Viewing file:  logger.py (23.77 KB) -rw-r--r--
Select action/file-type:
 (+) |  (+) |  (+) | Code (+) | Session (+) |  (+) | SDB (+) |  (+) |  (+) |  (+) |  (+) |  (+) |
"""
A module for convenient yet powerful file, console, and syslog logging
BASIC USAGE
from logger import Logger
log = Logger(threshold=0) # create the log object and give it
# a threshold of 0
log.log(2, 'all done') # send a log of priority 2 (not printed)
log(0, 'error: bandits!') # send a log of priority 0 (printed)
log.write(0, stringvar) # do a raw write on the file object
DESCRIPTION
Each logging object is given a threshold. Any messages that are
then sent to that object are logged only if their priority meets or
exceeds the threshold. Lower numerical priority means that a
message is more important. For example: if a log object has
threshold 2, then all messages of priority 2, 1, 0, -1, etc will be
logged, while those of priority 3, 4, etc. will not. I suggest the
following scale:
LOG PRIORITY MEANING
-1 failure - cannot be ignored
0 important message - printed in default mode
1 informational message - printed with -v
2 debugging information
THRESHOLD MEANING
-1 quiet mode (-q) only failures are printed
0 normal operation
1 verbose mode (-v)
2 debug mode (-vv or -d)
It can be extended farther in both directions, but that is rarely
useful. It can also be shifted in either direction. This might be
useful if you want to supply the threshold directly on the command
line but have trouble passing in negative numbers. In that case,
add 1 to all thresholds and priorities listed above.
CLASSES
There are three primary classes defined in this module:
Logger Class for basic file and console logging
SysLogger Class for syslog logging
LogContainer Class for wrapping multiple other loggers together
for convenient use
Instances of all of these support the same basic methods:
obj.log(priority, message) # log a message with smart formatting
obj.write(priority, message) # log a string in a ver raw way
obj(priority, message) # shorthand for obj.log(...)
Different classes support other methods as well, but this is what you
will mostly use.
ADVANCED
There are a number of options available for these classes. These are
documented below in the respective classes and methods. Here is a
list of some of the things you can do:
* make a prefix contain a string which gets repeated for more
important logs. (prefix)
* directly test if a log object WOULD log, so you can do
complicated stuff, like efficient for loops. (test)
* make the priority, threshold arbitrary objects, with a
home-rolled test to see if it should log. (test)
* give log containers a "master threshold" and define arbitrary
behavior based on it. Examples include:
- only pass on messages of sufficient priority (ragardless of
the thresholds of the log ojects).
- only pass on messages to objects whose thresholds are
(numerically) lower than the master threshold.
SEE ALSO
Take a look at the examples at the end of this file in the test &
demo section.
COMMENTS
I welcome comments, questions, bug reports and requests... I'm very
lonely. :)
"""
# 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 2 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 Library General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
# Copyright 2001-2003 Michael D. Stenner
import sys
import string
# syslog is imported from within SysLogger.__init__
AUTHOR = "Michael D. Stenner <mstenner@phy.duke.edu>"
VERSION = "0.7"
DATE = "2003/09/20"
URL = "http://linux.duke.edu/projects/mini/logger/"
class Logger:
"""A class for file-object logging
USAGE:
from logger import Logger
log_obj = Logger(THRESHOLD) # create the instance
log_obj.log(3, 'message') # log a message with priority 3
log_obj(3, 'message') # same thing
log_obj(3, ['message']) # same thing
log_obj.test(3) # boolean - would a message of
# this priority be printed?
# a raw write call after the priority test, for writing
# arbitrary text -- (this will not be followed by \\n)
log_obj.write(3, 'thing\\nto\\nwrite')
# generate the prefix used for priority 3
pr = log_obj.gen_prefix(3)
# see the examples in the test section for more
BASIC OPTIONS:
There are a couple of basic options that are commonly needed.
These are attribues of instances of class Logger.
preprefix
Text that will be printed at the start of each line of
output (for log()ged, not write()en messages). This might
be your program's name, for example.
log.preprefix = 'myprog'
If preprefix is callable, then it will be called for each
log and the returned value will be used. This is useful for
printing the current time.
import time
def printtime():
return time.strftime('%m/%d/%y %H:%M:%S ',
time.localtime(time.time()))
log.preprefix = printtime
file_object
This is the file object to which output is directed. If it
is None, then the logs are quietly dropped.
There are other options described in the next section, but these
are the most commonly used.
