Creating a Windows service

For this I used Daniel Berger’s win32-service package. This is a great package that does literally everything for you to enable you to create a nice Windows service. Just install the gem like this:

gem install win32-service

I used examples/daemon_test.rb as the base template to make my Windows Service. This piece of code contains all that is needed to run the code snippet above as a service. In this file you will find a class called Daemon that has a number of methods necessary for running a Windows service. Put in the necessary requires and place your ActiveRecord initialization code at the beginning of the code. Then under service_main, while the status == RUNNING, put in the main processing code, minus the loop. Your code could possibly look something like this (don’t cut and paste this code, just use it as a reference):

require 'rubygems'
require 'logger'
require 'active_record'
require 'c:/myrailsapp/app/models/message' # remember to put in the absolute path here
require "win32/service"
include Win32

ActiveRecord::Base.establish_connection({
:adapter  => "mysql",
:host     => "localhost",
:username => "xxx",
:password => "xxx",
:database => "mydatabase"
})

# I start the service name with an 'A' so that it appears at the top
SERVICE_NAME = "MyProcess Service"
SERVICE_DISPLAYNAME = "MyProcess"

if ARGV[0] == "install"
svc = Service.new
svc.create_service{ |s|
s.service_name = SERVICE_NAME
s.display_name = SERVICE_DISPLAYNAME
s.binary_path_name = 'ruby ' + File.expand_path($0)
s.dependencies = []
}
svc.close
puts "installed"
elsif ARGV[0] == "start"
Service.start(SERVICE_NAME)
# do stuff before starting
puts "Ok, started"
elsif ARGV[0] == "stop"
Service.stop(SERVICE_NAME)
# do stuff before stopping
puts "Ok, stopped"
elsif ARGV[0] == "uninstall" || ARGV[0] == "delete"
begin
Service.stop(SERVICE_NAME)
rescue
end
Service.delete(SERVICE_NAME)
# do stuff before deleting
puts "deleted"
elsif ARGV[0] == "pause"
Service.pause(SERVICE_NAME)
# do stuff before pausing
puts "Ok, paused"
elsif ARGV[0] == "resume"
Service.resume(SERVICE_NAME)
# do stuff before resuming
puts "Ok, resumed"
else

if ENV["HOMEDRIVE"]!=nil
puts "No option provided.  You must provide an option.  Exiting..."
exit
end

## SERVICE BODY START
class Daemon
logger = Logger.new("c:/myprocess.log")

def service_stop
logger.info "Service stopped"
end

def service_pause
logger.info "Service paused"
end

def service_resume
logger.info "Service resumed"
end

def service_init
logger.info "Service initializing"
# some initialization code for your process
end

## worker function
def service_main
begin
while state == RUNNING || state == PAUSED
while state == RUNNING

# --- start processing code
messages = Message.find :all,
:conditions => ['sent = (?)', 0], # check if the message has been sent
:limit => 20 # retrieve and process 20 at a time

# array of threads
threads = []

# iterate through each message
for message in messages do
# start a new thread to process the message
threads < < Thread.new(message) do |message|
# process the message here ...
message.sent = 1
message.save
end

# don't finish until all threads are done
threads.each do |t|
begin
# join the threads when it's done
t.join
rescue RuntimeError => e
# do some rescuing
puts “Failed: #{e.message}”
end
end
end

# — end processing code

end
if state == PAUSED
# if you want do something when the process is paused
end
end
rescue StandardError, Interrupt => e
logger.error “Service error : #{e}”
end
end
end

d = Daemon.new
d.mainloop

end #if

Important to note that you need to put in the absolute path in the require as the service wouldn’t be starting at the Rails app.

Now you can install and start the Windows service (assuming the code is written in a file called ‘message_service.rb’:

c:/>ruby message_service.rb install
c:/>ruby messag_service.rb start

You can also control it from your Windows Services MMC console. What you have now is a Windows service that loops around until there is a message record in your database that is not sent (sent = 0). If there are, it will retrieve up to 20 messages at a go and process them with a thread each (parallelizing the processing to make it faster). Once it is processed, it will indicate the meesage has been sent (sent = 1) and loop again. Now you can happily create messages from your Rails app and stuff them into the database, while your message processor will process them separately.