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% These apply to all modules, and may be given more than once:
\moduleauthor{Vinay Sajip}{vinay_sajip@red-dove.com}
\sectionauthor{Skip Montanaro}{skip@pobox.com}
\sectionauthor{Vinay Sajip}{vinay_sajip@red-dove.com}
\modulesynopsis{Logging module for Python based on PEP 282.}
There is a need for a standard logging system in Python, as documented in
{}\pep{282} and enthusiastically endorsed by Guido van Rossum in the
{}\citetitle[http://www.python.org/doc/essays/pepparade.html]{Parade of the
PEPs}. By a happy coincidence, the package described here was already in
development and fairly close in intent and design to the description in the
aforementioned PEP, borrowing as it did heavily from JSR-47 (now JDK 1.4's
java.util.logging package) and
{}\ulink{log4j}{http://jakarta.apache.org/log4j/}. This section page
describes it in more detail.
This package owes its greatest debt to Apache
{}\ulink{log4j}{http://jakarta.apache.org/log4j/}. Due notice was also taken
of log4j's comprehensive
{}\ulink{critique}{http://jakarta.apache.org/log4j/docs/critique.html} of
JSR-47. This package bears a close resemblance to log4j, but is not a close
translation (as, for example, {}\ulink{log4p}{http://log4p.sourceforge.net/}
appears to be).
\subsection{Functions}
The \module{logging} module defines the following functions:
\begin{funcdesc}{getLevelName}{level}
Return the textual representation of logging level \var{level}.
If the level is one of the predefined levels (\var{CRITICAL}, \var{ERROR},
{}\var{WARN}, \var{INFO}, \var{DEBUG}) then you get the corresponding
string. If you have associated levels with names using
{}\function{addLevelName} then the name you have associated with \var{level}
is returned. Otherwise, the string "Level \%s" \% level is returned.
\indexii{Errors}{logging}
\versionadded{2.3}
This module defines functions and classes which implement a flexible
error logging system for applications.
Logging is performed by calling methods on instances of the
\class{Logger} class (hereafter called \dfn{loggers}). Each instance has a
name, and they are conceptually arranged in a name space hierarchy
using dots (periods) as separators. For example, a logger named
"scan" is the parent of loggers "scan.text", "scan.html" and "scan.pdf".
Logger names can be anything you want, and indicate the area of an
application in which a logged message originates.
Logged messages also have levels of importance associated with them.
The default levels provided are \constant{DEBUG}, \constant{INFO},
\constant{WARNING}, \constant{ERROR} and \constant{CRITICAL}. As a
convenience, you indicate the importance of a logged message by calling
an appropriate method of \class{Logger}. The methods are
\method{debug}, \method{info}, \method{warning}, \method{error} and
\method{critical}, which mirrors the default levels. You are not
constrained to use these levels - you can specify your own and use a
more general \class{Logger} method, \method{log}, which takes an
explicit level argument.
Levels can also be associated with loggers, being set either by the
developer or through loading a saved logging configuration. When a
logging method is called on a logger, the logger compares its own
level with the level associated with the method call. If the logger's
level is higher than the method call's, no logging message is actually
generated. This is the basic mechanism controlling the verbosity of
logging output.
Logging messages are encoded as instances of the \class{LogRecord} class.
When a logger decides to actually log an event, an \class{LogRecord}
instance is created from the logging message.
Logging messages are subjected to a dispatch mechanism through the
use of \dfn{handlers}, which are instances of subclasses of the
\class{Handler} class. Handlers are responsible for ensuring that a logged
message (in the form of a \class{LogRecord}) ends up in a particular
location (or set of locations) which is useful for the target audience for
that message (e.g. end users, support desk staff, system administrators,
developers). Handlers are passed \class{LogRecord} instances intended for
particular destinations. Each logger can have zero, one or more handlers
associated with it (via the \method{addHandler} method of \class{Logger}).
In addition to any handlers directly associated with a logger,
\emph{all handlers associated with all ancestors of the logger} are called
upon to dispatch the message.
Just as for loggers, handlers can have levels associated with them.
A handler's level acts as a filter in the same way as a logger's level does.
If a handler decides to actually dispatch an event, the \method{emit} method
is used to send the message to its destination. Most user-defined subclasses
of \class{Handler} will need to override this \method{emit}.
In addition to the base \class{Handler} class, many useful subclasses
are provided:
\begin{enumerate}
\item \class{StreamHandler} instances send error messages to
streams (file-like objects).
\item \class{FileHandler} instances send error messages to disk
files.
\item \class{RotatingFileHandler} instances send error messages to disk
files, with support for maximum log file sizes and log file rotation.
\item \class{SocketHandler} instances send error messages to
TCP/IP sockets.
\item \class{DatagramHandler} instances send error messages to UDP
sockets.
\item \class{SMTPHandler} instances send error messages to a
designated email address.
\item \class{SysLogHandler} instances send error messages to a
Unix syslog, possibly on a remote machine.
\item \class{NTEventLogHandler} instances send error messages to a
Windows NT/2000/XP event log.
\item \class{MemoryHandler} instances send error messages to a
buffer in memory, which is flushed whenever specific criteria are
met.
\item \class{HTTPHandler} instances send error messages to an
HTTP server using either GET or POST semantics.
\end{enumerate}
The \class{StreamHandler} and \class{FileHandler} classes are defined
in the core logging package. The other handlers are defined in a sub-
module, \module{logging.handlers}. (There is also another sub-module,
\module{logging.config}, for configuration functionality.)
Logged messages are formatted for presentation through instances of the
\class{Formatter} class. They are initialized with a format string
suitable for 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.
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 \method{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
children are allowed through the filter, and all others dropped.
In addition to the classes described above, there are a number of module-
level functions.
\begin{funcdesc}{getLogger}{\optional{name}}
Return a logger with the specified name or, if no name is specified, return
a logger which is the root logger of the hierarchy.
All calls to this function with a given name return the same logger instance.
This means that logger instances never need to be passed between different
parts of an application.
\end{funcdesc}
\begin{funcdesc}{addLevelName}{level, levelName}
Associate \var{levelName} with \var{level}. This is used when converting
levels to text during message formatting.
\begin{funcdesc}{debug}{msg\optional{, *args\optional{, **kwargs}}}
Logs a message with level \constant{DEBUG} on the root logger.
The \var{msg} is the message format string, and the \var{args} are the
arguments which are merged into \var{msg}. The only keyword argument in
\var{kwargs} which is inspected is \var{exc_info} which, if it does not
evaluate as false, causes exception information (via a call to
\method{sys.exc_info()}) to be added to the logging message.
\end{funcdesc}
\begin{funcdesc}{setLoggerClass}{klass}
Set the class to be used when instantiating a logger. The class should
define \code{__init__()} such that only a name argument is required, and the
{}\code{__init__()} should call Logger.__init__()
\end{funcdesc}
\begin{funcdesc}{basicConfig}{}
Do basic configuration for the logging system by creating a
{}\class{StreamHandler} with a default {}\class{Formatter} and adding it to
the root logger.
\begin{funcdesc}{info}{msg\optional{, *args\optional{, **kwargs}}}
Logs a message with level \constant{INFO} on the root logger.
The arguments are interpreted as for \function{debug()}.
\end{funcdesc}
\begin{funcdesc}{getLogger}{\optional{name=None}}
Return a logger with the specified name, creating it if necessary. If no
name is specified, return the root logger.
\begin{funcdesc}{warning}{msg\optional{, *args\optional{, **kwargs}}}
Logs a message with level \constant{WARNING} on the root logger.
The arguments are interpreted as for \function{debug()}.
\end{funcdesc}
\begin{funcdesc}{critical}{msg, *args, **kwargs}
Log a message with severity \code{CRITICAL} on the root logger.
\begin{funcdesc}{error}{msg\optional{, *args\optional{, **kwargs}}}
Logs a message with level \constant{ERROR} on the root logger.
The arguments are interpreted as for \function{debug()}.
\end{funcdesc}
\begin{funcdesc}{error}{msg, *args, **kwargs}
Log a message with severity \var{ERROR} on the root logger.
\begin{funcdesc}{critical}{msg\optional{, *args\optional{, **kwargs}}}
Logs a message with level \constant{CRITICAL} on the root logger.
The arguments are interpreted as for \function{debug()}.
\end{funcdesc}
\begin{funcdesc}{exception}{msg, *args}
Log a message with severity \code{ERROR} on the root logger,
with exception information.
\begin{funcdesc}{exception}{msg\optional{, *args}}
Logs a message with level \constant{ERROR} on the root logger.
