(cap3) Any documentation on writing capistrano 3 gems for programmatically adding servers during deploy?

[Michael]

Versions:

• Ruby
• 2.0.0
• Capistrano
• 3.0.1

Does any documentation exist for writing capistrano 3 gems for programmatically adding servers during deployment?

I can only find Capistrano 2 gems for doing such tasks.  ( https://github.com/srbartlett/elbow , https://github.com/tverbiscer/capistrano-asgroup )

I'm currently testing this:   (The below is a useless example, but should try to add '127.0.0.1' to the list of servers...)

root@domU-example:/var/lib/gems/2.0.0/gems/capistrano-autoscale-0.0.1/lib/capistrano# cat autoscale.rb

require 'aws-sdk'

require 'net/dns'

####  The below is old Cap2 syntax...  What is the new equivalent? ####

#Capistrano::Configuration.instance(:must_exist).load do

### end old syntax (I think) ####

module Capistrano

class Configuration

module ELB

def elastic_load_balancer(name, *args)

hostname = "127.0.0.1"

server(hostname, *args)

end

end

include ELB

end

end

This just fails with this:

root@domU-example:~/webapp# cap production deploy --trace

** Invoke production (first_time)

** Execute production

** Invoke load:defaults (first_time)

** Execute load:defaults

cap aborted!

undefined method `elastic_load_balancer' for main:Object

config/deploy/production.rb:14:in `<top (required)>'

/var/lib/gems/2.0.0/gems/capistrano-3.0.1/lib/capistrano/setup.rb:13:in `load'

/var/lib/gems/2.0.0/gems/capistrano-3.0.1/lib/capistrano/setup.rb:13:in `block (2 levels) in <top (required)>'

/var/lib/gems/2.0.0/gems/rake-10.1.1/lib/rake/task.rb:236:in `call'

/var/lib/gems/2.0.0/gems/rake-10.1.1/lib/rake/task.rb:236:in `block in execute'

/var/lib/gems/2.0.0/gems/rake-10.1.1/lib/rake/task.rb:231:in `each'

/var/lib/gems/2.0.0/gems/rake-10.1.1/lib/rake/task.rb:231:in `execute'

/var/lib/gems/2.0.0/gems/rake-10.1.1/lib/rake/task.rb:175:in `block in invoke_with_call_chain'

/usr/lib/ruby/2.0.0/monitor.rb:211:in `mon_synchronize'

/var/lib/gems/2.0.0/gems/rake-10.1.1/lib/rake/task.rb:168:in `invoke_with_call_chain'

/var/lib/gems/2.0.0/gems/rake-10.1.1/lib/rake/task.rb:161:in `invoke'

/var/lib/gems/2.0.0/gems/rake-10.1.1/lib/rake/application.rb:149:in `invoke_task'

/var/lib/gems/2.0.0/gems/rake-10.1.1/lib/rake/application.rb:106:in `block (2 levels) in top_level'

/var/lib/gems/2.0.0/gems/rake-10.1.1/lib/rake/application.rb:106:in `each'

/var/lib/gems/2.0.0/gems/rake-10.1.1/lib/rake/application.rb:106:in `block in top_level'

/var/lib/gems/2.0.0/gems/rake-10.1.1/lib/rake/application.rb:115:in `run_with_threads'

/var/lib/gems/2.0.0/gems/rake-10.1.1/lib/rake/application.rb:100:in `top_level'

/var/lib/gems/2.0.0/gems/rake-10.1.1/lib/rake/application.rb:78:in `block in run'

/var/lib/gems/2.0.0/gems/rake-10.1.1/lib/rake/application.rb:165:in `standard_exception_handling'

/var/lib/gems/2.0.0/gems/rake-10.1.1/lib/rake/application.rb:75:in `run'

/var/lib/gems/2.0.0/gems/capistrano-3.0.1/lib/capistrano/application.rb:12:in `run'

/var/lib/gems/2.0.0/gems/capistrano-3.0.1/bin/cap:3:in `<top (required)>'

/usr/local/bin/cap:23:in `load'

/usr/local/bin/cap:23:in `<main>'

Tasks: TOP => production

Files:

• Capfile

root@domU-example:~/webapp# cat Capfile  | grep -v "^#"

require 'capistrano/setup'

require 'capistrano/deploy'

require 'capistrano/bundler'

require 'capistrano/rails/assets'

require 'capistrano/rails/migrations'

Dir.glob('lib/capistrano/tasks/*.cap').each { |r| import r }

• deploy.rb

root@dom-example:~/webapp# cat config/deploy.rb  | grep -v "^#" | grep -v "^$"

set :application, 'blog'

set :ssh_options, {:forward_agent => false, keys: ['/home/deploy/.ssh/private_key'], :paranoid => false}

set :deploy_via, :remote_cache

set :use_sudo, true

set :deploy_to, '/webapp'

set :scm, :git

set :scm_user, :git

namespace :deploy do

  desc 'Restart application'

  task :restart do

    on roles(:app), in: :sequence, wait: 5 do

      # Your restart mechanism here, for example:

      if test("[ ! -d " + release_path.join("tmp").to_s + " ]")

        execute "mkdir ", release_path.join("tmp")

      end

      execute :touch, release_path.join('tmp/restart.txt')

    end

  end

  after :restart, :clear_cache do

    on roles(:web), in: :groups, limit: 3, wait: 10 do

      # Here we can do anything such as:

      # within release_path do

      #   execute :rake, 'cache:clear'

      # end

    end

  end

  after :finishing, 'deploy:cleanup'

end

• Stage files (production.rb, staging.rb)

root@domU-example:~/webapp/config/deploy/# cat production.rb  | grep -v "^#" 

require 'capistrano/autoscale'

set :rails_env, "production"

set :stage, :production

set :user, 'deploy'

elastic_load_balancer "example-elb.example.com", :web

Any pointers in the right direction would be greatly appreciated.  I've no issues reading as much documentation as you send me, but I haven't found this one yet....

-- Michael

[Lee Hambley]

I can't see the value of the elastic_load_balancer function, if all it does it call server.

You haven't included your module into the main scope, you have included it into Capistrano::Configuration, where it should, if anywhere be in Capistrano::DSL.

To programatically define servers, just call `server()` from anywhere which has Capistrano::DSL included.

(I think that's right, anyway, I have't ever actually tried, but the top-level stuff like release_path and on() and friends all come from the DSL module being included in to the main scope)

Lee Hambley

--

http://lee.hambley.name/

+49 (0) 170 298 5667

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[Michael]

https://github.com/srbartlett/elbow/pull/3

Thanks Lee.  That was the kick I needed.

[Lee Hambley]

Awesome HTH!

Sent from my Nexus 4.

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