Since Puma 5.0 (puma/puma@05936689c8),
Puma will automatically set `workers` to `ENV["WEB_CONCURRENCY"] || 0`.
Additionally, if `ENV["WEB_CONCURRENCY"]` > 1, Puma will automatically
set `preload_app`.
This can lead to confusing scenarios for users who are unaware of this
behavior and have customized `config/puma.rb`. For example, if a user
uncomments the `workers` and `preload_app!` directives, it is clear that
Puma will preload the app, and the number of workers can be configured
by setting `ENV["WEB_CONCURRENCY"]`. If the user sets
`ENV["WEB_CONCURRENCY"]` > 1, but then changes their mind and removes
the `workers` or `preload_app!` directives *without* clearing
`ENV["WEB_CONCURRENCY"]`, Puma will still preload the app and launch
`ENV["WEB_CONCURRENCY"]` number of workers. Similarly, if a user
uncomments *only* the `workers` directive and sets
`ENV["WEB_CONCURRENCY"]` > 1, Puma will preload the app even though the
`preload_app!` directive is still commented out.
To avoid such scenarios, this commit removes the commented-out `workers`
and `preload_app!` directives from the default `config/puma.rb`.
Also, to improve discoverability of available configuration options,
this commit adds a link to the Puma DSL documentation at the top of the
file.
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