The arguments are interpreted as for \function{debug()}. Exception info
is added to the logging message. This function should only be called
from an exception handler.
\end{funcdesc}
\begin{funcdesc}{warn}{msg, *args, **kwargs}
Log a message with severity \code{WARN} on the root logger.
\begin{funcdesc}{disable}{lvl}
Provides an overriding level \var{lvl} for all loggers which takes
precedence over the logger's own level. When the need arises to
temporarily throttle logging output down across the whole application,
this function can be useful.
\end{funcdesc}
\begin{funcdesc}{info}{msg, *args, **kwargs}
Log a message with severity \code{INFO} on the root logger.
\begin{funcdesc}{addLevelName}{lvl, levelName}
Associates level \var{lvl} with text \var{levelName} in an internal
dictionary, which is used to map numeric levels to a textual
representation, for example when a \class{Formatter} formats a message.
This function can also be used to define your own levels. The only
constraints are that all levels used must be registered using this
function, levels should be positive integers and they should increase
in increasing order of severity.
\end{funcdesc}
\begin{funcdesc}{debug}{msg, *args, **kwargs}
Log a message with severity \code{DEBUG} on the root logger.
\begin{funcdesc}{getLevelName}{lvl}
Returns the textual representation of logging level \var{lvl}. If the
level is one of the predefined levels \constant{CRITICAL},
\constant{ERROR}, \constant{WARNING}, \constant{INFO} or \constant{DEBUG}
then you get the corresponding string. If you have associated levels
with names using \function{addLevelName()} then the name you have associated
with \var{lvl} is returned. Otherwise, the string "Level \%s" \% lvl is
returned.
\end{funcdesc}
\begin{funcdesc}{disable}{level}
Disable all logging calls less severe than \code{level}.
\begin{funcdesc}{basicConfig}{}
Does basic configuration for the logging system by creating a
\class{StreamHandler} with a default \class{Formatter} and adding it to
the root logger. The functions \function{debug()}, \function{info()},
\function{warning()}, \function{error()} and \function{critical()} will call
\function{basicConfig()} automatically if no handlers are defined for the
root logger.
\end{funcdesc}
\begin{funcdesc}{shutdown}{}
Perform any cleanup actions in the logging system (e.g. flushing buffers).
Should be called at application exit.
Informs the logging system to perform an orderly shutdown by flushing and
closing all handlers.
\end{funcdesc}
\begin{funcdesc}{setLoggerClass}{klass}
Tells the logging system to use the class \var{klass} when instantiating a
logger. The class should define \method{__init__()} such that only a name
argument is required, and the \method{__init__()} should call
\method{Logger.__init__()}. This function is typically called before any
loggers are instantiated by applications which need to use custom logger
behavior.
\end{funcdesc}
\subsection{Logger Objects}
\subsection{Data}
The \module{logging} module defines the following data objects:
\begin{datadesc}{root}
The default logger.
\end{datadesc}
\begin{datadesc}{BASIC_FORMAT}
The default message format.
\end{datadesc}
\begin{datadesc}{CRITICAL}
The \code{CRITICAL} level.
\end{datadesc}
\begin{datadesc}{FATAL}
The \code {FATAL} level. A synonym for \code{CRITICAL}.
\end{datadesc}
\begin{datadesc}{WARN}
The \code {WARN} level.
\end{datadesc}
\begin{datadesc}{INFO}
The \code{INFO} level.
\end{datadesc}
\begin{datadesc}{DEBUG}
The \code{DEBUG} level.
\end{datadesc}
\begin{datadesc}{NOTSET}
The \code{NOTSET} level.
\end{datadesc}
\begin{datadesc}{raiseExceptions}
Indicates whether exceptions during handling should be propagated. True by
default.
Loggers have the following attributes and methods. Note that Loggers are
never instantiated directly, but always through the module-level function
\function{logging.getLogger(name)}.
\begin{datadesc}{propagate}
If this evaluates to false, logging messages are not passed by this
logger or by child loggers to higher level (ancestor) loggers. The
constructor sets this attribute to 1.
\end{datadesc}
\subsection{Classes}
The \module{logging} module defines the following classes:
\begin{classdesc}{Formatter}{\optional{fmt=None\optional{, datefmt=None}}}
Formatters need to know how a LogRecord is constructed. They are responsible
for converting a LogRecord to (usually) a string which can be interpreted by
either a human or an external system. The base Formatter allows a formatting
string to be specified. If none is supplied, the default value of
\code{"\%s(message)\e n"} is used.
The Formatter can be initialized with a format string which makes use of
knowledge of the LogRecord attributes - e.g. the default value mentioned
above makes use of the fact that the user's message and arguments are pre-
formatted into a LogRecord's message attribute. Currently, the useful
attributes in a LogRecord are described by:
\begin{description}
\item[\%(name)s]{Name of the logger (logging channel)}
\item[\%(levelno)s]{Numeric logging level for the message (DEBUG, INFO,
WARN, ERROR, CRITICAL)}
\item[\%(levelname)s]{Text logging level for the message ("DEBUG", "INFO",
"WARN", "ERROR", "CRITICAL")}
\item[\%(pathname)s]{Full pathname of the source file where the logging
call was issued (if available)}
\item[\%(filename)s]{Filename portion of pathname}
\item[\%(module)s]{Module (name portion of filename)}
\item[\%(lineno)d]{Source line number where the logging call was issued
(if available)}
\item[\%(created)f]{Time when the LogRecord was created (time.time()
return value)}
\item[\%(asctime)s]{Textual time when the LogRecord was created}
\item[\%(msecs)d]{Millisecond portion of the creation time}
\item[\%(relativeCreated)d]{Time in milliseconds when the LogRecord was
created, relative to the time the logging module was loaded (typically at
application startup time)}
\item[\%(thread)d]{Thread ID (if available)}
\item[\%(message)s]{The result of record.getMessage(), computed just as the
record is emitted}
\end{description}
\end{classdesc}
\begin{methoddesc}{format}{self, record}
The record's attribute dictionary is used as the operand to a string
formatting operation which yields the returned string. Before formatting
the dictionary, a couple of preparatory steps are carried out. The message
attribute of the record is computed using \code{LogRecord.getMessage()}. If
the formatting string contains "\%(asctime)", \code{formatTime()} is called
to format the event time. If there is exception information, it is
formatted using \code{formatException()} and appended to the message.
\begin{methoddesc}{setLevel}{lvl}
Sets the threshold for this logger to \var{lvl}. Logging messages
which are less severe than \var{lvl} will be ignored. When a logger is
created, the level is set to \constant{ALL} (which causes all messages
to be processed).
\end{methoddesc}
\begin{methoddesc}{formatException}{self, ei}
Format the specified exception information as a string. This default
implementation just uses \code{traceback.print_exception()}
\begin{methoddesc}{isEnabledFor}{lvl}
Indicates if a message of severity \var{lvl} would be processed by
this logger. This method checks first the module-level level set by
\function{logging.disable(lvl)} and then the logger's effective level as
determined by \method{getEffectiveLevel()}.
\end{methoddesc}
\begin{methoddesc}{formatTime}{self, record\optional{, datefmt=None}}
This method should be called from \code{format()} by a formatter which wants
to make use of a formatted time. This method can be overridden in formatters
to provide for any specific requirement, but the basic behaviour is as
follows: if datefmt (a string) is specified, it is used with time.strftime()
to format the creation time of the record. Otherwise, the ISO8601 format is
used. The resulting string is returned. This function uses a
user-configurable function to convert the creation time to a tuple. By
default, \code{time.localtime()} is used; to change this for a particular
formatter instance, set the 'converter' attribute to a function with the
same signature as \code{time.localtime()} or \code{time.gmtime()}. To change
it for all formatters, for example if you want all logging times to be shown
in GMT, set the 'converter' attribute in the \class{Formatter} class.
\begin{methoddesc}{getEffectiveLevel}{}
Indicates the effective level for this logger. If a value other than
\constant{ALL} has been set using \method{setLevel()}, it is returned.
Otherwise, the hierarchy is traversed towards the root until a value
other than \constant{ALL} is found,and that value is returned.
\end{methoddesc}
\begin{classdesc}{Filterer}{}
A base class for loggers and handlers which allows them to share common
code.
\end{classdesc}
\begin{methoddesc}{addFilter}{filter}
Add the specified filter to this handler.
\begin{methoddesc}{debug}{msg\optional{, *args\optional{, **kwargs}}}
Logs a message with level \constant{DEBUG} on this logger.
