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https://github.com/Growstuff/growstuff.git
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Brenda Wallace
8995037a86
Puma was running in cluster mode with one worker, which keeps a master process holding a full copy of the preloaded app next to the worker. Heroku counts both, so the 512 MB dyno sat at ~620 MB with a constant R14. WEB_CONCURRENCY of 0 or 1 now runs one process with no master; two or more workers still use cluster mode with preload_app!. Puma reads WEB_CONCURRENCY itself, so single mode is set explicitly with `workers 0`. Added a comment explaining the memory budget.
62 lines
2.6 KiB
Ruby
62 lines
2.6 KiB
Ruby
# frozen_string_literal: true
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# Puma can serve each request in a thread from an internal thread pool.
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# The `threads` method setting takes two numbers: a minimum and maximum.
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# Any libraries that use thread pools should be configured to match
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# the maximum value specified for Puma. Default is set to 5 threads for minimum
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# and maximum; this matches the default thread size of Active Record.
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#
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max_threads_count = ENV.fetch("RAILS_MAX_THREADS") { 5 }
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min_threads_count = ENV.fetch("RAILS_MIN_THREADS") { max_threads_count }
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threads min_threads_count, max_threads_count
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# Specifies the `port` that Puma will listen on to receive requests; default is 3000.
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#
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port ENV.fetch("PORT") { 3000 }
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# Specifies the `environment` that Puma will run in.
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#
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environment ENV.fetch("RAILS_ENV") { "development" }
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# Specifies the `pidfile` that Puma will use.
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pidfile ENV.fetch("PIDFILE") { "tmp/pids/server.pid" }
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# Specifies the number of `workers` to boot in clustered mode.
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# Workers are forked web server processes. If using threads and workers together
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# the concurrency of the application would be max `threads` * `workers`.
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# Workers do not work on JRuby or Windows (both of which do not support
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# processes).
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#
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# MEMORY BUDGET: production is a 512 MB Heroku Basic dyno. Heroku raises R14 at
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# 512 MB and kills the dyno at ~1 GB (R15), so aim to keep the whole dyno below
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# 500 MB. Heroku sums the RSS of every process in the dyno, and each Ruby
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# process running this app costs roughly 200-300 MB, so the number of
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# processes is the main lever:
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#
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# * Clustered mode with a single worker runs a master that holds a full copy
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# of the preloaded app next to the worker, and both are counted. That was
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# ~620 MB, permanently over quota.
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# * So 0 or 1 means single mode: one process, no master. Concurrency comes
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# from the threads (RAILS_MAX_THREADS), which are cheap compared to
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# processes.
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# * Two or more workers will not fit in 512 MB. Only raise WEB_CONCURRENCY
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# above 1 after moving to a bigger dyno, and check `heroku logs` for R14
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# afterwards.
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#
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web_concurrency = Integer(ENV.fetch("WEB_CONCURRENCY") { 0 })
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# Puma reads WEB_CONCURRENCY itself, so single mode has to be set explicitly.
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workers(web_concurrency > 1 ? web_concurrency : 0)
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if web_concurrency > 1
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# Use the `preload_app!` method when specifying a `workers` number.
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# This directive tells Puma to first boot the application and load code
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# before forking the application. This takes advantage of Copy On Write
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# process behavior so workers use less memory.
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#
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preload_app!
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end
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# Allow puma to be restarted by `rails restart` command.
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plugin :tmp_restart
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