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# logger.rb - simple logging utility
# Copyright (C) 2000-2003, 2005 NAKAMURA, Hiroshi <nakahiro@sarion.co.jp>.
require 'monitor'
# Simple logging utility.
#
# Author:: NAKAMURA, Hiroshi <nakahiro@sarion.co.jp>
# Documentation:: NAKAMURA, Hiroshi and Gavin Sinclair
# License::
# You can redistribute it and/or modify it under the same terms of Ruby's
# license; either the dual license version in 2003, or any later version.
# Revision:: $Id: logger.rb 31806 2011-05-30 02:08:57Z nahi $
#
# == Description
#
# The Logger class provides a simple but sophisticated logging utility that
# anyone can use because it's included in the Ruby 1.8.x standard library.
#
# The HOWTOs below give a code-based overview of Logger's usage, but the basic
# concept is as follows. You create a Logger object (output to a file or
# elsewhere), and use it to log messages. The messages will have varying
# levels (+info+, +error+, etc), reflecting their varying importance. The
# levels, and their meanings, are:
#
# +FATAL+:: an unhandleable error that results in a program crash
# +ERROR+:: a handleable error condition
# +WARN+:: a warning
# +INFO+:: generic (useful) information about system operation
# +DEBUG+:: low-level information for developers
#
# So each message has a level, and the Logger itself has a level, which acts
# as a filter, so you can control the amount of information emitted from the
# logger without having to remove actual messages.
#
# For instance, in a production system, you may have your logger(s) set to
# +INFO+ (or +WARN+ if you don't want the log files growing large with
# repetitive information). When you are developing it, though, you probably
# want to know about the program's internal state, and would set them to
# +DEBUG+.
#
# === Example
#
# A simple example demonstrates the above explanation:
#
# log = Logger.new(STDOUT)
# log.level = Logger::WARN
#
# log.debug("Created logger")
# log.info("Program started")
# log.warn("Nothing to do!")
#
# begin
# File.each_line(path) do |line|
# unless line =~ /^(\w+) = (.*)$/
# log.error("Line in wrong format: #{line}")
# end
# end
# rescue => err
# log.fatal("Caught exception; exiting")
# log.fatal(err)
# end
#
# Because the Logger's level is set to +WARN+, only the warning, error, and
# fatal messages are recorded. The debug and info messages are silently
# discarded.
#
# === Features
#
# There are several interesting features that Logger provides, like
# auto-rolling of log files, setting the format of log messages, and
# specifying a program name in conjunction with the message. The next section
# shows you how to achieve these things.
#
#
# == HOWTOs
#
# === How to create a logger
#
# The options below give you various choices, in more or less increasing
# complexity.
#
# 1. Create a logger which logs messages to STDERR/STDOUT.
#
# logger = Logger.new(STDERR)
# logger = Logger.new(STDOUT)
#
# 2. Create a logger for the file which has the specified name.
#
# logger = Logger.new('logfile.log')
#
# 3. Create a logger for the specified file.
#
# file = File.open('foo.log', File::WRONLY | File::APPEND)
# # To create new (and to remove old) logfile, add File::CREAT like;
# # file = open('foo.log', File::WRONLY | File::APPEND | File::CREAT)
# logger = Logger.new(file)
#
# 4. Create a logger which ages logfile once it reaches a certain size. Leave
# 10 "old log files" and each file is about 1,024,000 bytes.
#
# logger = Logger.new('foo.log', 10, 1024000)
#
# 5. Create a logger which ages logfile daily/weekly/monthly.