The \var{msg} is the message format string, and the \var{args} are the
arguments which are merged into \var{msg}. The only keyword argument in
\var{kwargs} which is inspected is \var{exc_info} which, if it does not
evaluate as false, causes exception information (via a call to
\method{sys.exc_info()}) to be added to the logging message.
\end{methoddesc}
\begin{methoddesc}{filter}{self, record}
Determine if a record is loggable by consulting all the filters. The default
is to allow the record to be logged; any filter can veto this and the record
is then dropped. Returns a boolean value.
\begin{methoddesc}{info}{msg\optional{, *args\optional{, **kwargs}}}
Logs a message with level \constant{INFO} on this logger.
The arguments are interpreted as for \method{debug()}.
\end{methoddesc}
\begin{methoddesc}{removeFilter}{filter}
Remove the specified filter from this handler.
\begin{methoddesc}{warning}{msg\optional{, *args\optional{, **kwargs}}}
Logs a message with level \constant{WARNING} on this logger.
The arguments are interpreted as for \method{debug()}.
\end{methoddesc}
\begin{classdesc}{BufferingFormatter}{\optional{linefmt=None}}
A formatter suitable for formatting a number of records. Optionally specify
a formatter which will be used to format each individual record.
\end{classdesc}
\begin{methoddesc}{format}{records}
Format the specified records and return the result as a string.
\begin{methoddesc}{error}{msg\optional{, *args\optional{, **kwargs}}}
Logs a message with level \constant{ERROR} on this logger.
The arguments are interpreted as for \method{debug()}.
\end{methoddesc}
\begin{methoddesc}{formatFooter}{records}
Return the footer string for the specified records.
\begin{methoddesc}{critical}{msg\optional{, *args\optional{, **kwargs}}}
Logs a message with level \constant{CRITICAL} on this logger.
The arguments are interpreted as for \method{debug()}.
\end{methoddesc}
\begin{methoddesc}{formatHeader}{records}
Return the header string for the specified records.
\begin{methoddesc}{log}{lvl, msg\optional{, *args\optional{, **kwargs}}}
Logs a message with level \var{lvl} on this logger.
The other arguments are interpreted as for \method{debug()}.
\end{methoddesc}
\begin{classdesc}{BufferingHandler}{capacity}
A handler class which buffers logging records in memory. Whenever each
record is added to the buffer, a check is made to see if the buffer should
be flushed. If it should, then \code{flush()} is expected to do the needful.
The handler is initialized with the buffer size.
\end{classdesc}
\begin{methoddesc}{emit}{record}
Append the record. If \code{shouldFlush()} tells us to, call \code{flush()}
to process the buffer.
\begin{methoddesc}{exception}{msg\optional{, *args}}
Logs a message with level \constant{ERROR} on this logger.
The arguments are interpreted as for \method{debug()}. Exception info
is added to the logging message. This method should only be called
from an exception handler.
\end{methoddesc}
\begin{methoddesc}{flush}{}
Override to implement custom flushing behaviour. This version just zaps the
buffer to empty.
\begin{methoddesc}{addFilter}{filt}
Adds the specified filter \var{filt} to this logger.
\end{methoddesc}
\begin{methoddesc}{shouldFlush}{record}
Returns true if the buffer is up to capacity. This method can be overridden
to implement custom flushing strategies.
\begin{methoddesc}{removeFilter}{filt}
Removes the specified filter \var{filt} from this logger.
\end{methoddesc}
\begin{classdesc}{DatagramHandler}{host,port}
A handler class which writes logging records, in pickle format, to a
datagram socket. Note that the very simple wire protocol used means that
packet sizes are expected to be encodable within 16 bits (i.e. < 32767
bytes).
Initializes the handler with a specific \code{host} and \code{port}.
\end{classdesc}
\begin{methoddesc}{makeSocket}{}
The factory method of SocketHandler is here overridden to create a UDP
socket (SOCK_DGRAM).
\begin{methoddesc}{filter}{record}
Applies this logger's filters to the record and returns a true value if
the record is to be processed.
\end{methoddesc}
\begin{methoddesc}{send}{s}
Send a pickled string to a socket. This function allows for partial sends
which can happen when the network is busy.
\begin{methoddesc}{addHandler}{hdlr}
Adds the specified handler \var{hdlr} to this logger.
\end{methoddesc}
\begin{classdesc}{FileHandler}{filename\optional{, mode='a+'}}
A handler class which writes formatted logging records to disk files. The
specified file is opened and used as the stream for logging. By default,
the file grows indefinitely. You can call \code{setRollover()} to allow the
file to rollover at a predetermined size.
\end{classdesc}
\begin{methoddesc}{close}{}
Closes the stream.
\begin{methoddesc}{removeHandler}{hdlr}
Removes the specified handler \var{hdlr} from this logger.
\end{methoddesc}
\begin{methoddesc}{doRollover}{}
Do a rollover, as described in \code{setRollover()}.
\begin{methoddesc}{findCaller}{}
Finds the caller's source filename and line number. Returns the filename
and line number as a 2-element tuple.
\end{methoddesc}
\begin{methoddesc}{emit}{record}
Output the record to the file, catering for rollover as described
in \code{setRollover()}.
\begin{methoddesc}{handle}{record}
Handles a record by passing it to all handlers associated with this logger
and its ancestors (until a false value of \var{propagate} is found).
This method is used for unpickled records received from a socket, as well
as those created locally. Logger-level filtering is applied using
\method{filter()}.
\end{methoddesc}
\begin{methoddesc}{setRollover}{maxBytes, backupCount}
Set the rollover parameters so that rollover occurs whenever the current log
file is nearly \var{maxBytes} in length. If \var{backupCount} is >= 1, the
system will successively create new files with the same pathname as the base
file, but with extensions ".1", ".2" etc. appended to it. For example, with
a \var{backupCount} of 5 and a base file name of "app.log", you would get
"app.log", "app.log.1", "app.log.2", ... through to "app.log.5". When the
last file reaches its size limit, the logging reverts to "app.log" which is
truncated xto zero length. If maxBytes is zero, rollover never occurs.
\begin{methoddesc}{makeRecord}{name, lvl, fn, lno, msg, args, exc_info}
This is a factory method which can be overridden in subclasses to create
specialized \class{LogRecord} instances.
\end{methoddesc}
\begin{classdesc}{Filter}{\optional{name=''}}
The base filter class. \class{Logger} and \class{Handler} instances can
optionally use \class{Filter} instances to filter records as desired. The
base filter class only allows events which are below a certain point in the
logger hierarchy. For example, a filter initialized with "A.B" will allow
events logged by loggers "A.B", "A.B.C", "A.B.C.D", "A.B.D" etc. but not
"A.BB", "B.A.B" etc. If initialized with the empty string, all events are
passed.
The instance is initialized with the name of the logger which, together with
its children, will have its events allowed through the filter. If no name is
specified, allow every event.
\subsection{Handler Objects}
\end{classdesc}
\begin{methoddesc}{filter}{record}
Is the specified record to be logged? Returns 0 for no, nonzero for yes. If
deemed appropriate, the record may be modified in-place.
Handlers have the following attributes and methods. Note that a Handler is
never instantiated directly; this class acts as a base for more useful
subclasses. However, the \method{__init__()} in subclasses needs to call
\method{Handler.__init__()}.
\begin{methoddesc}{__init__}{level=\constant{ALL}}
Initializes the \class{Handler} instance by setting its level, setting
the list of filters to the empty list and creating a lock (using
\method{getLock()}) for serializing access to an I/O mechanism.
\end{methoddesc}
\begin{classdesc}{HTTPHandler}{host, url\optional{, method='GET'}}
A class which sends records to a Web server, using either GET or POST
semantics. The instance is initialized with the \var{host}, the request
\var{url}, and the \var{method} ("GET" or "POST")
\end{classdesc}
\begin{methoddesc}{emit}{record}
Send the \var{record} to the Web server as an URL-encoded dictionary
\begin{methoddesc}{createLock}{}
Initializes a thread lock which can be used to serialize access to
underlying I/O functionality which may not be threadsafe.
\end{methoddesc}
\begin{classdesc}{Handler}{\optional{level=0}}
The base handler class. Acts as a placeholder which defines the Handler
interface. \class{Handler} instances can optionally use \class{Formatter}
instances to format records as desired. By default, no formatter is
specified; in this case, the 'raw' message as determined by record.message
is logged. Initializes the instance - basically setting the formatter to
None and the filter list to empty.
