execute a task serially on different hosts, not in parallel

stephen.judkins (stephen judkins) — Wed, 18 Apr 2007 19:37:06 GMT

// This code will let you define a task, using the same conventions as Capistrano's "task", that executes serially on the hosts defined by its role rather than in parallel. This is useful if you are deploying to multiple live servers behind a load balancer, the deployment process takes down the server, and you want only one server down at a given time.

This efinitely uses magic. we're not sure if this will work in future versions of Capistrano, but changing it should be relatively simple.



def serial_task(name, options = {}, &block)

  servers = self.roles[options[:roles]].collect {|server| server.host}

  task_syms = []

  servers.each do |hostname|

    role_sym = "_serial_task_#{name.to_s}_#{hostname}".to_sym

    task_sym = "_do_task_#{name.to_s}_#{hostname}".to_sym

    task_syms << task_sym

    role role_sym, hostname

    task task_sym, :roles => role_sym, &block

  end

  task name do

    task_syms.each do |t|

      self.send t

    end

  end

end

Here is an example. Note the syntax is just the same as Capistrano's "task".



serial_task :pwd, :roles => web do

  run "pwd"

end

Deploy script for rails applications under version control

tobi (Tobias Luetke) — Thu, 07 Apr 2005 09:42:10 GMT

#!/usr/bin/env ruby



require 'yaml'

require 'rubygems'

require_gem 'net-ssh'



$stdout.sync = true



def help

  puts <<-USAGE

This tool allows you to conviniently deploy your projects on production

or staging servers.



  Useage:

    deploy 

    Please specify configuration in ~/.deployrc

    

  Example:  

    

    example ~/.deployrc:   

    

      hieraki:

        server: linux

        get: svn export svn://myserver/hieraki/trunk

        directory: /var/www/applications/hieraki

        test: RAILS_ENV=production rake



        after_test:

          - chmod 777 log/

          - chmod 666 log/*



        after_commit:

          - sudo /etc/init.d/apache reload    



  Note: 

  

    server, get and directory are required

    

    available hooks are

      - after_connect

      - after_deploy

      - after_test

      - after_commit

        

  USAGE

  exit

end



def do_exec(cmd)

  print "\n\n  #{cmd}\n    "

  

  stderr = ""

  $session.process.open( cmd ) do |cmd|

    cmd.on_exit do |p, status|

      if status == 0

        print "[done]\n" 

      else

        puts "    #{stderr}"        

        print "[failed]\n" 

        exit

      end

    end

    

    cmd.on_stderr do |p, data|

      stderr << data.gsub(/\n/, "\n    ")

    end    

    cmd.on_stdout do |p, data|

      STDOUT << data.gsub(/\n/, "\n    ")

    end                

  end  

end



# Batch jobs



def deploy

  puts      "\ndeploying"  



  print     "  creating dirs"

  do_exec   "mkdir -p #{$config['directory']}" 



  print     "  get"

  do_exec   "#{$config['get']} #{$config['deploy']}"

end



def test

  puts      "\ntesting"  

  do_exec   "cd #{$config['deploy']}; #{$config['test']}"

end



def commit

  puts      "\ncomitting"

  print     "  creating new link"

  do_exec   "ln -nfs #{$config['deploy']}/ #{$config['target']}"

end



def run_tasks(tasks)

  $config[tasks].to_a.each do |task|    

    do_exec "cd #{$config['deploy']}; #{task}" 

  end

end





app_name = ARGV[0] || help

$config = YAML::load(File.open(File.expand_path("~/.deployrc")))[app_name]



# compute deploy directory 

$config['deploy'] = $config['directory'] + "/#{Time.now.strftime("%Y%m%d-%H%M")}"

# compute target directory 

$config['target'] = $config['directory'] + "/latest"



puts "deploying #{app_name} to #{$config["server"]}"



$session = Net::SSH.start( $config["server"] )



run_tasks("after_connect")  

deploy

run_tasks("after_deploy")

test

run_tasks("after_test")

commit

run_tasks("after_commit")

puts ""

puts "success!"

DZone Snippets: deploy code

execute a task serially on different hosts, not in parallel

Deploy script for rails applications under version control