on logger names (see `configure()` for the details. For example if you want to set a debug level for the foo.bar logger set a regular expression to match it and bind it to the debug level. Note, the global verbose and debug flags always override the regular expression level configuration. Do not set these global flags if you want fine grained control.
The manager maintains the minimum level for all loggers under it's control and the minimum level for all handlers under it's control. The reason it does this is because there is no point in generating debug messages on a logger if there is no handler defined which will output a debug message. Thus when the level is set on a logger it takes into consideration the set of handlers that logger can emit to.
IMPORTANT: Because the manager maintains knowledge about all the loggers and handlers under it's control it is essential you use only the managers interface to modify a logger or handler and not set levels on the objects directly, otherwise the manger will not know to visit every object under it's control when a configuraiton changes (see '`LogManager.apply_configuration()`).
Example Usage::
# Create a log managers for use by 'my_app' log_mgr = LogManager('my_app')
# Create a handler to send error messages to stderr log_mgr.create_log_handlers([dict(stream=sys.stdout, level=logging.ERROR)])
# Create logger for a class class Foo(object): def __init__(self): self.log = log_mgr.get_logger(self)
''' ''' Create a new LogManager instance using root_logger_name as the parent of all loggers maintained by the manager.
Only one log manger should be created for each logging namespace.
:parameters: root_logger_name The name of the root logger. All loggers will be prefixed by this name. configure_state Used by clients of the log manager to track the configuration state, may be any object.
:return: LogManager instance
'''
# Stop loggers and handlers from searching above our root
doc='see log_manager.parse_log_level()` for details on how the level can be specified during assignement.')
''' Reset the default logger level, updates all loggers. Note, the default_level may also be set by assigning to the default_level attribute but that does not update the configure_state, this method is provided as a convenience to simultaneously set the configure_state if so desired.
:parameters: level The new default level for the log manager. See `log_manager.parse_log_level()` for details on how the level can be specified. configure_state If other than None update the log manger's configure_state variable to this object. Clients of the log manager can use configure_state to track the state of the log manager.
''' level = parse_log_level(level) self._default_level = level self.apply_configuration(configure_state)
''' When str() is called on the LogManager output it's state. ''' text = '' text += 'root_logger_name: %s\n' % (self.root_logger_name) text += 'configure_state: %s\n' % (self.configure_state) text += 'default_level: %s\n' % (logging.getLevelName(self.default_level)) text += 'debug: %s\n' % (self.debug) text += 'verbose: %s\n' % (self.verbose)
text += 'number of loggers: %d\n' % (len(self.loggers)) loggers = [logging_obj_str(x) for x in self.loggers.values()] loggers.sort() for logger in loggers: text += ' %s\n' % (logger)
text += 'number of handlers: %d\n' % (len(self.handlers)) handlers = [logging_obj_str(x) for x in self.handlers.values()] handlers.sort() for handler in handlers: text += ' %s\n' % (handler)
text += 'number of logger regexps: %d\n' % (len(self.logger_regexps)) for regexp, level in self.logger_regexps: text += ' "%s" => %s\n' % (regexp, logging.getLevelName(level))
return text
''' The log manager is initialized from key,value pairs in the config dict. This may be called any time to modify the logging configuration at run time.
The supported entries in the config dict are:
default_level The default level applied to a logger when not indivdually configured. The verbose and debug config items override the default level. See `log_manager.parse_log_level()` for details on how the level can be specified. verbose Boolean, if True sets default_level to INFO. debug Boolean, if True sets default_level to DEBUG. logger_regexps List of (regexp, level) tuples. This is a an ordered list regular expressions used to match against a logger name to configure the logger's level. The first regexp in the sequence which matches the logger name will use the the level bound to that regexp to set the logger's level. If no regexp matches the logger name then the logger will be assigned the default_level.