XXX - what does the level do?
\end{classdesc}
\begin{methoddesc}{acquire}{}
Acquire the I/O thread lock.
Acquires the thread lock created with \method{createLock()}.
\end{methoddesc}
\begin{methoddesc}{close}{}
Tidy up any resources used by the handler. This version does nothing and is
intended to be implemented by subclasses.
\begin{methoddesc}{release}{}
Releases the thread lock acquired with \method{acquire()}.
\end{methoddesc}
\begin{methoddesc}{createLock}{}
Acquire a thread lock for serializing access to the underlying I/O.
\begin{methoddesc}{setLevel}{lvl}
Sets the threshold for this handler to \var{lvl}. Logging messages which are
less severe than \var{lvl} will be ignored. When a handler is created, the
level is set to \constant{ALL} (which causes all messages to be processed).
\end{methoddesc}
\begin{methoddesc}{setFormatter}{form}
Sets the \class{Formatter} for this handler to \var{form}.
\end{methoddesc}
\begin{methoddesc}{emit}{record}
\begin{methoddesc}{addFilter}{filt}
Adds the specified filter \var{filt} to this handler.
\end{methoddesc}
Do whatever it takes to actually log the specified logging record. This
version is intended to be implemented by subclasses and so raises a
\exception{NotImplementedError}.
\begin{methoddesc}{removeFilter}{filt}
Removes the specified filter \var{filt} from this handler.
\end{methoddesc}
\begin{methoddesc}{filter}{record}
Applies this handler's filters to the record and returns a true value if
the record is to be processed.
\end{methoddesc}
\begin{methoddesc}{flush}{}
Ensure all logging output has been flushed. This version does nothing and is
intended to be implemented by subclasses.
Ensure all logging output has been flushed. This version does
nothing and is intended to be implemented by subclasses.
\end{methoddesc}
\begin{methoddesc}{format}{record}
Do formatting for a \var{record} - if a formatter is set, use it.
Otherwise, use the default formatter for the module.
\begin{methoddesc}{close}{}
Tidy up any resources used by the handler. This version does
nothing and is intended to be implemented by subclasses.
\end{methoddesc}
\begin{methoddesc}{handle}{record}
Conditionally emit the specified logging \var{record}, depending on filters
which may have been added to the handler. Wrap the actual emission of the
record with acquisition/release of the I/O thread lock.
Conditionally emits the specified logging record, depending on
filters which may have been added to the handler. Wraps the actual
emission of the record with acquisition/release of the I/O thread
lock.
\end{methoddesc}
\begin{methoddesc}{handleError}{}
This method should be called from handlers when an exception is encountered
during an \code{emit()} call. By default it does nothing, because by default
{}\var{raiseExceptions} is false, which means that exceptions get silently
ignored. This is what is mostly wanted for a logging system - most users
will not care about errors in the logging system, they are more interested
in application errors. You could, however, replace this with a custom
This method should be called from handlers when an exception is
encountered during an emit() call. By default it does nothing,
which means that exceptions get silently ignored. This is what is
mostly wanted for a logging system - most users will not care
about errors in the logging system, they are more interested in
application errors. You could, however, replace this with a custom
handler if you wish.
XXX looks to me like raiseExceptions defaults to 1.
\end{methoddesc}
\begin{methoddesc}{release}{}
Release the I/O thread lock.
\end{methoddesc}
\begin{methoddesc}{setFormatter}{formatter}
Set the \var{formatter} for this handler.
\end{methoddesc}
\begin{methoddesc}{setLevel}{level}
Set the logging \var{level} of this handler.
\begin{methoddesc}{format}{record}
Do formatting for a record - if a formatter is set, use it.
Otherwise, use the default formatter for the module.
\end{methoddesc}
\begin{classdesc}{LogRecord}{name,lvl,pathname,lineno,msg,args,exc_info}
\class{LogRecord} instances are created every time something is logged. They
contain all the information pertinent to the event being logged. The main
information passed in is in msg and args, which are combined using
\code{str(msg) \% args} to create the message field of the record. The
record also includes information such as when the record was created, the
source line where the logging call was made, and any exception information
to be logged.
\end{classdesc}
\begin{methoddesc}{getMessage}{}
Return the message for this LogRecord, merging any user-supplied arguments
with the message.
\begin{methoddesc}{emit}{record}
Do whatever it takes to actually log the specified logging record.
This version is intended to be implemented by subclasses and so
raises a \exception{NotImplementedError}.
\end{methoddesc}
\begin{classdesc}{Logger}{name\optional{, level=0}}
Instances of the \class{Logger} class represent a single logging channel. A
"logging channel" indicates an area of an application. Exactly how an "area"
is defined is up to the application developer. Since an application can have
any number of areas, logging channels are identified by a unique
string. Application areas can be nested (e.g. an area of "input processing"
might include sub-areas "read CSV files", "read XLS files" and "read
Gnumeric files"). To cater for this natural nesting, channel names are
organized into a namespace hierarchy where levels are separated by periods,
much like the Java or Python package namespace. So in the instance given
above, channel names might be "input" for the upper level, and "input.csv",
"input.xls" and "input.gnu" for the sub-levels. There is no arbitrary limit
to the depth of nesting.
\subsubsection{StreamHandler}
The logger is initialized with a \var{name} and an optional \var{level}.
The \class{StreamHandler} class sends logging output to streams such as
\var{sys.stdout}, \var{sys.stderr} or any file-like object (or, more
precisely, any object which supports \method{write()} and \method{flush()}
methods.
\begin{classdesc}{StreamHandler}{\optional{strm}}
Returns a new instance of the \class{StreamHandler} class. If \var{strm} is
specified, the instance will use it for logging output; otherwise,
\var{sys.stderr} will be used.
\end{classdesc}
\begin{methoddesc}{_log}{lvl, msg, args\optional{, exc_info=None}}
Low-level logging routine which creates a \class{LogRecord} and then calls
all the handlers of this logger to handle the record.
\end{methoddesc}
\begin{methoddesc}{addHandler}{hdlr}
Add the specified handler to this logger.
\end{methoddesc}
\begin{methoddesc}{callHandlers}{record}
Loop through all handlers for this logger and its parents in the logger
hierarchy. If no handler was found, output a one-off error message to
sys.stderr. Stop searching up the hierarchy whenever a logger with the
"propagate" attribute set to zero is found - that will be the last logger
whose handlers are called.
\end{methoddesc}
\begin{methoddesc}{critical}{msg, *args, **kwargs}
Log \code{msg \% args} with severity \code{CRITICAL}. To pass exception
information, use the keyword argument \var{exc_info} with a true value,
e.g., \code{logger.critical("Houston, we have a \%s", "major disaster",
exc_info=1)}.
\end{methoddesc}
\begin{methoddesc}{fatal}{msg, *args, **kwargs}
Synonym for \method{critical}.
\begin{methoddesc}{emit}{record}
If a formatter is specified, it is used to format the record.
The record is then written to the stream with a trailing newline.
If exception information is present, it is formatted using
\function{traceback.print_exception()} and appended to the stream.
\end{methoddesc}
\begin{methoddesc}{debug}{msg, *args, **kwargs}
Log \code{msg \% args} with severity \code{DEBUG}. To pass exception
information, use the keyword argument exc_info with a true value, e.g.,
\code{logger.debug("Houston, we have a \%s", "thorny problem", exc_info=1)}.
\begin{methoddesc}{flush}{}
Flushes the stream by calling its \method{flush()} method. Note that
the \method{close()} method is inherited from \class{Handler} and
so does nothing, so an explicit \method{flush()} call may be needed
at times.
\end{methoddesc}
\begin{methoddesc}{error}{msg, *args, **kwargs}
Log \code{msg \% args} with severity \code{ERROR}. To pass exception
information, use the keyword argument exc_info with a true value, e.g.,
\code{logger.error("Houston, we have a \%s", "major problem", exc_info=1)}
\subsubsection{FileHandler}
\end{methoddesc}
The \class{FileHandler} class sends logging output to a disk file.
It delegates the output functionality from \class{StreamHandler}.
\begin{methoddesc}{exception}{msg, *args}
Convenience method for logging an \code{ERROR} with exception information.
\begin{classdesc}{FileHandler}{filename\optional{, mode}}
Returns a new instance of the \class{FileHandler} class. The specified
file is opened and used as the stream for logging. If \var{mode} is
not specified, \constant{"a"} is used. By default, the file grows
indefinitely.
