class Logging::Logger
The Logger
class is the primary interface to the
Logging
framework. It provides the logging methods that will
be called from user methods, and it generates logging events that are sent
to the appenders (the appenders take care of sending the log events to the
logging destinations – files, sockets, etc).
Logger
instances are obtained from the Repository
and should not be directly created by users.
Example:
log = Logging.logger['my logger'] log.add_appenders( Logging.appenders.stdout ) # append to STDOUT log.level = :info # log 'info' and above log.info 'starting foo operation' ... log.info 'finishing foo operation' ... log.fatal 'unknown exception', exception
Attributes
Public Class Methods
Returns a logger instance for the given name.
# File lib/logging/logger.rb, line 45 def self.[]( name ) repo = ::Logging::Repository.instance name = repo.to_key(name) logger = repo[name] return logger unless logger.nil? @mutex.synchronize do logger = repo[name] return logger unless logger.nil? # thread-safe double checking logger = instantiate(name) repo[name] = logger repo.children(name).each { |child| child.__send__(:parent=, logger) } logger end end
This is where the actual logging methods are defined. Two methods are created for each log level. The first is a query method used to determine if that perticular logging level is enabled. The second is the actual logging method that accepts a list of objects to be logged or a block. If a block is given, then the object returned from the block will be logged.
Example
log = Logging::Logger['my logger'] log.level = :warn log.info? # => false log.warn? # => true log.warn 'this is your last warning' log.fatal 'I die!', exception log.debug do # expensive method to construct log message msg end
# File lib/logging/logger.rb, line 84 def self.define_log_methods( logger ) code = log_methods_for_level(logger.level) logger._meta_eval(code, __FILE__, __LINE__) logger end
This generator is used to define the log methods for the given `level`. This code is evaluated in the context of a Logger instance.
Returns log methods as a String
# File lib/logging/logger.rb, line 94 def self.log_methods_for_level( level ) code = [] ::Logging::LEVELS.each do |name,num| code << <<-CODE undef :#{name} if method_defined? :#{name} undef :#{name}? if method_defined? :#{name}? CODE if level > num code << <<-CODE def #{name}?( ) false end def #{name}( data = nil ) false end CODE else code << <<-CODE def #{name}?( ) true end def #{name}( data = nil ) data = yield if block_given? log_event(::Logging::LogEvent.new(@name, #{num}, data, @caller_tracing)) true end CODE end end code.join("\n") end
Overrides the new method such that only one Logger will be created for any given logger name.
# File lib/logging/logger.rb, line 40 def self.new( *args ) args.empty? ? super : self[args.shift] end
Returns the logger identified by name.
When name is a String
or a Symbol
it
will be used “as is” to retrieve the logger. When name is a
Class
the class name will be used to retrieve the logger. When
name is an object the name of the object's class will be used
to retrieve the logger.
Example:
obj = MyClass.new log1 = Logger.new(obj) log2 = Logger.new(MyClass) log3 = Logger['MyClass'] log1.object_id == log2.object_id # => true log2.object_id == log3.object_id # => true
# File lib/logging/logger.rb, line 145 def initialize( name ) case name when String raise(ArgumentError, "logger must have a name") if name.empty? else raise(ArgumentError, "logger name must be a String") end repo = ::Logging::Repository.instance _setup(name, :parent => repo.parent(name)) end
Returns the root logger.
# File lib/logging/logger.rb, line 30 def self.root ::Logging::Repository.instance[:root] end
Public Instance Methods
Log the given message without any formatting and without performing any
level checks. The message is logged to all appenders. The message is passed
up the logger tree if this logger's additivity is true
.
# File lib/logging/logger.rb, line 176 def <<( msg ) @appenders.each {|a| a << msg} @parent << msg if @additive end
Compares this logger by name to another logger. The normal return codes for
String
objects apply.
# File lib/logging/logger.rb, line 161 def <=>( other ) case other when self; 0 when ::Logging::RootLogger; 1 when ::Logging::Logger; @name <=> other.name else raise ArgumentError, 'expecting a Logger instance' end end
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.
Message format: message
can be any object,
but it has to be converted to a String in
order to log it. The Logging.format_as method is
used to determine how objects chould be converted to strings. Generally,
inspect
is used.
A special case is an Exception
object, which will be printed
in detail, including message, class, and backtrace.
If a message is not given, then the return value from the block is used as the message to log. This is useful when creating the actual message is an expensive operation. This allows the logger to check the severity against the configured level before actually constructing the message.
This method returns true
if the message was logged, and
false
is returned if the message was not logged.
