Unicorn PID is stale on initial deploy

Question

I'm trying to use capistrano and unicorn for the first time in my rails application. I can deploy successfully except unicorn won't start with the following error from stderr: ``` I, [2013-03-25T16:55:35.877323 #2378] INFO -- : reloading config_file=/var/www/good/current/config/unicorn.rb E, [2013-03-25T16:55:35.881496 #2378] ERROR -- : error reloading config_file=/var/www/good/current/config/unicorn.rb: Already running on PID:2378 (or pid=/var/www/good/current/tmp/pids/unicorn.pid is stale) (ArgumentError) E, [2013-03-25T16:55:35.881548 #2378] ERROR -- : /var/www/good/shared/bundle/ruby/1.9.1/gems/unicorn-4.6.2/lib/unicorn/http_server.rb:193:in `pid=' E, [2013-03-25T16:55:35.881579 #2378] ERROR -- : /var/www/good/shared/bundle/ruby/1.9.1/gems/unicorn-4.6.2/lib/unicorn/configurator.rb:111:in `block in commit!' E, [2013-03-25T16:55:35.881606 #2378] ERROR -- : /var/www/good/shared/bundle/ruby/1.9.1/gems/unicorn-4.6.2/lib/unicorn/configurator.rb:108:in `each' E, [2013-03-25T16:55:35.8816…

Accepted Answer

Your problem is when you're deploying you aren't probably killing the unicorn master pid before you run unicorn again. I think the problem is in your capistrano recipe...

With unicorn we usually save the pid in a shared folder in production environment when we start the server, where you save also the logs, uploads and other sfuff that is independent of each environment.

see this two tasks of one of my deploy.rb:

```
desc "Start unicorn"
  task :start, :except => { :no_release => true } do
    run "cd #{current_path} ; bundle exec unicorn_rails -c config/unicorn.rb -D"
    run "ps aux | grep unicorn_rails | head -n 1 | awk '{print $2}' > #{deploy_to}/shared/tmp/pids/unicorn.pid"
  end

desc "Stop unicorn"
  task :stop, :except => { :no_release => true } do
    run "kill -s QUIT `cat  #{deploy_to}/shared/tmp/pids/unicorn.pid`"
  end
```

so when i stop unicorn i always kill the master pid that is in the shared folder and when i start it, i make a copy of this pid to a shared folder in the production project. In this case, my restart task is calling first the stop and then the start, but this isn't zero down time...

The following link have a recipe with zero down time if want to give a try: https://github.com/railscasts/373-zero-downtime-deployment/blob/master/blog-after/config/recipes/templates/unicorn.rb.erb

Unicorn PID is stale on initial deploy

Solution

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