\end{classdesc}
\begin{methoddesc}{close}{}
Closes the file.
\end{methoddesc}
\begin{methoddesc}{emit}{record}
Outputs the record to the file.
\end{methoddesc}
\subsubsection{RotatingFileHandler}
The \class{RotatingFileHandler} class supports rotation of disk log files.
\begin{classdesc}{RotatingFileHandler}{filename\optional{, mode, maxBytes,
backupCount}}
Returns a new instance of the \class{RotatingFileHandler} class. The
specified file is opened and used as the stream for logging. If
\var{mode} is not specified, \constant{"a"} is used. By default, the
file grows indefinitely. You can use the \var{maxBytes} and
\var{backupCount} values to allow the file to \dfn{rollover} at a
predetermined size. When the size is about to be exceeded, the file is
closed and a new file opened for output, transparently to the
caller. Rollover occurs whenever the current log file is nearly
\var{maxBytes} in length. If \var{backupCount} is >= 1, the system
will successively create new files with the same pathname as the base
file, but with extensions ".1", ".2" etc. appended to it. For example,
with a backupCount of 5 and a base file name of "app.log", you would
get "app.log", "app.log.1", "app.log.2", ... through to
"app.log.5". When the last file reaches its size limit, the logging
reverts to "app.log" which is truncated to zero length. If
\var{maxBytes} is zero, rollover never occurs.
\end{classdesc}
\begin{methoddesc}{findCaller}{}
Find the stack frame of the caller so that we can note the source file name
and line number.
\begin{methoddesc}{doRollover}{}
Does a rollover, as described above.
\end{methoddesc}
\begin{methoddesc}{getEffectiveLevel}{}
Loop through this logger and its parents in the logger hierarchy, looking
for a non-zero logging level. Return the first one found.
\begin{methoddesc}{emit}{record}
Outputs the record to the file, catering for rollover as described
in \method{setRollover()}.
\end{methoddesc}
\begin{methoddesc}{handle}{record}
\subsubsection{SocketHandler}
Call the handlers for the specified \var{record}. This method is used for
unpickled records received from a socket, as well as those created
locally. Logger-level filtering is applied.
The \class{SocketHandler} class sends logging output to a network
socket. The base class uses a TCP socket.
\end{methoddesc}
\begin{methoddesc}{info}{msg, *args, **kwargs}
Log \code{msg \% args} with severity \code{INFO}. To pass exception
information, use the keyword argument exc_info with a true value, e.g.,
\code{logger.info("Houston, we have a \%s", "interesting problem",
exc_info=1)}
\begin{classdesc}{SocketHandler}{host, port}
Returns a new instance of the \class{SocketHandler} class intended to
communicate with a remote machine whose address is given by \var{host}
and \var{port}.
\end{classdesc}
\begin{methoddesc}{close}{}
Closes the socket.
\end{methoddesc}
\begin{methoddesc}{isEnabledFor}{lvl}
Is this logger enabled for level \var{lvl}?
\begin{methoddesc}{handleError}{}
\end{methoddesc}
\begin{methoddesc}{log}{lvl, msg, *args, **kwargs}
Log \code{msg \% args} with the severity \var{lvl}. To pass exception
information, use the keyword argument \var{exc_info} with a true value,
e.g., \code{logger.log(lvl, "We have a \%s", "mysterious problem",
exc_info=1)}
\begin{methoddesc}{emit}{}
Pickles the record and writes it to the socket in binary format.
If there is an error with the socket, silently drops the packet.
If the connection was previously lost, re-establishes the connection.
\end{methoddesc}
\begin{methoddesc}{makeRecord}{name, lvl, fn, lno, msg, args, exc_info}
A factory method which can be overridden in subclasses to create specialized
\code{LogRecord} instances.
\begin{methoddesc}{handleError}{}
Handles an error which has occurred during \method{emit()}. The
most likely cause is a lost connection. Closes the socket so that
we can retry on the next event.
\end{methoddesc}
\begin{methoddesc}{removeHandler}{hdlr}
Remove the specified handler from this logger.
\begin{methoddesc}{makeSocket}{}
This is a factory method which allows subclasses to define the precise
type of socket they want. The default implementation creates a TCP
socket (\constant{socket.SOCK_STREAM}).
\end{methoddesc}
\begin{methoddesc}{setLevel}{level}
Set the logging \var{level} of this logger.
\begin{methoddesc}{makePickle}{record}
Pickles the record in binary format with a length prefix, and returns
it ready for transmission across the socket.
\end{methoddesc}
\begin{methoddesc}{warn}{msg, *args, **kwargs}
Log \code{msg \% args} with severity \code{WARN}. To pass exception
information, use the keyword argument exc_info with a true value, e.g.,
\code{logger.warn("Houston, we have a \%s", "bit of a problem", exc_info=1)}
\begin{methoddesc}{send}{packet}
Send a pickled string \var{packe} to the socket. This function allows
for partial sends which can happen when the network is busy.
\end{methoddesc}
\subsubsection{DatagramHandler}
\begin{classdesc}{Manager}{root}
There is (under normal circumstances) just one \code{Manager} instance,
which holds the hierarchy of loggers.
The manager is initialized with the \var{root} node of the logger hierarchy.
The \class{DatagramHandler} class inherits from \class{SocketHandler}
to support sending logging messages over UDP sockets.
\begin{classdesc}{DatagramHandler}{host, port}
Returns a new instance of the \class{DatagramHandler} class intended to
communicate with a remote machine whose address is given by \var{host}
and \var{port}.
\end{classdesc}
\begin{methoddesc}{_fixupChildren}{ph, logger}
Ensure that children of the placeholder \var{ph} are connected to the
specified \code{logger}.
\begin{methoddesc}{emit}{}
Pickles the record and writes it to the socket in binary format.
If there is an error with the socket, silently drops the packet.
\end{methoddesc}
\begin{methoddesc}{_fixupParents}{logger}
Ensure that there are either loggers or placeholders all the way from the
specified \var{logger} to the root of the logger hierarchy.
\begin{methoddesc}{makeSocket}{}
The factory method of \class{SocketHandler} is here overridden to create
a UDP socket (\constant{socket.SOCK_DGRAM}).
\end{methoddesc}
\begin{methoddesc}{getLogger}{name}
Get a logger with the specified \var{name} (channel name), creating it if it
doesn't yet exist. If a PlaceHolder existed for the specified name (i.e. the
logger didn't exist but a child of it did), replace it with the created
logger and fix up the parent/child references which pointed to the
placeholder to now point to the logger.
\begin{methoddesc}{send}{s}
Send a pickled string to a socket. This function allows for
partial sends which can happen when the network is busy.
\end{methoddesc}
\begin{classdesc}{MemoryHandler}{capacity\optional{,
flushLevel=40\optional{, target=None}}}
\subsubsection{SysLogHandler}
A handler class which buffers logging records in memory, periodically
flushing them to a target handler. Flushing occurs whenever the buffer is
full, or when an event of a certain severity or greater is seen.
The handler is initialized with the buffer size (\var{capacity}), the level
at which flushing should occur (\var{flushLevel}) and an optional
{}\var{target}. Note that without a target being set either here or via
\code{setTarget()}, a \class{MemoryHandler} is no use to anyone!
The \class{SysLogHandler} class supports sending logging messages to a
remote or local Unix syslog.
\begin{classdesc}{SysLogHandler}{\optional{address\optional{, facility}}}
Returns a new instance of the \class{SysLogHandler} class intended to
communicate with a remote Unix machine whose address is given by
\var{address} in the form of a (host, port) tuple. If \var{address} is not
specified, ('localhost', 514) is used. The address is used to open a UDP
socket. If \var{facility} is not specified, \constant{LOG_USER} is used.
\end{classdesc}
\begin{methoddesc}{close}{}
Flush, set the target to None and lose the buffer.
\end{methoddesc}
\begin{methoddesc}{flush}{}
For a \class{MemoryHandler}, flushing means just sending the buffered
records to the target, if there is one. Override if you want different
behavior.
Closes the socket to the remote host.
\end{methoddesc}
\begin{methoddesc}{setTarget}{target}
Set the \var{target} handler for this handler.
\end{methoddesc}
\begin{methoddesc}{shouldFlush}{record}
Check for buffer full or a \var{record} at the flushLevel or higher.
\begin{methoddesc}{emit}{record}
The record is formatted, and then sent to the syslog server. If
exception information is present, it is \emph{not} sent to the server.