#
# logger = Logger.new('foo.log', 'daily')
# logger = Logger.new('foo.log', 'weekly')
# logger = Logger.new('foo.log', 'monthly')
#
# === How to log a message
#
# Notice the different methods (+fatal+, +error+, +info+) being used to log
# messages of various levels. Other methods in this family are +warn+ and
# +debug+. +add+ is used below to log a message of an arbitrary (perhaps
# dynamic) level.
#
# 1. Message in block.
#
# logger.fatal { "Argument 'foo' not given." }
#
# 2. Message as a string.
#
# logger.error "Argument #{ @foo } mismatch."
#
# 3. With progname.
#
# logger.info('initialize') { "Initializing..." }
#
# 4. With severity.
#
# logger.add(Logger::FATAL) { 'Fatal error!' }
#
# === How to close a logger
#
# logger.close
#
# === Setting severity threshold
#
# 1. Original interface.
#
# logger.sev_threshold = Logger::WARN
#
# 2. Log4r (somewhat) compatible interface.
#
# logger.level = Logger::INFO
#
# DEBUG < INFO < WARN < ERROR < FATAL < UNKNOWN
#
#
# == Format
#
# Log messages are rendered in the output stream in a certain format. The
# default format and a sample are shown below:
#
# Log format:
# SeverityID, [Date Time mSec #pid] SeverityLabel -- ProgName: message
#
# Log sample:
# I, [Wed Mar 03 02:34:24 JST 1999 895701 #19074] INFO -- Main: info.
#
# You may change the date and time format in this manner:
#
# logger.datetime_format = "%Y-%m-%d %H:%M:%S"
# # e.g. "2004-01-03 00:54:26"
#
# There is currently no supported way to change the overall format, but you may
# have some luck hacking the Format constant.
#
class Logger
VERSION = "1.2.6"
ProgName = "#{File.basename(__FILE__)}/#{VERSION}"
class Error < RuntimeError; end
class ShiftingError < Error; end
# Logging severity.
module Severity
DEBUG = 0
INFO = 1
WARN = 2
ERROR = 3
FATAL = 4
UNKNOWN = 5
end
include Severity
# Logging severity threshold (e.g. <tt>Logger::INFO</tt>).
attr_accessor :level
# Logging program name.
attr_accessor :progname
# Logging date-time format (string passed to +strftime+).
def datetime_format=(datetime_format)
@default_formatter.datetime_format = datetime_format
end
def datetime_format
@default_formatter.datetime_format
end
# Logging formatter. formatter#call is invoked with 4 arguments; severity,
# time, progname and msg for each log. Bear in mind that time is a Time and
# msg is an Object that user passed and it could not be a String. It is
# expected to return a logdev#write-able Object. Default formatter is used
# when no formatter is set.
attr_accessor :formatter
alias sev_threshold level
alias sev_threshold= level=
# Returns +true+ iff the current severity level allows for the printing of
# +DEBUG+ messages.
def debug?; @level <= DEBUG; end
# Returns +true+ iff the current severity level allows for the printing of
# +INFO+ messages.
def info?; @level <= INFO; end
# Returns +true+ iff the current severity level allows for the printing of
# +WARN+ messages.
def warn?; @level <= WARN; end
# Returns +true+ iff the current severity level allows for the printing of
# +ERROR+ messages.
def error?; @level <= ERROR; end
# Returns +true+ iff the current severity level allows for the printing of
# +FATAL+ messages.
def fatal?; @level <= FATAL; end
#
# === Synopsis
#
# Logger.new(name, shift_age = 7, shift_size = 1048576)
# Logger.new(name, shift_age = 'weekly')
#
# === Args
#
# +logdev+::
# The log device. This is a filename (String) or IO object (typically
# +STDOUT+, +STDERR+, or an open file).
# +shift_age+::
# Number of old log files to keep, *or* frequency of rotation (+daily+,
# +weekly+ or +monthly+).
# +shift_size+::
# Maximum logfile size (only applies when +shift_age+ is a number).
#
# === Description
#
# Create an instance.
#
def initialize(logdev, shift_age = 0, shift_size = 1048576)
@progname = nil
@level = DEBUG
@default_formatter = Formatter.new
@formatter = nil
@logdev = nil
if logdev
@logdev = LogDevice.new(logdev, :shift_age => shift_age,
:shift_size => shift_size)