ATTRIBUTES:
(all of these are settable as keyword args to __init__)
ATTRIBUTES DEFAULT DESCRIPTION
----------------------------------------------------------
threshold = 0 how verbose the program should be
file_object = sys.stderr file object to which output goes
prefix = '' prefix string - repeated for more
important logs
prefix_depth = 5 times prefix is repeated for logs
of priority 0. Basically, set this
one larger than your highest log
priority.
preprefix = '' string printed before the prefix
if callable, returned string will
be used (useful for printing time)
postprefix = '' string printed after the prefix
default = 1 default priority to log at
"""
def __init__(self,
threshold = 0,
file_object = sys.stderr,
prefix = '',
prefix_depth = 5,
preprefix = '',
postprefix = '',
default = 1):
self.threshold = threshold
self.file_object = file_object
self.prefix = prefix
self.prefix_depth = prefix_depth
self.preprefix = preprefix
self.postprefix = postprefix
self.default = default
def test(self, priority):
"""
Return true if a log of the given priority would be printed.
This can be overridden to do any test you like. Specifically,
priority and threshold need not be integers. They can be
arbitrary objects. You need only override this method, and
possibly gen_prefix.
"""
return int(self.threshold) >= int(priority)
def gen_prefix(self, priority):
"""
Return the full prefix (including pre and post) for the
given priority.
If you use prefix and use a more complicated priority and
verbosity (non-numerical), then you should either give the
chosen object a __int__ method, or override this function.
"""
if callable(self.preprefix): prefix = self.preprefix()
else: prefix = self.preprefix
if self.prefix:
depth = self.prefix_depth - int(priority)
if depth < 1: depth = 1
for i in range(0, depth):
prefix = prefix + self.prefix
return prefix + self.postprefix
def log(self, priority, message=None):
"""
Print a log message. This prepends the prefix to each line
and does some basic formatting.
"""
p, m = self._use_default(priority, message)
if self.test(p):
if self.file_object is None: return
if type(m) == type(''): # message is a string
mlist = string.split(m, '\n')
if mlist[-1] == '': del mlist[-1] # string ends in \n
elif type(m) == type([]): # message is a list
mlist = map(string.rstrip, m)
else: mlist = [str(m)] # message is other type
prefix = self.gen_prefix(p)
for line in mlist:
self.file_object.write(prefix + line + '\n')
# make the objects callable
__call__ = log
def write(self, priority, message=None):
"""
Print a log message. In this case, 'message' must be a string
as it will be passed directly to the file object's write method.
"""
p, m = self._use_default(priority, message)
if self.test(p):
if self.file_object is None: return
self.file_object.write(m)
def _use_default(self, priority, message):
"""Substitute default priority if none was provided"""
if message == None: return self.default, priority
else: return priority, message
class SysLogger:
"""A class for file-object logging
USAGE:
For the most part, SysLogger instances are used just like Logger
instances. Notable exceptions:
* prefixes aren't used (at least not as they are for Logger)
* map_priority is pretty important because it controls
conversion between Logger priorities and syslog priorities
* although priority/threshold/test works the same, there is
also maskpri and your syslog config which will limit what
gets logged. Keep this in mind if you see strange behavior.
The most sensible use of this class will be will a LogContainer.
You can create one Logger instance for writing to (say) stderr,
a second for writing to a verbose log file, and a SysLogger
instance for writing important things to syslog so your automated
log-readers can see them. Then you put them all in a log container
for convenient access. That would go something like this:
from logger import Logger, SysLogger, LogContainer
fo = open(file_log, 'w')
file_logger = Logger(4, file_object=fo) # print 4 and lower
console_logger = Logger(1) # print 1 and lower
syslog_logger = SysLogger(0) # print 0 and lower
log = LogContainer([file_logger, console_logger, syslog_logger])
log(3, 'some debugging message') # printed to file only
log(1, 'some warning message') # printed to file and console
log(0, 'some error message') # printed to all (ERR level)
log(-1, 'major problem') # printed to all (CRIT level)
ATTRIBUTES:
(all of these are settable as keyword args to __init__)
ARGUMENT DEFAULT DESCRIPTION
----------------------------------------------------------
threshold = 0 identical to Logger threshold
ident = None string prepended to each log, if None,
it will be taken from the program name
as it appears in sys.argv[0]
logopt = 0 syslog log options
facility = 'LOG_USER' syslog facility (it can be a string)
maskpri = 0 syslog priority bitmask
default = 1 default priority to log at
"""
def __init__(self,
threshold = 0,
ident = None,
logopt = 0,
facility = 'LOG_USER',
maskpri = 0,
default = 1):
