Ruby apps now have `PUMA_PERSISTENT_TIMEOUT=95` set by default
Change effective on 09 September 2025
All Ruby applications now have PUMA_PERSISTENT_TIMEOUT environment variable set to a default value of 95.
Puma 7.0 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+ 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 }))
Other web server users can use this as a stable interface to retrieve a suggested idle timeout setting.
Update: This setting is only applied automatically for Fir generation. For Cedar generation applications, it is only applied for Rack apps (but not Rails). There’s also an issue with this setting that is fixed in Puma 7.0.3. Please update to Puma 7.0.3, and this behavior will be applied to Rails apps shortly.