\end{methoddesc}
\begin{classdesc}{NTEventLogHandler}{appname\optional{,
dllname=None\optional{, logtype='Application'}}}
A handler class which sends events to the NT Event Log. Adds a registry
entry for the specified application name. If no \var{dllname} is provided,
\code{win32service.pyd} (which contains some basic message placeholders) is
used. Note that use of these placeholders will make your event logs big, as
the entire message source is held in the log. If you want slimmer logs, you
have to pass in the name of your own DLL which contains the message
definitions you want to use in the event log.
XXX what is \var{logtype}?
\begin{methoddesc}{encodePriority}{facility, priority}
Encodes the facility and priority into an integer. You can pass in strings
or integers - if strings are passed, internal mapping dictionaries are used
to convert them to integers.
\end{methoddesc}
\subsubsection{NTEventLogHandler}
The \class{NTEventLogHandler} class supports sending logging messages
to a local Windows NT, Windows 2000 or Windows XP event log. Before
you can use it, you need Mark Hammond's Win32 extensions for Python
installed.
\begin{classdesc}{NTEventLogHandler}{appname
\optional{, dllname\optional{, logtype}}}
Returns a new instance of the \class{NTEventLogHandler} class. The
\var{appname} is used to define the application name as it appears in the
event log. An appropriate registry entry is created using this name.
The \var{dllname} should give the fully qualified pathname of a .dll or .exe
which contains message definitions to hold in the log (if not specified,
\constant{"win32service.pyd"} is used - this is installed with the Win32
extensions and contains some basic placeholder message definitions.
Note that use of these placeholders will make your event logs big, as the
entire message source is held in the log. If you want slimmer logs, you have
to pass in the name of your own .dll or .exe which contains the message
definitions you want to use in the event log). The \var{logtype} is one of
\constant{"Application"}, \constant{"System"} or \constant{"Security"}, and
defaults to \constant{"Application"}.
\end{classdesc}
\begin{methoddesc}{close}{}
You can remove the application name from the registry as a source of event
log entries. However, if you do this, you will not be able to see the events
as you intended in the Event Log Viewer - it needs to be able to access the
registry to get the DLL name.
At this point, you can remove the application name from the registry as a
source of event log entries. However, if you do this, you will not be able
to see the events as you intended in the Event Log Viewer - it needs to be
able to access the registry to get the .dll name. The current version does
not do this (in fact it doesn't do anything).
\end{methoddesc}
\begin{methoddesc}{emit}{record}
Determine the message ID, event category and event type. Then log the
\var{record} in the NT event log.
Determines the message ID, event category and event type, and then logs the
message in the NT event log.
\end{methoddesc}
\begin{methoddesc}{getEventCategory}{record}
Return the event category for the \var{record}. Override this if you want
to specify your own categories. This version returns 0.
Returns the event category for the record. Override this if you
want to specify your own categories. This version returns 0.
\end{methoddesc}
\begin{methoddesc}{getEventType}{record}
Return the event type for the \var{record}. Override this if you want to
specify your own types. This version does a mapping using the handler's
typemap attribute, which is set up in the constructor to a dictionary which
contains mappings for \var{DEBUG}, \var{INFO}, \var{WARN}, \var{ERROR} and
{}\var{CRITICAL}. If you are using your own levels you will either need to
override this method or place a suitable dictionary in the handler's typemap
attribute.
Returns the event type for the record. Override this if you want
to specify your own types. This version does a mapping using the
handler's typemap attribute, which is set up in \method{__init__()}
to a dictionary which contains mappings for \constant{DEBUG},
\constant{INFO}, \constant{WARNING}, \constant{ERROR} and
\constant{CRITICAL}. If you are using your own levels, you will either need
to override this method or place a suitable dictionary in the
handler's \var{typemap} attribute.
\end{methoddesc}
\begin{methoddesc}{getMessageID}{record}
Return the message ID for the event \var{record}. If you are using your own
messages, you could do this by having the msg passed to the logger being an
ID rather than a formatting string. Then, in here, you could use a
dictionary lookup to get the message ID. This version returns 1, which is
the base message ID in \code{win32service.pyd}.
Returns the message ID for the record. If you are using your
own messages, you could do this by having the \var{msg} passed to the
logger being an ID rather than a format string. Then, in here,
you could use a dictionary lookup to get the message ID. This
version returns 1, which is the base message ID in
\constant{win32service.pyd}.
\end{methoddesc}
\subsubsection{SMTPHandler}
\begin{classdesc}{PlaceHolder}{logger}
The \class{SMTPHandler} class supports sending logging messages to an email
address via SMTP.
\class{PlaceHolder} instances are used in the \class{Manager} logger
hierarchy to take the place of nodes for which no loggers have been defined
Initialize with the specified \var{logger} being a child of this
\class{PlaceHolder}.
\end{classdesc}
\begin{methoddesc}{append}{logger}
Add the specified \var{logger} as a child of this placeholder.
\end{methoddesc}
\begin{classdesc}{RootLogger}{level}
A root logger is not that different to any other logger, except that it must
have a logging \var{level} and there is only one instance of it in the
hierarchy.
\end{classdesc}
\begin{classdesc}{SMTPHandler}{mailhost, fromaddr, toaddr, subject}
A handler class which sends an SMTP email for each logging event.
The instance is initialized with the from (\var{fromaddr}) and to
(\var{toaddr}) addresses and \var{subject} line of the email. To specify a
\begin{classdesc}{SMTPHandler}{mailhost, fromaddr, toaddrs, subject}
Returns a new instance of the \class{SMTPHandler} class. The
instance is initialized with the from and to addresses and subject
line of the email. The \var{toaddrs} should be a list of strings without
domain names (That's what the \var{mailhost} is for). To specify a
non-standard SMTP port, use the (host, port) tuple format for the
\var{mailhost} argument.
\var{mailhost} argument. If you use a string, the standard SMTP port
is used.
\end{classdesc}
\begin{methoddesc}{emit}{record}
Format the \var{record} and send it to the specified addressees.
Formats the record and sends it to the specified addressees.
\end{methoddesc}
\begin{methoddesc}{getSubject}{record}
If you want to specify a subject line which is \var{record}-dependent,
If you want to specify a subject line which is record-dependent,
override this method.
\end{methoddesc}
\begin{classdesc}{SocketHandler}{host, port}
\subsubsection{MemoryHandler}
A handler class which writes pickled logging records to a streaming
socket. The socket is kept open across logging calls. If the peer resets
it, an attempt is made to reconnect on the next call. Note that the very
simple wire protocol used means that packet sizes are expected to be
encodable within 16 bits (i.e. < 32767 bytes).
The \class{MemoryHandler} supports buffering of logging records in memory,
periodically flushing them to a \dfn{target} handler. Flushing occurs
whenever the buffer is full, or when an event of a certain severity or
greater is seen.
The handler is initialized with a specific \var{host} address and
{}\var{port}. The attribute \var{closeOnError} is set to 1 - which means
that if a socket error occurs, the socket is silently closed and then
reopened on the next logging call.
\class{MemoryHandler} is a subclass of the more general
\class{BufferingHandler}, which is an abstract class. This buffers logging
records in memory. Whenever each record is added to the buffer, a
check is made by calling \method{shouldFlush()} to see if the buffer
should be flushed. If it should, then \method{flush()} is expected to
do the needful.
\begin{classdesc}{BufferingHandler}{capacity}
Initializes the handler with a buffer of the specified capacity.
\end{classdesc}
\begin{methoddesc}{close}{}
Closes the socket.
\end{methoddesc}
\begin{methoddesc}{emit}{record}
Pickles the \var{record} and writes it to the socket in binary format. If
there is an error with the socket, silently drop the packet. If there was a
problem with the socket, re-establishes the socket.
\end{methoddesc}
\begin{methoddesc}{handleError}{}
An error has occurred during logging. Most likely cause - connection lost.
Close the socket so that we can retry on the next event.
Appends the record to the buffer. If \method{shouldFlush()} returns true,
calls \method{flush()} to process the buffer.
\end{methoddesc}
\begin{methoddesc}{makePickle}{record}
Pickles the \var{record} in binary format with a length prefix, and returns
it ready for transmission across the socket.
\end{methoddesc}
\begin{methoddesc}{makeSocket}{}
A factory method which allows subclasses to define the precise type of
socket they want.
\begin{methoddesc}{flush}{}
You can override this to implement custom flushing behaviour. This version
just zaps the buffer to empty.
