til/rails/restart-puma-server-by-touching-restart-file.md

Restart Puma Server By Touching Restart File

Puma includes a plugin that allows us to restart the web server by touching the tmp/restart.txt file.

In one terminal pane I have my Rails server running. In another terminal pane from the Rails directory, where there exists a tmp folder, I run the following command.

$ touch tmp/restart.txt

Then in the pane running the Rails server, I see the following after a second:

* Restarting...
=> Booting Puma
=> Rails 8.0.1 application starting in development
...

What is happening is that touch updates the modified time of that file, which already exists in the temp directory. When the plugin notices (it checks every 2 seconds) that the modified time is now fresher than the original modified time when the plugin started, then it calls launcher.restart.

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