class Logging::Appender
The Appender
class is provides methods for appending log
events to a logging destination. The log events are formatted into strings
using a Layout.
All other Appenders inherit from this class
which provides stub methods. Each subclass should provide a
write
method that will write log messages to the logging
destination.
A private sync
method is provided for use by subclasses. It is
used to synchronize writes to the logging destination, and can be used by
subclasses to synchronize the closing or flushing of the logging
destination.
Attributes
Public Class Methods
Creates a new appender using the given name. If no Layout is specified, then a Basic layout will be used. Any logging header supplied by the layout will be written to the logging destination when the Appender is created.
Options:
:layout => the layout to use when formatting log events :level => the level at which to log :encoding => encoding to use when writing messages (defaults to UTF-8) :filters => filters to apply to events before processing
# File lib/logging/appender.rb, line 37 def initialize( name, opts = {} ) ::Logging.init unless ::Logging.initialized? @name = name.to_s @closed = false @filters = [] @mutex = ReentrantMutex.new self.layout = opts.fetch(:layout, ::Logging::Layouts::Basic.new) self.level = opts.fetch(:level, nil) self.encoding = opts.fetch(:encoding, self.encoding) self.filters = opts.fetch(:filters, nil) if opts.fetch(:header, true) header = @layout.header unless header.nil? || header.empty? begin write(header) rescue StandardError => err ::Logging.log_internal_error(err) end end end ::Logging::Appenders[@name] = self end
Public Instance Methods
Write the given string to the logging destination “as is” – no layout formatting will be performed.
# File lib/logging/appender.rb, line 96 def <<( str ) if @closed raise RuntimeError, "appender '<#{self.class.name}: #{@name}>' is closed" end unless off? begin write(str) rescue StandardError => err ::Logging.log_internal_error(err) end end self end
Sets the filter(s) to be used by this appender. The filters will be applied in the order that they are added to the appender.
Examples
add_filters(Logging::Filters::Level.new(:warn, :error))
Returns this appender instance.
# File lib/logging/appender.rb, line 185 def add_filters( *args ) args.flatten.each do |filter| next if filter.nil? unless filter.kind_of?(::Logging::Filter) raise TypeError, "#{filter.inspect} is not a kind of 'Logging::Filter'" end @filters << filter end self end
Check to see if the event should be processed by the appender. An event will be rejected if the event level is lower than the configured level for the appender. Or it will be rejected if one of the filters rejects the event.
event - The LogEvent to check
Returns the event if it is allowed; returns `nil` if it is not allowed.
# File lib/logging/appender.rb, line 298 def allow( event ) return nil if @level > event.level @filters.each do |filter| break unless event = filter.allow(event) end event end
Write the given event to the logging destination. The log event will be processed through the Layout associated with the Appender.
# File lib/logging/appender.rb, line 71 def append( event ) if @closed raise RuntimeError, "appender '<#{self.class.name}: #{@name}>' is closed" end # only append if the event level is less than or equal to the configured # appender level and the filter does not disallow it if event = allow(event) begin write(event) rescue StandardError => err ::Logging.log_internal_error(err) end end self end
Close the appender and writes the layout footer to the logging destination
if the footer flag is set to true
. Log events will no
longer be written to the logging destination after the appender is closed.
# File lib/logging/appender.rb, line 204 def close( footer = true ) return self if @closed ::Logging::Appenders.remove(@name) @closed = true flush if footer footer = @layout.footer unless footer.nil? || footer.empty? begin write(footer) rescue StandardError => err ::Logging.log_internal_error(err) end end end self end
Returns true
if the appender has been closed; returns
false
otherwise. When an appender is closed, no more log
events can be written to the logging destination.
# File lib/logging/appender.rb, line 231 def closed? @closed end
Returns the current Encoding for the appender or nil if an encoding has not been set.
# File lib/logging/appender.rb, line 269 def encoding return @encoding if defined? @encoding @encoding = Object.const_defined?(:Encoding) ? Encoding.default_external : nil end
Set the appender encoding to the given value. The value can either be an Encoding instance or a String or Symbol referring to a valid encoding.
This method only applies to Ruby 1.9 or later. The encoding will always be nil for older Rubies.
value - The encoding as a String, Symbol, or Encoding instance.
Raises ArgumentError if the value is not a valid encoding.
# File lib/logging/appender.rb, line 283 def encoding=( value ) if value.nil? @encoding = nil else @encoding = Object.const_defined?(:Encoding) ? Encoding.find(value.to_s) : nil end end
Sets the filter(s) to be used by this appender. This method will clear the current filter set and add those passed to this setter method.
Examples
appender.filters = Logging::Filters::Level.new(:warn, :error)
# File lib/logging/appender.rb, line 173 def filters=( args ) @filters.clear add_filters(*args) end
Call flush
to force an appender to write out any buffered log
events. Similar to IO#flush, so use in a similar fashion.
# File lib/logging/appender.rb, line 250 def flush self end
call-seq
appender.layout = Logging::Layouts::Basic.new
Sets the layout to be used by this appender.
# File lib/logging/appender.rb, line 159 def layout=( layout ) unless layout.kind_of? ::Logging::Layout raise TypeError, "#{layout.inspect} is not a kind of 'Logging::Layout'" end @layout = layout end
Set the level for this appender; log events below this level will be
ignored by this appender. 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 recording of all log events. The latter will disable the recording of all events.
Example:
appender.level = :debug appender.level = "INFO" appender.level = 4 appender.level = 'off' appender.level = :all
These produce an ArgumentError
appender.level = Object appender.level = -1 appender.level = 1_000_000_000_000
# File lib/logging/appender.rb, line 138 def level=( level ) lvl = case level when String, Symbol; ::Logging::level_num(level) when Integer; level when nil; 0 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 @level = lvl end
Returns `true` if the appender has been turned off. This is useful for appenders that write data to a remote location (such as syslog or email), and that write encounters too many errors. The appender can turn itself off to and log an error via the `Logging` logger.
Set the appender's level to a valid value to turn it back on.
# File lib/logging/appender.rb, line 312 def off? @level >= ::Logging::LEVELS.length end
Reopen the connection to the underlying logging destination. If the connection is currently closed then it will be opened. If the connection is currently open then it will be closed and immediately opened.
# File lib/logging/appender.rb, line 239 def reopen @closed = false self end
Returns a string representation of the appender.
# File lib/logging/appender.rb, line 262 def to_s "<%s name=\"%s\">" % [self.class.name.sub(%r/^Logging::/, ''), self.name] end
Private Instance Methods
Obtains an exclusive lock, runs the block, and releases the lock when the
block completes. This method is re-entrant so that a single thread can call
sync
multiple times without hanging the thread.
# File lib/logging/appender.rb, line 338 def sync( &block ) @mutex.synchronize(&block) end
Writes the given event to the logging destination. Subclasses should provide an implementation of this method. The event can be either a LogEvent or a String. If a LogEvent, then it will be formatted using the layout given to the appender when it was created.
# File lib/logging/appender.rb, line 327 def write( event ) nil end