title: Puma not creating socket at defined location when started with `rails server`
body: <p>I'm deploying my Rails app using nginx, puma, and capistrano. It's deployed by a user called <code>deploy</code> and the deploy location is under the home directory (<code>/home/deploy</code>)</p>
  
  <p>I have Puma configured to create a socket under the <code>shared</code> folder that Capistrano symlinks all it's releases to. Correspondingly, nginx is configured to look at that socket as well (see config files below)</p>
  
  <p>However when I start up the Rails / Puma webserver - </p>
  
  <pre><code>cd /home/deploy/my_app/current
  SECRET_KEY_BASE=.... DATABASE_PASSWORD=... rails s -e production
  </code></pre>
  
  <p>I notice that no socket file is created. When I visit the site in my browser and then look at the Nginx error log, it is also complaining about that socket not existing. </p>
  
  <pre><code>2016/07/17 14:26:19 [crit] 26055#26055: *12 connect() to unix:/home/deploy/my_app/shared/tmp/sockets/puma.sock failed (2: No such file or directory) while connecting to upstream, client: XX.YY.XX.YY, server: localhost, request: "GET http://testp4.pospr.waw.pl/testproxy.php HTTP/1.1", upstream: "http://unix:/home/deploy/my_app/shared/tmp/sockets/puma.sock:/500.html", host: "testp4.pospr.waw.pl"
  </code></pre>
  
  <p>How do I go about getting puma to create that socket? </p>
  
  <p>Thanks!</p>
  
  <h1>Puma Config</h1>
  
  <pre><code># config/puma.rb
  
  ...
  
  # `shared_dir` is the symlinked `shared/` directory created
  # by Capistrano - `/home/deploy/my_app/shared`
  
  # Set up socket location
  bind "unix://#{shared_dir}/tmp/sockets/puma.sock"
  
  # Logging
  stdout_redirect "#{shared_dir}/log/puma.stdout.log", "#{shared_dir}/log/puma.stderr.log", true
  
  # Set master PID and state locations
  pidfile "#{shared_dir}/tmp/pids/puma.pid"
  state_path "#{shared_dir}/tmp/pids/puma.state"
  activate_control_app
  
  ...
  </code></pre>
  
  <h1>Nginx sites config</h1>
  
  <pre><code># /etc/nginx/sites-available/default
  
  upstream app {
      # Path to Puma SOCK file
      server unix:/home/deploy/my_app/shared/tmp/sockets/puma.sock fail_timeout=0;
  }
  
  server {
      listen 80;
      server_name localhost;
  
      root /home/deploy/my_app/public;
  
      try_files $uri/index.html $uri @app;
  
      location @app {
          proxy_pass http://app;
          proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
          proxy_set_header Host $http_host;
          proxy_redirect off;
      }
  
      error_page 500 502 503 504 /500.html;
      client_max_body_size 4G;
      keepalive_timeout 10;
  }
  </code></pre>