The regular expression comparision is performed with the re.search() function which means the match can be located anywhere in the name string (as opposed to the start of the the string). Do not forget to escape regular expression metacharacters when appropriate. For example dot ('.') is used to seperate loggers in a logging hierarchy path (e.g. a.b.c)
Examples::
# To match exactly the logger a.b.c and set it to DEBUG: logger_regexps = [(r'^a\.b\.c$', 'debug')]
# To match any child of a.b and set it to INFO: logger_regexps = [(r'^a\.b\..*', 'info')]
# To match any leaf logger with the name c and set it to level 5: logger_regexps = [(r'\.c$', 5)] handlers List of handler config dicts or (config, logger) tuples. See `create_log_handlers()` for details of a hanlder config.
The simple form where handlers is a list of dicts each handler is bound to the log mangers root logger (see `create_log_handlers()` optional ``logger`` parameter). If you want to bind each handler to a specific logger other then root handler then group the handler config with a logger in a (config, logger) tuple. The logger may be either a logger name or a logger instance. The following are all valid methods of passing handler configuration.::
# List of 2 config dicts; both handlers bound to root logger [{}, {}]
# List of 2 tuples; first handler bound to logger_name1 # by name, second bound to logger2 by object. [({}, 'logger_name1'), ({}, logger2']
# List of 1 dict, 1 tuple; first bound to root logger, # second bound to logger_name by name [{}, ({}, 'logger_name']
:parameters: config Dict of <key,value> pairs describing the configuration. configure_state If other than None update the log manger's configure_state variable to this object. Clients of the log manager can use configure_state to track the state of the log manager.
'''
except Exception, e: raise ValueError("could not set %s (%s)" % (attr, e))
elif isinstance(item, tuple): if len(item) != 2: raise ValueError('handler tuple must have exactly 2 items, got "%s"' % item) config = item[0] logger = item[1] else: raise TypeError('expected dict or tuple for handler item, got "%s", handlers=%s' % \ type(item), value)
raise TypeError('expected dict for handler config, got "%s"', type(config)) logger = self.get_logger(logger) else: raise TypeError('expected logger name or logger object in %s' % item)
self.default_level = logging.INFO
self.default_level = logging.DEBUG
''' Create new handlers and attach them to a logger (log mangers root logger by default).
*Note, you may also pass the handler configs to `LogManager.configure()`.*
configs is an iterable yielding a dict. Each dict configures a handler. Currently two types of handlers are supported:
* stream * file
Which type of handler is created is determined by the presence of the ``stream`` or ``filename`` in the dict.
Configuration keys: ===================
Handler type keys: ------------------
Exactly of the following must present in the config dict:
stream Use the specified stream to initialize the StreamHandler.
filename Specifies that a FileHandler be created, using the specified filename.
Common keys: ------------
name Set the name of the handler. This is optional but can be useful when examining the logging configuration. For files defaults to ``'file:absolute_path'`` and for streams it defaults to ``'stream:stream_name'``
format Use the specified format string for the handler.
time_zone_converter Log record timestamps are seconds since the epoch in the UTC time zone stored as floating point values. When the formatter inserts a timestamp via the %(asctime)s format substitution it calls a time zone converter on the timestamp which returns a time.struct_time value to pass to the time.strftime function along with the datefmt format conversion string. The time module provides two functions with this signature, time.localtime and time.gmtime which performs a conversion to local time and UTC respectively. time.localtime is the default converter. Setting the time zone converter to time.gmtime is appropriate for date/time strings in UTC. The time_zone_converter attribute may be any function with the correct signature. Or as a convenience you may also pass a string which will select either the time.localtime or the time.gmtime converter. The case insenstive string mappings are::
'local' => time.localtime 'localtime' => time.localtime 'gmt' => time.gmtime 'gmtime' => time.gmtime 'utc' => time.gmtime
datefmt Use the specified time.strftime date/time format when formatting a timestamp via the %(asctime)s format substitution. The timestamp is first converted using the time_zone_converter to either local or UTC
level Set the handler logger level to the specified level. May be one of the following strings: 'debug', 'info', 'warn', 'warning', 'error', 'critical' or any of the logging level constants. Thus level='debug' is equivalent to level=logging.DEBUG. Defaults to self.default_level.