# File lib/logging/logger.rb, line 206 def add( lvl, data = nil, progname = nil ) lvl = Integer(lvl) return false if lvl < level if data.nil? if block_given? data = yield else data = progname end end log_event(::Logging::LogEvent.new(@name, lvl, data, @caller_tracing)) true end
Add the given appenders to the list of appenders, where appenders can be either a single appender or an array of appenders.
# File lib/logging/logger.rb, line 340 def add_appenders( *args ) args.flatten.each do |arg| o = arg.kind_of?(::Logging::Appender) ? arg : ::Logging::Appenders[arg.to_s] raise ArgumentError, "unknown appender #{arg.inspect}" if o.nil? @appenders << o unless @appenders.include?(o) end self end
Sets the additivity of the logger. Acceptable values are true
,
'true', false
, 'false', or nil
.
In this case nil
does not change the additivity
# File lib/logging/logger.rb, line 229 def additive=( val ) @additive = case val when true, 'true'; true when false, 'false'; false when nil; @additive else raise ArgumentError, 'expecting a boolean' end end
Returns the list of appenders.
# File lib/logging/logger.rb, line 319 def appenders @appenders.dup end
Clears the current list of appenders and replaces them with app, where app can be either a single appender or an array of appenders.
# File lib/logging/logger.rb, line 329 def appenders=( args ) @appenders.clear add_appenders(*args) unless args.nil? end
Sets the caller tracing of the logger. Acceptable values are
true
, 'true', false
, 'false', or
nil
. In this case nil
does not change the
tracing.
# File lib/logging/logger.rb, line 244 def caller_tracing=( val ) @caller_tracing = case val when true, 'true'; true when false, 'false'; false when nil; @caller_tracing else raise ArgumentError, 'expecting a boolean' end end
Remove all appenders from this logger.
# File lib/logging/logger.rb, line 376 def clear_appenders( ) @appenders.clear end
Returns `true` if the logger has its own level defined.
# File lib/logging/logger.rb, line 313 def has_own_level? !@level.nil? end
Returns an integer which is the defined log level for this logger.
# File lib/logging/logger.rb, line 258 def level return @level unless @level.nil? @parent.level end
Set the level for this logger. The level can be either a
String
, a Symbol
, or an Integer
. An
ArgumentError
is raised if this is not the case.
There are two special levels – “all” and “off”. The former will enable log messages from this logger. The latter will disable all log messages from this logger.
Setting the logger level to nil
will cause the parent's
logger level to be used.
Example:
log.level = :debug log.level = "INFO" log.level = 4 log.level = 'off' log.level = :all
These produce an ArgumentError
log.level = Object log.level = -1 log.level = 1_000_000_000_000
# File lib/logging/logger.rb, line 291 def level=( level ) @level = if level.nil? then level else lvl = case level when String, Symbol; ::Logging::level_num(level) when Integer; level else raise ArgumentError, "level must be a String, Symbol, or Integer" end if lvl.nil? or lvl < 0 or lvl > ::Logging::LEVELS.length raise ArgumentError, "unknown level was given '#{level}'" end lvl end define_log_methods(true) self.level end
Remove the given appenders from the list of appenders. The
appenders to remove can be identified either by name using a
String
or by passing the appender instance. appenders
can be a single appender or an array of appenders.
# File lib/logging/logger.rb, line 357 def remove_appenders( *args ) args.flatten.each do |arg| @appenders.delete_if do |a| case arg when String; arg == a.name when ::Logging::Appender; arg.object_id == a.object_id else raise ArgumentError, "#{arg.inspect} is not a 'Logging::Appender'" end end end self end
Protected Instance Methods
Define the logging methods for this logger based on the configured log level. If the level is nil, then we will ask our parent for it's level and define log levels accordingly. The force flag will skip this check.
Recursively call this method on all our children loggers.
# File lib/logging/logger.rb, line 411 def define_log_methods( force = false, code = nil ) return if has_own_level? and !force ::Logging::Logger._reentrant_mutex.synchronize do ::Logging::Logger.define_log_methods(self) ::Logging::Repository.instance.children(name).each do |child| child.define_log_methods end end self end
Send the given event to the appenders for logging, and pass the event up to the parent if additive mode is enabled. The log level has already been checked before this method is called.
# File lib/logging/logger.rb, line 396 def log_event( event ) @appenders.each {|a| a.append(event)} @parent.log_event(event) if @additive end
Set the parent logger for this logger. This method will be invoked by the
Repository
class when a parent or child is added to the
hierarchy.
# File lib/logging/logger.rb, line 387 def parent=( parent ) @parent = parent end