# putting imports here is kinda icky, but I don't want to import
# it if no SysLogger's are ever used.
global syslog
import syslog
self.threshold = threshold
self.default = default
if ident is None:
ind = string.rfind(sys.argv[0], '/')
if ind == -1: ident = sys.argv[0]
else: ident = sys.argv[0][ind+1:]
if type(facility) == type(''):
facility = getattr(syslog, facility)
syslog.openlog(ident, logopt, facility)
if maskpri: syslog.setlogmask(maskpri)
def setlogmask(self, maskpri):
"""a (very) thin wrapper over the syslog setlogmask function"""
return syslog.setlogmask(maskpri)
def map_priority(self, priority):
"""Take a logger priority and return a syslog priority
Here are the syslog priorities (from syslog.h):
LOG_EMERG 0 /* system is unusable */
LOG_ALERT 1 /* action must be taken immediately */
LOG_CRIT 2 /* critical conditions */
LOG_ERR 3 /* error conditions */
LOG_WARNING 4 /* warning conditions */
LOG_NOTICE 5 /* normal but significant condition */
LOG_INFO 6 /* informational */
LOG_DEBUG 7 /* debug-level messages */
The syslog priority is simply equal to the logger priority plus 3.
0 -> 0 + 3 = 3
-5 -> -5 + 3 = -2 (which will be treated as 0)
You can override this very simply. Just do:
def log_everything_emerg(priority): return 0
log_obj.map_priority = log_everything_emerg
The return value of this function does not need to be an integer or
within the allowed syslog range (0 to 7). It will be converted to
an int and forced into this range if it lies outside it.
"""
return priority + 3
def test(self, priority):
"""
Return true if a log of the given priority would be printed.
This can be overridden to do any test you like. Specifically,
threshold and threshold need not be integers. They can be
arbitrary objects. If you override this and use non-integer
priorities, you will also need to override map_priority.
"""
return int(self.threshold) >= int(priority)
def log(self, priority, message=None):
"""
Print a log message with some simple formatting.
"""
p, m = self._use_default(priority, message)
if self.test(p):
if type(m) == type(''): # message is a string
mlist = string.split(m, '\n')
if mlist[-1] == '': del mlist[-1] # string ends in \n
elif type(m) == type([]): # message is a list
mlist = map(string.rstrip, m)
else: mlist = [str(m)] # message is other type
sp = int(self.map_priority(p))
if sp < 0: sp = 0
if sp > 7: sp = 7
for line in mlist: syslog.syslog(sp, line)
# make the objects callable
__call__ = log
def write(self, priority, message=None):
"""
Print a log message.
"""
p, m = self._use_default(priority, message)
if self.test(p):
sp = int(self.map_priority(p))
if sp < 0: sp = 0
if sp > 7: sp = 7
# we must split based on newlines for syslog because
# it doesn't deal with them well
mlist = string.split(m, '\n')
if mlist[-1] == '': del mlist[-1] # string ends in \n
for message in mlist: syslog.syslog(sp, message)
def _use_default(self, priority, message):
"""Substitute default priority if none was provided"""
if message == None: return self.default, priority
else: return priority, message
class LogContainer:
"""A class for consolidating calls to multiple sub-objects
SUMMARY:
If you want a program to log to multiple destinations, it might
be convenient to use log containers. A log container is an
object which can hold several sub-log-objects (including other
log containers). When you log to a log container it passes the
message on (with optional tests) to each of the log objects it
contains.
USAGE:
The basic usage is very simple. LogContainer's simply pass on
logs to the contained Logger, SysLogger, or LogContainer
objects.
from logger import Logger, LogContainer
log_1 = Logger(threshold=1, file_object=sys.stdout)
log_2 = Logger(threshold=2, preprefix='LOG2')
log = LogContainer([log_1, log_2])
log(1, 'message') # printed by log_1 and log_2
log(2, 'message') # only printed by log_2
A more common example would be something like this:
from logger import Logger, LogContainer
system = Logger(threshold=1, file_object=logfile)
debug = Logger(threshold=5, file_object=sys.stdout)
log = LogContainer([system, debug])
log(3, 'sent to system and debug, but only debug will print it')
log(0, 'very important, both will print it')
In this mode, log containers are just shorthand for calling all
contained objects with the same priority and message.
When a log object is held in a container, it can still be used
directly. For example, you can still do
debug(3, ['this will not be sent to the system log, even if its',
' threshold is set very high'])
(Yes, you can send lists of strings and they will be formatted
on different lines. The log methods are pretty smart.)