\end{methoddesc}
\begin{methoddesc}{send}{s}
Send a pickled string (\var{s}) to the socket. This function allows for
partial sends which can happen when the network is busy.
\begin{methoddesc}{shouldFlush}{record}
Returns true if the buffer is up to capacity. This method can be
overridden to implement custom flushing strategies.
\end{methoddesc}
\begin{classdesc}{StreamHandler}{\optional{strm=None}}
A handler class which writes logging records, appropriately formatted, to a
stream. Note that this class does not close the stream, as \var{sys.stdout}
or \var{sys.stderr} may be used.
If \var{strm} is not specified, \var{sys.stderr} is used.
\begin{classdesc}{MemoryHandler}{capacity\optional{, flushLevel
\optional{, target}}}
Returns a new instance of the \class{MemoryHandler} class. The
instance is initialized with a buffer size of \var{capacity}. If
\var{flushLevel} is not specified, \constant{ERROR} is used. If no
\var{target} is specified, the target will need to be set using
\method{setTarget()} before this handler does anything useful.
\end{classdesc}
\begin{methoddesc}{emit}{record}
If a formatter is specified, it is used to format the \var{record}. The
record is then written to the stream with a trailing newline (N.B. this may
be removed depending on feedback). If exception information is present, it
is formatted using \var{traceback.print_exception} and appended to the
stream.
\begin{methoddesc}{close}{}
Calls \method{flush()}, sets the target to \constant{None} and
clears the buffer.
\end{methoddesc}
\begin{methoddesc}{flush}{}
For a \class{MemoryHandler}, flushing means just sending the buffered
records to the target, if there is one. Override if you want
different behaviour.
\end{methoddesc}
Flushes the stream.
\begin{methoddesc}{setTarget}{target}
Sets the target handler for this handler.
\end{methoddesc}
\begin{methoddesc}{shouldFlush}{record}
Checks for buffer full or a record at the \var{flushLevel} or higher.
\end{methoddesc}
\begin{classdesc}{SysLogHandler}{\optional{address=('localhost',
514)\optional{, facility=1}}}
\subsubsection{HTTPHandler}
A handler class which sends formatted logging records to a syslog
server. Based on Sam Rushing's
\ulink{http://www.nightmare.com/squirl/python-ext/misc/syslog.py}{syslog
module}. Contributed by Nicolas Untz (after which minor refactoring changes
have been made).
The \class{HTTPHandler} class supports sending logging messages to a
Web server, using either GET or POST semantics.
If \var{address} is specified as a string, UNIX socket is used. If
\var{facility} is not specified, \code{LOG_USER} is used.
\begin{classdesc}{HTTPHandler}{host, url\optional{, method}}
Returns a new instance of the \class{HTTPHandler} class. The
instance is initialized with a host address, url and HTTP method.
If no \var{method} is specified, GET is used.
\end{classdesc}
\begin{methoddesc}{emit}{record}
Sends the record to the Web server as an URL-encoded dictionary.
\end{methoddesc}
\subsection{Formatter Objects}
\class{Formatter}s have the following attributes and methods. They are
responsible for converting a \class{LogRecord} to (usually) a string
which can be interpreted by either a human or an external system. The
base
\class{Formatter} allows a formatting string to be specified. If none is
supplied, the default value of "\%s(message)\\n" is used.
A Formatter can be initialized with a format string which makes use of
knowledge of the \class{LogRecord} attributes - e.g. the default value
mentioned above makes use of the fact that the user's message and
arguments are pre- formatted into a LogRecord's \var{message}
attribute. Currently, the useful attributes in a LogRecord are
described by:
\%(name)s Name of the logger (logging channel)
\%(levelno)s Numeric logging level for the message (DEBUG, INFO,
WARNING, ERROR, CRITICAL)
\%(levelname)s Text logging level for the message ("DEBUG", "INFO",
"WARNING", "ERROR", "CRITICAL")
\%(pathname)s Full pathname of the source file where the logging
call was issued (if available)
\%(filename)s Filename portion of pathname
\%(module)s Module (name portion of filename)
\%(lineno)d Source line number where the logging call was issued
(if available)
\%(created)f Time when the LogRecord was created (time.time()
return value)
\%(asctime)s Textual time when the LogRecord was created
\%(msecs)d Millisecond portion of the creation time
\%(relativeCreated)d Time in milliseconds when the LogRecord was created,
relative to the time the logging module was loaded
(typically at application startup time)
\%(thread)d Thread ID (if available)
\%(message)s The result of msg \% args, computed just as the
record is emitted
\begin{classdesc}{Formatter}{\optional{fmt\optional{, datefmt}}}
Returns a new instance of the \class{Formatter} class. The
instance is initialized with a format string for the message as a whole,
as well as a format string for the date/time portion of a message. If
no \var{fmt} is specified, "\%(message)s" is used. If no \var{datefmt}
is specified, the ISO8601 date format is used.
\end{classdesc}
\begin{methoddesc}{close}{}
\begin{methoddesc}{format}{record}
The record's attribute dictionary is used as the operand to a
string formatting operation. Returns the resulting string.
Before formatting the dictionary, a couple of preparatory steps
are carried out. The \var{message} attribute of the record is computed
using \var{msg} \% \var{args}. If the formatting string contains
\constant{"(asctime)"}, \method{formatTime()} is called to format the
event time. If there is exception information, it is formatted using
\method{formatException()} and appended to the message.
\end{methoddesc}
\begin{methoddesc}{formatTime}{record\optional{, datefmt}}
This method should be called from \method{format()} by a formatter which
wants to make use of a formatted time. This method can be overridden
in formatters to provide for any specific requirement, but the
basic behaviour is as follows: if \var{datefmt} (a string) is specified,
it is used with \method{time.strftime()} to format the creation time of the
record. Otherwise, the ISO8601 format is used. The resulting
string is returned.
\end{methoddesc}
\begin{methoddesc}{formatException}{exc_info}
Formats the specified exception information (a standard exception tuple
as returned by \method{sys.exc_info()}) as a string. This default
implementation just uses \method{traceback.print_exception()}.
The resulting string is returned.
\end{methoddesc}
\subsection{Filter Objects}
\class{Filter}s can be used by \class{Handler}s and \class{Logger}s for
more sophisticated filtering than is provided by levels. The base filter
class only allows events which are below a certain point in the logger
hierarchy. For example, a filter initialized with "A.B" will allow events
logged by loggers "A.B", "A.B.C", "A.B.C.D", "A.B.D" etc. but not "A.BB",
"B.A.B" etc. If initialized with the empty string, all events are passed.
\begin{classdesc}{Filter}{\optional{name}}
Returns an instance of the \class{Filter} class. If \var{name} is specified,
it names a logger which, together with its children, will have its events
allowed through the filter. If no name is specified, allows every event.
\end{classdesc}
Closes the socket.
\begin{methoddesc}{filter}{record}
Is the specified record to be logged? Returns zero for no, nonzero for
yes. If deemed appropriate, the record may be modified in-place by this
method.
\end{methoddesc}
\subsection{LogRecord Objects}
LogRecord instances are created every time something is logged. They
contain all the information pertinent to the event being logged. The
main information passed in is in msg and args, which are combined
using msg \% args to create the message field of the record. The record
also includes information such as when the record was created, the
source line where the logging call was made, and any exception
information to be logged.
LogRecord has no methods; it's just a repository for information about the
logging event. The only reason it's a class rather than a dictionary is to
facilitate extension.
\begin{classdesc}{LogRecord}{name, lvl, pathname, lineno, msg, args,
exc_info}
Returns an instance of \class{LogRecord} initialized with interesting
information. The \var{name} is the logger name; \var{lvl} is the
numeric level; \var{pathname} is the absolute pathname of the source
file in which the logging call was made; \var{lineno} is the line
number in that file where the logging call is found; \var{msg} is the
user-supplied message (a format string); \var{args} is the tuple
which, together with \var{msg}, makes up the user message; and
\var{exc_info} is the exception tuple obtained by calling
\function{sys.exc_info() }(or \constant{None}, if no exception information
is available).
\end{classdesc}
\end{methoddesc}
\subsection{Thread Safety}
\begin{methoddesc}{emit}{record}
The logging module is intended to be thread-safe without any special work
needing to be done by its clients. It achieves this though using threading
locks; there is one lock to serialize access to the module's shared data,
and each handler also creates a lock to serialize access to its underlying
I/O.
The \var{record} is formatted, and then sent to the syslog server. If
exception information is present, it is not sent to the server.