end
end
#
# === Synopsis
#
# Logger#add(severity, message = nil, progname = nil) { ... }
#
# === Args
#
# +severity+::
# Severity. Constants are defined in Logger namespace: +DEBUG+, +INFO+,
# +WARN+, +ERROR+, +FATAL+, or +UNKNOWN+.
# +message+::
# The log message. A String or Exception.
# +progname+::
# Program name string. Can be omitted. Treated as a message if no +message+ and
# +block+ are given.
# +block+::
# Can be omitted. Called to get a message string if +message+ is nil.
#
# === Return
#
# +true+ if successful, +false+ otherwise.
#
# When the given severity is not high enough (for this particular logger), log
# no message, and return +true+.
#
# === Description
#
# Log a message if the given severity is high enough. This is the generic
# logging method. Users will be more inclined to use #debug, #info, #warn,
# #error, and #fatal.
#
# <b>Message format</b>: +message+ can be any object, but it has to be
# converted to a String in order to log it. Generally, +inspect+ is used
# if the given object is not a String.
# A special case is an +Exception+ object, which will be printed in detail,
# including message, class, and backtrace. See #msg2str for the
# implementation if required.
#
# === Bugs
#
# * Logfile is not locked.
# * Append open does not need to lock file.
# * But on the OS which supports multi I/O, records possibly be mixed.
#
def add(severity, message = nil, progname = nil, &block)
severity ||= UNKNOWN
if @logdev.nil? or severity < @level
return true
end
progname ||= @progname
if message.nil?
if block_given?
message = yield
else
message = progname
progname = @progname
end
end
@logdev.write(
format_message(format_severity(severity), Time.now, progname, message))
true
end
alias log add
#
# Dump given message to the log device without any formatting. If no log
# device exists, return +nil+.
#
def <<(msg)
unless @logdev.nil?
@logdev.write(msg)
end
end
#
# Log a +DEBUG+ message.
#
# See #info for more information.
#
def debug(progname = nil, &block)
add(DEBUG, nil, progname, &block)
end
#
# Log an +INFO+ message.
#
# The message can come either from the +progname+ argument or the +block+. If
# both are provided, then the +block+ is used as the message, and +progname+
# is used as the program name.
#
# === Examples
#
# logger.info("MainApp") { "Received connection from #{ip}" }
# # ...
# logger.info "Waiting for input from user"
# # ...
# logger.info { "User typed #{input}" }
#
# You'll probably stick to the second form above, unless you want to provide a
# program name (which you can do with <tt>Logger#progname=</tt> as well).
#
# === Return
#
# See #add.
#
def info(progname = nil, &block)
add(INFO, nil, progname, &block)
end
#
# Log a +WARN+ message.
#
# See #info for more information.
#
def warn(progname = nil, &block)
add(WARN, nil, progname, &block)
end
#
# Log an +ERROR+ message.
#
# See #info for more information.
#
def error(progname = nil, &block)
add(ERROR, nil, progname, &block)
end
#
# Log a +FATAL+ message.
#
# See #info for more information.
#
def fatal(progname = nil, &block)
add(FATAL, nil, progname, &block)
end
#
# Log an +UNKNOWN+ message. This will be printed no matter what the logger
# level.
#
# See #info for more information.
#
def unknown(progname = nil, &block)
add(UNKNOWN, nil, progname, &block)
end
#
# Close the logging device.
#
def close
@logdev.close if @logdev
end
private
# Severity label for logging. (max 5 char)
SEV_LABEL = %w(DEBUG INFO WARN ERROR FATAL ANY)
def format_severity(severity)
SEV_LABEL[severity] || 'ANY'
end
def format_message(severity, datetime, progname, msg)
(@formatter || @default_formatter).call(severity, datetime, progname, msg)
end
class Formatter
Format = "%s, [%s#%d] %5s -- %s: %s\n"
attr_accessor :datetime_format
def initialize
@datetime_format = nil
end
def call(severity, time, progname, msg)
Format % [severity[0..0], format_datetime(time), $$, severity, progname,
msg2str(msg)]
end
private
def format_datetime(time)
if @datetime_format.nil?
time.strftime("%Y-%m-%dT%H:%M:%S.") << "%06d " % time.usec
else
time.strftime(@datetime_format)
end
end
def msg2str(msg)
case msg
when ::String
msg
when ::Exception
"#{ msg.message } (#{ msg.class })\n" <<
(msg.backtrace || []).join("\n")
else
msg.inspect
end
end
end
class LogDevice
attr_reader :dev
attr_reader :filename
class LogDeviceMutex
include MonitorMixin
end
def initialize(log = nil, opt = {})
@dev = @filename = @shift_age = @shift_size = nil
@mutex = LogDeviceMutex.new
if log.respond_to?(:write) and log.respond_to?(:close)
@dev = log
else
@dev = open_logfile(log)
@dev.sync = true
@filename = log
@shift_age = opt[:shift_age] || 7
@shift_size = opt[:shift_size] || 1048576
end
end
def write(message)
@mutex.synchronize do
if @shift_age and @dev.respond_to?(:stat)
begin
check_shift_log
rescue
raise Logger::ShiftingError.new("Shifting failed. #{$!}")
end
end
@dev.write(message)
end
end
def close
@mutex.synchronize do
@dev.close
end
end
private
def open_logfile(filename)
if (FileTest.exist?(filename))
open(filename, (File::WRONLY | File::APPEND))
else
create_logfile(filename)
end
end
def create_logfile(filename)
logdev = open(filename, (File::WRONLY | File::APPEND | File::CREAT))
logdev.sync = true
add_log_header(logdev)
logdev
end
def add_log_header(file)
file.write(
"# Logfile created on %s by %s\n" % [Time.now.to_s, Logger::ProgName]
)
end
SiD = 24 * 60 * 60
def check_shift_log
if @shift_age.is_a?(Integer)
