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Running and Restarting a Rails Puma Webserver in Production

Let’s dive into how to run a Rails Puma webserver process and how to restart it.

As you may be aware, Puma is the default webserver for Rails. Running the webserver locally is simple (bin/rails s). Running Puma on a production webserver is not so easy and there are a few considerations:

  1. You’ll want to run Rails in production mode
  2. You’ll want to run Puma as a continuous background process

Here’s how we run Puma on our webservers:

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RAILS_ENV=production bundle exec puma --daemon --bind unix://tmp/sockets/puma.sock --state tmp/sockets/puma.state --control unix://tmp/sockets/pumactl.sock

Let’s break it down.

  • RAILS_ENV=production - An environment variable that tells rails to run the server in production mode.
  • bundle exec puma --daemon - Runs Puma as a daemonized background process
  • --bind unix://tmp/sockets/puma.sock - Specifies the location of the puma socket file.
  • --state tmp/sockets/puma.state - Specifies the location of the state file. It stores Puma’s PID, as well as control url & auth_token, which are required for restarting
  • --control unix://tmp/sockets/pumactl.sock - Specifies a separate socket location for pumactl. Required for restarting

To restart Puma, you can use pumactl. This command allows you to interact with a running Puma server. You just need to specify the state file and pass the restart param:

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bundle exec pumactl --state tmp/sockets/puma.state restart