Invoke delayed_job capistrano tasks only on specific servers

Question

I have a dedicated server for delayed_job tasks. I want to start, stop, and restart delayed_job workers on only this server. I am using the capistrano recipes provided by delayed_job.

When I only had 1 server, this was my config:

before "deploy:restart", "delayed_job:stop"
after  "deploy:restart", "delayed_job:start"

after "deploy:stop",    "delayed_job:stop"
after "deploy:start",   "delayed_job:start"

Now I want to have those hooks only apply to a separate delayed_job server (role :delayed_job <ip address>). Is this possible to do elegantly? Do I have to wrap each delayed_job tasks in a meta task? Or write my own tasks and not use the ones provided by delayed job?

Answer 1

When you define a task in Capistrano you can restrict the execution of the task to specific role(s). The way you do this is by passing the :role option.

It seems the default delayed_job Capistrano recipe does this.

desc "Stop the delayed_job process"
task :stop, :roles => lambda { roles } do
  run "cd #{current_path};#{rails_env} script/delayed_job stop"
end

According to the source code, the task fetches the list of roles from the :delayed_job_server_role configuration variable.

Back to your problem, to narrow the execution of the tasks to a specific group of servers, define a new role (for example worker) in your deploy.rb

role :worker, "192.168.1.1" # Assign the IP of your machine

Then set the :delayed_job_server_role to that name

set :delayed_job_server_role, :worker

That's all. Now the tasks will be executed, but only to the servers listed in the :worker role.