# Note: always returns false if '0'.
if @filename && (@shift_age > 0) && (@dev.stat.size > @shift_size)
shift_log_age
end
else
now = Time.now
if @dev.stat.mtime <= previous_period_end(now)
shift_log_period(now)
end
end
end
def shift_log_age
(@shift_age-3).downto(0) do |i|
if FileTest.exist?("#{@filename}.#{i}")
File.rename("#{@filename}.#{i}", "#{@filename}.#{i+1}")
end
end
@dev.close
File.rename("#{@filename}", "#{@filename}.0")
@dev = create_logfile(@filename)
return true
end
def shift_log_period(now)
postfix = previous_period_end(now).strftime("%Y%m%d") # YYYYMMDD
age_file = "#{@filename}.#{postfix}"
if FileTest.exist?(age_file)
raise RuntimeError.new("'#{ age_file }' already exists.")
end
@dev.close
File.rename("#{@filename}", age_file)
@dev = create_logfile(@filename)
return true
end
def previous_period_end(now)
case @shift_age
when /^daily$/
eod(now - 1 * SiD)
when /^weekly$/
eod(now - ((now.wday + 1) * SiD))
when /^monthly$/
eod(now - now.mday * SiD)
else
now
end
end
def eod(t)
Time.mktime(t.year, t.month, t.mday, 23, 59, 59)
end
end
#
# == Description
#
# Application -- Add logging support to your application.
#
# == Usage
#
# 1. Define your application class as a sub-class of this class.
# 2. Override 'run' method in your class to do many things.
# 3. Instantiate it and invoke 'start'.
#
# == Example
#
# class FooApp < Application
# def initialize(foo_app, application_specific, arguments)
# super('FooApp') # Name of the application.
# end
#
# def run
# ...
# log(WARN, 'warning', 'my_method1')
# ...
# @log.error('my_method2') { 'Error!' }
# ...
# end
# end
#
# status = FooApp.new(....).start
#
class Application
include Logger::Severity
attr_reader :appname
attr_reader :logdev
#
# == Synopsis
#
# Application.new(appname = '')
#
# == Args
#
# +appname+:: Name of the application.
#
# == Description
#
# Create an instance. Log device is +STDERR+ by default. This can be
# changed with #set_log.
#
def initialize(appname = nil)
@appname = appname
@log = Logger.new(STDERR)
@log.progname = @appname
@level = @log.level
end
#
# Start the application. Return the status code.
#
def start
status = -1
begin
log(INFO, "Start of #{ @appname }.")
status = run
rescue
log(FATAL, "Detected an exception. Stopping ... #{$!} (#{$!.class})\n" << $@.join("\n"))
ensure
log(INFO, "End of #{ @appname }. (status: #{ status.to_s })")
end
status
end
#
# Sets the log device for this application. See the class Logger for an
# explanation of the arguments.
#
def set_log(logdev, shift_age = 0, shift_size = 1024000)
@log = Logger.new(logdev, shift_age, shift_size)
@log.progname = @appname
@log.level = @level
end
def log=(logdev)
set_log(logdev)
end
#
# Set the logging threshold, just like <tt>Logger#level=</tt>.
#
def level=(level)
@level = level
@log.level = @level
end
#
# See Logger#add. This application's +appname+ is used.
#
def log(severity, message = nil, &block)
@log.add(severity, message, @appname, &block) if @log
end
private
def run
raise RuntimeError.new('Method run must be defined in the derived class.')
end
end
end