ioquatix/process-daemon

# Process::Daemon

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

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## 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](https://celluloid.io) 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](http://www.codeotaku.com/samuel-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.