Rails apps now have `PUMA_PERSISTENT_TIMEOUT=95` set by default
Change effective on 29 September 2025
Previously, this setting was only applied to Rack applications. With this change, all Ruby applications now have the PUMA_PERSISTENT_TIMEOUT environment variable set to a default value of 95.
Puma 7.0.3+ introduced the ability to configure the persistent_timeout value via an environment variable. Router 2.0 uses an idle timeout value of 90s https://devcenter.heroku.com/articles/http-routing#keepalives. To avoid a situation where a request is sent right before Puma closes the connection, the value needs to be slightly higher than the Router’s value.
Applications that are not on Puma 7.0.3+ can use it manually in their config/puma.rb file:
# config/puma.rb
# Only required for Puma 6 and below
persistent_timeout(ENV.fetch("PUMA_PERSISTENT_TIMEOUT") { 95 }.to_i)
Other web server users can use this as a stable interface to retrieve a suggested idle timeout setting.