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Description
Expected
Puma to shut down after 5 seconds of inactivity.
# puma.rb
#
# ... rest of file
#
# workers ENV.fetch("WEB_CONCURRENCY") { 2 }
bundle exec puma hello.ru --idle-timeout=5
➜ git:(main) ✗ bundle exec puma hello.ru --idle-timeout=5
Puma starting in single mode...
* Puma version: 6.4.0 (ruby 3.2.0-p0) ("The Eagle of Durango")
* Min threads: 5
* Max threads: 5
* Environment: development
* PID: 23471
* Listening on http://0.0.0.0:3000
Use Ctrl-C to stop
- Gracefully stopping, waiting for requests to finish
=== puma shutdown: 2023-09-21 13:14:34 -0700 ===
- Goodbye!
Actual
Puma restarts workers infinitely.
# puma.rb
#
# ... rest of file
#
workers ENV.fetch("WEB_CONCURRENCY") { 2 }
bundle exec puma hello.ru --idle-timeout=5
➜ git:(main) ✗ bundle exec puma hello.ru --idle-timeout=5
[23279] Puma starting in cluster mode...
[23279] * Puma version: 6.4.0 (ruby 3.2.0-p0) ("The Eagle of Durango")
[23279] * Min threads: 5
[23279] * Max threads: 5
[23279] * Environment: development
[23279] * Master PID: 23279
[23279] * Workers: 2
[23279] * Restarts: (✔) hot (✔) phased
[23279] * Listening on http://0.0.0.0:3000
[23279] Use Ctrl-C to stop
[23279] - Worker 0 (PID: 23405) booted in 0.0s, phase: 0
[23279] - Worker 1 (PID: 23406) booted in 0.0s, phase: 0
[23279] - Worker 0 (PID: 23412) booted in 0.0s, phase: 0
[23279] - Worker 1 (PID: 23411) booted in 0.01s, phase: 0
[23279] - Worker 0 (PID: 23417) booted in 0.01s, phase: 0
[23279] - Worker 1 (PID: 23418) booted in 0.0s, phase: 0
Puma config:
Default Puma config when initializing a Rails app.
# Puma can serve each request in a thread from an internal thread pool.
# The `threads` method setting takes two numbers: a minimum and maximum.
# Any libraries that use thread pools should be configured to match
# the maximum value specified for Puma. Default is set to 5 threads for minimum
# and maximum; this matches the default thread size of Active Record.
#
max_threads_count = ENV.fetch("RAILS_MAX_THREADS") { 5 }
min_threads_count = ENV.fetch("RAILS_MIN_THREADS") { max_threads_count }
threads min_threads_count, max_threads_count
# Specifies the `worker_timeout` threshold that Puma will use to wait before
# terminating a worker in development environments.
#
worker_timeout 3600 if ENV.fetch("RAILS_ENV", "development") == "development"
# Specifies the `port` that Puma will listen on to receive requests; default is 3000.
#
port ENV.fetch("PORT") { 3000 }
# Specifies the `environment` that Puma will run in.
#
environment ENV.fetch("RAILS_ENV") { "development" }
# Specifies the `pidfile` that Puma will use.
pidfile ENV.fetch("PIDFILE") { "tmp/pids/server.pid" }
# Specifies the number of `workers` to boot in clustered mode.
# Workers are forked web server processes. If using threads and workers together
# the concurrency of the application would be max `threads` * `workers`.
# Workers do not work on JRuby or Windows (both of which do not support
# processes).
#
workers ENV.fetch("WEB_CONCURRENCY") { 2 }
# Use the `preload_app!` method when specifying a `workers` number.
# This directive tells Puma to first boot the application and load code
# before forking the application. This takes advantage of Copy On Write
# process behavior so workers use less memory.
#
# preload_app!
# Allow puma to be restarted by `bin/rails restart` command.
plugin :tmp_restart
To Reproduce
hello.ru
file:
run lambda { |env| [200, {"Content-Type" => "text/plain"}, ["Hello World"]] }
Run it with:
bundle exec puma hello.ru --idle-timeout=5
Notes
I initially thought this was because of Scout APM's Puma worker loop, because I was seeing this when also enabling preload_app
and using scout_apm
: (on a new Rails app, which you can clone here):
➜ git:(main) ✗ RAILS_ENV=production SCOUT_DEV_TRACE=true bundle exec puma --idle-timeout=5
[24120] Puma starting in cluster mode...
[24120] * Puma version: 6.4.0 (ruby 3.2.0-p0) ("The Eagle of Durango")
[24120] * Min threads: 5
[24120] * Max threads: 5
[24120] * Environment: production
[24120] * Master PID: 24120
[24120] * Workers: 2
[24120] * Restarts: (✔) hot (✖) phased
[24120] * Preloading application
[24120] * Listening on http://0.0.0.0:3000
[24120] Use Ctrl-C to stop
I, [2023-09-21T13:20:03.516036 #24245] INFO -- : Installing Puma worker loop.
[24120] - Worker 0 (PID: 24245) booted in 0.0s, phase: 0
I, [2023-09-21T13:20:03.517641 #24246] INFO -- : Installing Puma worker loop.
[24120] - Worker 1 (PID: 24246) booted in 0.0s, phase: 0
I, [2023-09-21T13:20:08.541142 #24249] INFO -- : Installing Puma worker loop.
[24120] - Worker 1 (PID: 24249) booted in 0.0s, phase: 0
I, [2023-09-21T13:20:08.541951 #24250] INFO -- : Installing Puma worker loop.
[24120] - Worker 0 (PID: 24250) booted in 0.0s, phase: 0
However, looks like Scout APM will detect when shutting down, so the real culprit is the workers
option not allowing Puma to shut down.
Versions
Desktop (please complete the following information):
- OS: MacOS Monterrey 12.6
- Puma Version 6.4.0