Process::Daemon

Process::Daemon is a stable and helpful base class for long running tasks and daemons. Provides standard start, stop, restart, status operations.

Installation

Add this line to your application's Gemfile:

    gem 'process-daemon'

And then execute:

    $ bundle

Or install it yourself as:

    $ gem install process-daemon

Usage

A process daemon has a specific structure:

class MyDaemon < Process::Daemon
    def startup
        # Called when the daemon is initialized in it's own process. Should return quickly.
    end

    def run
        # Do the actual work. Does not need to be implemented, e.g. if using threads or other background processing mechanisms which were kicked off in #startup.
    end

    def shutdown
        # Stop everything that was setup in startup. Called as part of main daemon thread/process, not in trap context (e.g. SIGINT).
        # Asynchronous code can call self.request_shutdown from a trap context to interrupt the main process, provided you aren't doing work in #run.
    end
end

# Make this file executable and have a command line interface:
MyDaemon.daemonize

Working directory

By default, daemons run in the current working directory. They setup paths according to the following logic:

working_directory = "."
log_directory = #{working_directory}/log
log_file_path = #{log_directory}/#{name}.log
runtime_directory = #{working_directory}/run
process_file_path = #{runtime_directory}/#{name}.pid

After calling prefork, the working directory is expanded to a full path and should not be changed.

WEBRick Server

Some servers must run on the main process thread. In this case, the normal interrupt mechanism won't be used and we will handle signals directly.

Create a file for your daemon, e.g. daemon.rb:

#!/usr/bin/env ruby

require 'process/daemon'

# Very simple XMLRPC daemon
class XMLRPCDaemon < Process::Daemon
    def startup
        @rpc_server = WEBrick::HTTPServer.new(
            :Port => 31337,
            :BindAddress => "0.0.0.0"
        )

        @listener = XMLRPC::WEBrickServlet.new

        @listener.add_handler("fourty-two") do |amount|
            "Hello World"
        end

        @rpc_server.mount("/RPC2", @listener)
    end

    def run
        # This is the correct way to cleanly shutdown the server:
        trap(:INT) do
            @rpc_server.shutdown
        end

        @rpc_server.start
    ensure
        @rpc_server.shutdown
    end
end

XMLRPCDaemon.daemonize

Then run daemon.rb start. To stop the daemon, run daemon.rb stop.

Celluloid Actor

Process::Daemon is the perfect place to spawn your celluloid actors.

require 'celluloid'
require 'process/daemon'

class MyActor
    include Celluloid::Actor

    def long_running
        sleep 1000
    end
end

class MyDaemon < Process::Daemon
    def startup
        @actor = MyActor.new

        @actor.async.long_running_process
    end

    def shutdown
        @actor.terminate
    end
end

MyDaemon.daemonize

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request

License

Released under the MIT license.

Copyright, 2015, by Samuel G. D. Williams.

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.