File handler keys: ------------------
filemode Specifies the mode to open the file. Defaults to 'a' for append, use 'w' for write.
permission Set the permission bits on the file (i.e. chmod). Must be a valid integer (e.g. 0660 for rw-rw----)
user Set the user owning the file. May be either a numeric uid or a basestring with a user name in the passwd file.
group Set the group associated with the file, May be either a numeric gid or a basestring with a group name in the groups file.
Examples: ---------
The following shows how to set two handlers, one for a file (ipa.log) at the debug log level and a second handler set to stdout (e.g. console) at the info log level. (One handler sets it level with a simple name, the other with a logging constant just to illustrate the flexibility) ::
# Get a root logger log_mgr = LogManger('my_app')
# Create the handlers log_mgr.create_log_handlers([dict(filename='my_app.log', level='info', user='root', group='root', permission=0600, time_zone_converter='utc', datefmt='%Y-%m-%dT%H:%M:%SZ', # ISO 8601 format='<%(levelname)s> [%(asctime)s] module=%(name)s "%(message)s"'), dict(stream=sys.stdout, level=logging.ERROR, format='%(levelname)s: %(message)s')])
# Create a logger for my_app.foo.bar foo_bar_log = log_mgr.get_logger('foo.bar')
root_logger.info("Ready to process requests") foo_bar_log.error("something went boom")
In the file my_app.log you would see::
<INFO> [2011-10-26T01:39:00Z] module=my_app "Ready to process requests" <ERROR> [2011-10-26T01:39:00Z] module=may_app.foo.bar "something went boom"
On the console you would see::
ERROR: something went boom
:parameters: configs Sequence of dicts (any iterable yielding a dict). Each dict creates one handler and contains the configuration parameters used to create that handler. logger If unspecified the handlers will be attached to the LogManager.root_logger, otherwise the handlers will be attached to the specified logger. configure_state If other than None update the log manger's configure_state variable to this object. Clients of the log manager can use configure_state to track the state of the log manager.
:return: The list of created handers. '''
# Iterate over handler configurations. # File or stream handler? raise ValueError("both filename and stream are specified, must be one or the other, config: %s" % cfg)
# Set the handler name name = 'file:%s' % (path)
# Path should now exist, set ownership and permissions if requested.
# Set uid, gid (e.g. chmod) if isinstance(user, basestring): pw = pwd.getpwnam(user) uid = pw.pw_uid elif isinstance(user, int): uid = user else: raise TypeError("user (%s) is not int or basestring" % user) if isinstance(group, basestring): pw = pwd.getpwnam(group) gid = pw.pw_gid elif isinstance(group, int): gid = group else: raise TypeError("group (%s) is not int or basestring" % group) if uid is None: uid = -1 if gid is None: gid = -1 os.chown(path, uid, gid)
# Set file permissions (e.g. mode) os.chmod(path, permission) else: raise ValueError("neither file nor stream specified in config: %s" % cfg)
# Set the handler name name = 'stream:%s' % (stream)
# Add the handler
# Configure message formatting on the handler 'localtime' : time.localtime, 'gmt' : time.gmtime, 'gmtime' : time.gmtime, 'utc' : time.gmtime}.get(time_zone_converter.lower()) raise ValueError("invalid time_zone_converter name (%s)" % \ time_zone_converter) elif callable(time_zone_converter): converter = time_zone_converter else: raise ValueError("time_zone_converter must be basestring or callable, not %s" % \ type(time_zone_converter))
# Set the logging level except Exception, e: print >>sys.stderr, 'could not set handler log level "%s" (%s)' % (level, e) level = None
raise ValueError('handler "%s" already exists' % handler.name)
''' Given a handler name return the handler object associated with it.
:parameters: handler_name Name of the handler to look-up.
:returns: The handler object associated with the handler name. ''' raise KeyError('handler "%s" is not defined' % handler_name)
''' Given a handler name, set the handler's level, return previous level.
:parameters: handler_name Name of the handler to look-up. level The new level for the handler. See `log_manager.parse_log_level()` for details on how the level can be specified. configure_state If other than None update the log manger's configure_state variable to this object. Clients of the log manager can use configure_state to track the state of the log manager.