\subsection{Configuration}
\end{methoddesc}
\begin{methoddesc}{encodePriority}{facility, priority}
\subsubsection{Configuration functions}
Encode the \var{facility} and \var{priority}. You can pass in strings or
integers - if strings are passed, the \var{facility_names} and
\var{priority_names} mapping dictionaries are used to convert them to
integers.
The following functions allow the logging module to be configured.
\end{methoddesc}
\begin{funcdesc}{fileConfig}{fname\optional{, defaults}}
Reads the logging configuration from a ConfigParser-format file named
\var{fname}. This function can be called several times from an application,
allowing an end user the ability to select from various pre-canned
configurations (if the developer provides a mechanism to present the
choices and load the chosen configuration). Defaults to be passed to
ConfigParser can be specified in the \var{defaults} argument.
\end{funcdesc}
\begin{funcdesc}{listen}{\optional{port}}
Starts up a socket server on the specified port, and listens for new
configurations. If no port is specified, the module's default
\constant{DEFAULT_LOGGING_CONFIG_PORT} is used. Logging configurations
will be sent as a file suitable for processing by \function{fileConfig()}.
Returns a \class{Thread} instance on which you can call \method{start()}
to start the server, and which you can \method{join()} when appropriate.
To stop the server, call \function{stopListening()}.
\end{funcdesc}
\subsection{Examples \label{logging-example}}
\begin{funcdesc}{stopListening}{}
Stops the listening server which was created with a call to
\function{listen()}. This is typically called before calling \method{join()}
on the return value from \function{listen()}.
\end{funcdesc}
Using the package doesn't get much simpler. It is packaged as a Python
package. You just need to \code{import logging} and you're ready to
go. Minimal example:
\subsubsection{Configuration file format}
The configuration file format understood by \function{fileConfig} is
based on ConfigParser functionality. The file must contain sections
called \code{[loggers]}, \code{[handlers]} and \code{[formatters]}
which identify by name the entities of each type which are defined in
the file. For each such entity, there is a separate section which
identified how that entity is configured. Thus, for a logger named
\code{log01} in the \code{[loggers]} section, the relevant
configuration details are held in a section
\code{[logger_log01]}. Similarly, a handler called \code{hand01} in
the \code{[handlers]} section will have its configuration held in a
section called \code{[handler_hand01]}, while a formatter called
\code{form01} in the \code{[formatters]} section will have its
configuration specified in a section called
\code{[formatter_form01]}. The root logger configuration must be
specified in a section called \code{[logger_root]}.
Examples of these sections in the file are given below.
\begin{verbatim}
# -- app.py --
import logging
[loggers]
keys=root,log02,log03,log04,log05,log06,log07
logging.info("Starting...")
logging.warn("Nothing to do!")
logging.info("Done...")
[handlers]
keys=hand01,hand02,hand03,hand04,hand05,hand06,hand07,hand08,hand09
[formatters]
keys=form01,form02,form03,form04,form05,form06,form07,form08,form09
\end{verbatim}
When you run \code{app.py}, the results are:
The root logger must specify a level and a list of handlers. An
example of a root logger section is given below.
\begin{verbatim}
2002-03-15 01:09:10,440 root INFO - Starting...
2002-03-15 01:09:10,440 root WARN - Nothing to do!
2002-03-15 01:09:10,440 root INFO - Done...
[logger_root]
level=NOTSET
handlers=hand01
\end{verbatim}
The \code{level} entry can be one of \code{DEBUG, INFO, WARNING,
ERROR, CRITICAL} or \code{NOTSET}. For the root logger only,
\code{NOTSET} means that all messages will be logged. Level values are
\function{eval()}uated in the context of the \code{logging} package's
namespace.
The \code{handlers} entry is a comma-separated list of handler names,
which must appear in the \code{[handlers]} section. These names must
appear in the \code{[handlers]} section and have corresponding
sections in the configuration file.
Here's a
slightly more involved example; if you've just looked at \pep{282} you will
probably get a feeling of dejà vu. (This is intentional.)
For loggers other than the root logger, some additional information is
required. This is illustrated by the following example.
\begin{verbatim}
# -- mymodule.py --
import logging
log = logging.getLogger("MyModule")
def doIt():
log.debug("doin' stuff")
#do stuff...but suppose an error occurs?
raise TypeError, "bogus type error for testing"
[logger_parser]
level=DEBUG
handlers=hand01
propagate=1
qualname=compiler.parser
\end{verbatim}
The \code{level} and \code{handlers} entries are interpreted as for
the root logger, except that if a non-root logger's level is specified
as \code{NOTSET}, the system consults loggers higher up the hierarchy
to determine the effective level of the logger. The \code{propagate}
entry is set to 1 to indicate that messages must propagate to handlers
higher up the logger hierarchy from this logger, or 0 to indicate that
messages are \strong{not} propagated to handlers up the hierarchy. The
\code{qualname} entry is the hierarchical channel name of the logger,
i.e. the name used by the application to get the logger.
Sections which specify handler configuration are exemplified by the
following.
\begin{verbatim}
# -- myapp.py --
import logging, mymodule
[handler_hand01]
class=StreamHandler
level=NOTSET
formatter=form01
args=(sys.stdout,)
\end{verbatim}
logging.basicConfig() # basic configuration - console output
The \code{class} entry indicates the handler's class (as determined by
\function{eval()} in the \code{logging} package's namespace). The
\code{level} is interpreted as for loggers, and \code{NOTSET} is taken
to mean "log everything".
log = logging.getLogger("MyApp")
The \code{formatter} entry indicates the key name of the formatter for
this handler. If blank, a default formatter
(\code{logging._defaultFormatter}) is used. If a name is specified, it
must appear in the \code{[formatters]} section and have a
corresponding section in the configuration file.
log.info("start my app")
try:
mymodule.doIt()
except Exception, e:
log.exception("There was a problem doin' stuff.")
log.info("end my app")
The \code{args} entry, when \function{eval()}uated in the context of
the \code{logging} package's namespace, is the list of arguments to
the constructor for the handler class. Refer to the constructors for
the relevant handlers, or to the examples below, to see how typical
entries are constructed.
\begin{verbatim}
[handler_hand02]
class=FileHandler
level=DEBUG
formatter=form02
args=('python.log', 'w')
[handler_hand03]
class=handlers.SocketHandler
level=INFO
formatter=form03
args=('localhost', handlers.DEFAULT_TCP_LOGGING_PORT)
[handler_hand04]
class=handlers.DatagramHandler
level=WARN
formatter=form04
args=('localhost', handlers.DEFAULT_UDP_LOGGING_PORT)
[handler_hand05]
class=handlers.SysLogHandler
level=ERROR
formatter=form05
args=(('localhost', handlers.SYSLOG_UDP_PORT), handlers.SysLogHandler.LOG_USER)
[handler_hand06]
class=NTEventLogHandler
level=CRITICAL
formatter=form06
args=('Python Application', '', 'Application')
[handler_hand07]
class=SMTPHandler
level=WARN
formatter=form07
args=('localhost', 'from@abc', ['user1@abc', 'user2@xyz'], 'Logger Subject')
[handler_hand08]
class=MemoryHandler
level=NOTSET
formatter=form08
target=
args=(10, ERROR)
[handler_hand09]
class=HTTPHandler
level=NOTSET
formatter=form09
args=('localhost:9022', '/log', 'GET')
\end{verbatim}
When you run \code{myapp.py}, the results are:
Sections which specify formatter configuration are typified by the following.
\begin{verbatim}
2002-03-14 23:40:49,299 MyApp INFO - start my app
2002-03-14 23:40:49,299 MyModule DEBUG - doin' stuff
2002-03-14 23:40:49,299 MyApp ERROR - There was a problem doin' stuff.
Traceback (innermost last):
File "myapp.py", line 9, in ?
mymodule.doIt()
File "mymodule.py", line 7, in doIt
raise TypeError, "bogus type error for testing"
TypeError: bogus type error for testing
2002-03-14 23:40:49,409 MyApp INFO - end my app
[formatter_form01]
format=F1 %(asctime)s %(levelname)s %(message)s
datefmt=
\end{verbatim}
The \code{format} entry is the overall format string, and the
\code{datefmt} entry is the \function{strftime()}-compatible date/time format
string. If empty, the package substitutes ISO8601 format date/times, which
is almost equivalent to specifying the date format string "%Y-%m-%d %H:%M:%S".
The ISO8601 format also specifies milliseconds, which are appended to the
result of using the above format string, with a comma separator. An example
time in ISO8601 format is \code{2003-01-23 00:29:50,411}.
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