Outputters¶ ↑
An Outputter is a logging destination with a particular way to format data. It has a level threshold and a flexible level mask.
Outputters must have names.
Level Threshold¶ ↑
Outputters have their own level thresholds that default to root
level. They will not write any log events with a rank less than their threshold.
Level Mask¶ ↑
Alternatively, an Outputter can be told to log specific levels only:
o = StdoutOutputter.new 'console' o.only_at DEBUG, FATAL # only DEBUG and FATAL get written
Outputter Repository¶ ↑
When outputters are created, they store themselves in an Outputter repository similar to the Logger repository.
StdoutOutputter.new 'console' => Create 'console' outputter Outputter['console'] => Get it back from the stash.
Formatter¶ ↑
An outputter has a format defined by its Formatter. If no Formatter is specified, DefaultFormatter will be used.
Outputter is Abstract¶ ↑
The basic Outputter class is both abstract and a null object.
Interesting Outputters¶ ↑
-
log4r/outputter/syslogoutputter.rb - Logs to syslog
-
log4r/outputter/emailoutputter.rb - Email logs
-
log4r/logserver.rb - For remote logging
Subclasses¶ ↑
-
Log4r::IOOutputter
- for any IO object -
Log4r::StdoutOutputter
- $stdout -
Log4r::StderrOutputter
- $stderr -
Log4r::FileOutputter
- log to a file -
Log4r::RollingFileOutputter
- log to a file and split it as it grows -
Log4r::SyslogOutputter
- logs to syslog -
Log4r::EmailOutputter
- email logs -
Log4r::RemoteOutputter
- for remote logging
Default Outputters¶ ↑
Two outputters named ‘stdout’ and ‘stderr’ are created automatically at the root level. They are nice shortcuts.
Outputter['stdout'] => 'stdout' Outputter['stderr'] => 'stderr' Outputter.stdout => 'stdout' Outputter.stderr => 'stderr'
Configuring¶ ↑
Outputters must have names and receive hash arguments. The parameter name for the hash args can be either a symbol or a string. All defined outputters accept :level
and :formatter
arguments. For arguments specific to a convenience Outputter, please look at the class description.
The level threshold, the levels to log at (only_at) and formatter can be changed dynamically using the =
methods.
As a collective example of all this, here are various ways to set up an IOOutputter:
IOOutputter.new ExoticIO.new 'exotic', 'level' => WARN, :formatter => MyFormatter.new # an equivalent way: o = IOOutputter.new ExoticIO.new 'exotic' o.level = WARN o.formatter = MyFormatter # we can specify just the class o.only_at = THIS, THAT
XML Configuration¶ ↑
Specify outputters as children of <log4r_config>
:
<log4r_config> <outputter name="myout" type="Log4r::StdoutOutputter"> <only_at>DEBUG, INFO</only_at> </outputter> <outputter name="file" level="WARN"> <type>FileOutputter</type> <filename>#{logpath}/file.log</filename> <trunc>false</trunc> </outputter> ...
As explained in log4r/configurator.rb, the hash arguments you would normally pass to new
are specified as XML parameters. It is given an IO object to write to, a Formatter to call, and, optionally, levels to write at.
Outputters invoke print then flush on the wrapped IO object. If the IO chokes, the Outputter will close the IO and set its level to OFF
.