:returns: The handler's previous level ''' handler = self.get_handler(handler_name) level = parse_log_level(level) prev_level = handler.level handler.setLevel(level) self.apply_configuration(configure_state) return prev_level
''' Given a handler return a list of loggers that hander is bound to.
:parameters: handler The name of a handler or a handler object.
:returns: List of loggers with the handler is bound to. '''
handler = self.get_handler(handler) raise ValueError('handler "%s" is not managed by this log manager' % \ logging_obj_str(handler)) else: raise TypeError('handler must be basestring or Handler object, got %s' % type(handler))
''' Remove the named handler. If logger is unspecified the handler will be removed from all managed loggers, otherwise it will be removed from only the specified logger.
:parameters: handler The name of the handler to be removed or the handler object. logger If unspecified the handler is removed from all loggers, otherwise the handler is removed from only this logger. configure_state If other than None update the log manger's configure_state variable to this object. Clients of the log manager can use configure_state to track the state of the log manager. '''
elif not isinstance(handler, logging.Handler): raise TypeError('handler must be basestring or Handler object, got %s' % type(handler))
raise ValueError('handler "%s" does not have a name' % logging_obj_str(handler))
else: if not logger in loggers: raise ValueError('handler "%s" is not bound to logger "%s"' % \ (handler_name, logging_obj_str(logger))) logger.removeHandler(handler) if len(loggers) == 1: del self.handlers[handler_name]
''' Using the log manager's internal configuration state apply the configuration to all the objects managed by the log manager.
:parameters: configure_state If other than None update the log manger's configure_state variable to this object. Clients of the log manager can use configure_state to track the state of the log manager.
'''
''' Given a logger name return it's level as defined by the `LogManager` configuration.
:parameters: name logger name :returns: log level ''' if re.search(regexp, name): level = config_level break
''' Return the set of unique handlers visible to this logger.
:parameters: logger The logger whose visible and enabled handlers will be returned.
:return: Set of handlers '''
else:
''' Return the minimum handler level of all the handlers the logger is exposed to.
:parameters: logger The logger whose handlers will be examined.
:return: The minimum of all the handler's levels. If no handlers are defined sys.maxint will be returned. '''
''' Based on the current configuration maintained by the log manager set this logger's level.
If the level specified for this logger by the configuration is less than the minimum level supported by the output handlers the logger is exposed to then adjust the logger's level higher to the minimum handler level. This is a performance optimization, no point in emitting a log message if no handlers will ever output it.
:parameters: logger The logger whose level is being configured.
:return: The level actually set on the logger. '''
''' Return the logger for an object or a name. If the logger already exists return the existing instance otherwise create the logger.
The who parameter may be either a name or an object. Loggers are identified by a name but because loggers are usually bound to a class this method is optimized to handle that case. If who is an object:
* The name object's module name (dot seperated) and the object's class name.
* Optionally the logging output methods can be bound to the object if bind_logger_names is True.
Otherwise if who is a basestring it is used as the logger name.
In all instances the root_logger_name is prefixed to every logger created by the manager.
:parameters: who If a basestring then use this as the logger name, prefixed with the root_logger_name. Otherwise who is treated as a class instance. The logger name is formed by prepending the root_logger_name to the module name and then appending the class name. All name components are dot seperated. Thus if the root_logger_name is 'my_app', the class is ParseFileConfig living in the config.parsers module the logger name will be: ``my_app.config.parsers.ParseFileConfig``. bind_logger_names If true the class instance will have the following bound to it: ``log``, ``debug()``, ``info()``, ``warning()``, ``error()``, ``exception()``, ``critical()``. Where log is the logger object and the others are the loggers output methods. This is a convenience which allows you emit logging messages directly, for example::
self.debug('%d names defined', self.num_names).
:return: The logger matching the name indicated by who. If the logger pre-existed return that instance otherwise create the named logger return it. '''
else:
else:
# If logger not in our cache then create and initialize the logger.
raise ValueError('%s is already bound to %s' % (method, repr(who)))
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