There are more examples in the SysLogger docs.
ATTRIBUTES:
(all of these are settable as keyword args to __init__)
ATTRIBUTES DEFAULT DESCRIPTION
----------------------------------------------------------
list = [] list of contained objects
threshold = None meaning depends on test - by default
threshold has no effect
default = 1 default priority to log at
"""
def __init__(self, list=[], threshold=None, default=1):
self.list = list
self.threshold = threshold
self.default = default
def add(self, log_obj):
"""Add a log object to the container."""
self.list.append(log_obj)
def log(self, priority, message=None):
"""Log a message to all contained log objects, depending on
the results of test()
"""
p, m = self._use_default(priority, message)
for log_obj in self.list:
if self.test(p, m, self.threshold, log_obj):
log_obj.log(p, m)
__call__ = log
def write(self, priority, message=None):
p, m = self._use_default(priority, message)
for log_obj in self.list:
if self.test(p, m, self.threshold, log_obj):
log_obj.write(p, m)
def _use_default(self, priority, message):
"""Substitute default priority if none was provided"""
if message == None: return self.default, priority
else: return priority, message
def test(self, priority, message, threshold, log_obj):
"""Test which log objects should be passed a given message.
This method is used to determine if a given message (and
priority) should be passed on to a given log_obj. The
container's threshold is also provided.
This method always returns 1, and is the default, meaning that
all messages will get passed to all objects. It is intended
to be overridden if you want more complex behavior. To
override with your own function, just do something like:
def hell_no(p, m, t, object): return 0
container.test = hell_no
"""
return 1
def test_limit_priority(self, priority, message, threshold, log_obj):
"""Only pass on messages with sufficient priority compared to
the master threshold.
container = LogContainer([system, debug], threshold = 2)
container.test = container.test_limit_priority
"""
return priority <= threshold
def test_limit_threshold(self, priority, message, threshold, log_obj):
"""Only pass on messages to log objects whose threshold is
(numerically) lower than the master threshold.
container = LogContainer([system, debug], threshold = 2)
container.test = container.test_limit_threshold
"""
return log_obj.threshold <= threshold
if __name__ == '__main__':
###### TESTING AND DEMONSTRATION
threshold = 3
print 'THRESHOLD = %s' % (threshold)
log = Logger(threshold, preprefix = 'TEST ')
print " Lets log a few things!"
for i in range(-2, 10): log(i, 'log priority %s' % (i))
print "\n Now make it print the time for each log..."
import time
def printtime():
return time.strftime('%m/%d/%y %H:%M:%S ',time.localtime(time.time()))
log.preprefix = printtime
print " and log a few more things"
for i in range(-2, 10): log(i, 'log priority %s' % (i))
print "\n now create another with a different prefix and priority..."
print " and put them in a container..."
log2 = Logger(threshold-2, preprefix = 'LOG2 ')
cont = LogContainer([log, log2], threshold=0)
cont.test = cont.test_limit_priority
print " and log a bit more"
for i in range(-2, 10): cont(i, 'log priority %s' % (i))
print "\n OK, enough of the container... lets play with formatting"
stuff = 'abcd\nefgh\nijkl'
print "\n no trailing newline"
log(stuff)
print "\n with trailing newline"
log(stuff + '\n') # should be the same because the log method
# takes care of the newline for you
print "\n two trailing newlines"
log(stuff + '\n\n') # should create a "blank" line. If you use two
# newlines, it knows you really wanted one :)
print "\n log JUST a newline"
log('\n') # should create only a single "blank" line
print "\n use the write method, with a trailing newline"
log.write(stuff + '\n') # should just write with no prefix crap
# it will _NOT_ quietly tack on a newline
print "\n print some complex object"
log(1, {'key': 'value'}) # non-strings should be no trouble
print "\n now set the file object to None (nothing should be printed)"
log.file_object = None
log("THIS SHOULD NOT BE PRINTED")
log.write("THIS SHOULD NOT BE PRINTED")
if not (sys.argv[1:] and sys.argv[1] == 'syslog'):
print '\n skipping syslog test (because they would annoy your admin)'
print ' add "syslog" to the command line to enable syslog tests'
sys.exit(0)
print '\n performing syslog tests'
print ' creating logger with threshold: 3'
slog = SysLogger(3, 'logger-test')
print ' logging at (logger) priorities from -2 to 9 (but only'
print ' priorities <= 3 should show up'
for i in range(-2, 10): slog(i, 'log priority %s' % (i))
print '\n now test the write() method'
slog.write(0, 'first line\nsecond line\nthird line')
|