ioquatix/process-daemon

# Copyright, 2014, by Samuel G. D. Williams. <http://www.codeotaku.com>
# 
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
# 
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
# 
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.

require 'fileutils'

module Process
    class Daemon
        # This module controls the storage and retrieval of process id files.
        class ProcessFile
            # Saves the pid for the given daemon
            def self.store(daemon, pid)
                File.write(daemon.process_file_path, pid)
            end

            # Retrieves the pid for the given daemon
            def self.recall(daemon)
                File.read(daemon.process_file_path).to_i rescue nil
            end

            # Removes the pid saved for a particular daemon
            def self.clear(daemon)
                if File.exist? daemon.process_file_path
                    FileUtils.rm(daemon.process_file_path)
                end
            end

            # Checks whether the daemon is running by checking the saved pid and checking the corresponding process
            def self.running(daemon)
                pid = recall(daemon)

                return false if pid == nil

                gpid = Process.getpgid(pid) rescue nil

                return gpid != nil ? true : false
            end

            # Remove the pid file if the daemon is not running
            def self.cleanup(daemon)
                clear(daemon) unless running(daemon)
            end

            # This function returns the status of the daemon. This can be one of +:running+, +:unknown+ (pid file exists but no 
            # corresponding process can be found) or +:stopped+.
            def self.status(daemon)
                if File.exist? daemon.process_file_path
                    return ProcessFile.running(daemon) ? :running : :unknown
                else
                    return :stopped
                end
            end
        end
    end
end