Logging from inside your daemon

Proper logging inside your daemon process is critical, and daemon-kit provides you with a great logging facility to (ab)use.

Logging examples

From anywhere in your code you can access the DaemonKit.logger instance, which is a configured DaemonKit::AbstractLogger. It is compatible with Ruby's Logger class but is much more verbose to help you gain some insight into your running process.

DaemonKit.logger.info( "Hello world" )

This logs a 'Hello world' line to the log file, complete with the calling file name and line number. Log lines look something like this:

2009-06-07 23:21:30.248575 capd(32513) [INFO] initializer.rb:91: DaemonKit (0.1.7.4) booted, now running capd

Log as much as you can, but be careful not to abuse the info level since your log files can become huge. For general processing hints, use the debug level.

To log exceptions, use the special exception helper:

begin
  # dangerous operation
rescue => e
  DaemonKit.logger.exception( e )
end

Controlling logging in a running process

Logging can be controlled in a running process, either via code or by sending UNIX signals to the running process.

Changing log levels in your code

Log levels can be toggled with the level= method:

DaemonKit.logger.level = :info

Alternatively you can silence all the logging activity for a while using the silence helper:

DaemonKit.logger.silence do |logger|
  # logger will only report :error or higher levels
end

You can also set the logging per environment by editing the correct file in config/environments

config.log_level = :debug

Changing log levels via UNIX signals

Send your process the USR1 signal to toggle between :debug and :info log levels. Sending a USR2 signal will force the logger into :debug mode (USR1 will revert).

Support for log rotation

Support for logrotate is baked right into daemon-kit. By sending your daemon a HUP signal all the log files file be closed and re-opened again on first use. Here is an example logrotate configuration:

/path/to/daemon.log {
  rotate 5
  weekly
  postrotate
    kill -HUP `cat /path/to/daemon.pid`
  endscript
}

Support for syslog logging

If you have the SyslogLogger gem installed, you can have your process log to a UNIX syslog server. You can change the logging to syslog by either updating your environment.rb file like this:

config.log_path = :syslog

Or by passing 'syslog' as the logfile argument when starting a daemon

$ ruby ./bin/daemon start -l syslog

The SyslogLogger rdoc's provide configuration examples for configuring various UNIX syslog servers.

More logging information

If you're running your daemon in the foreground (with the run command, you'll get copies of all the log messages on STDOUT, and thus voiding the need to tail log files the whole time.

[Validate]

Generated with the Darkfish Rdoc Generator 2.