Using puma on Heroku with Rails 3.2.22.2 and Ruby 2.2, not threadsafe? What is the point?

Question

I've deployed a rails app 3.2.22.2 running on ruby 2.2.0p0 on heroku with puma as web server.

Heroku loves puma and advice new apps to use it:

https://devcenter.heroku.com/articles/deploying-rails-applications-with-the-puma-web-server

Puma uses threads, in addition to worker processes, to make more use of available CPU. You can only utilize threads in Puma if your entire code-base is thread safe. Otherwise, you can still use Puma, but must only scale out through worker processes.

I can't ensure my rails app (my code in fact) and the gems are threadsafe, so my only option is to add some workers and configure my Procfile like this:

web: bundle exec puma -t 1:1 -p ${PORT:-3000} -e ${RACK_ENV:-development}
worker: bundle exec rake jobs:work

Just in case, I've also set the config vars as:

=== myapp-staging Config Vars
DATABASE_URL:          postgres://this:that@addresse:port/more
LANG:                  en_US.UTF-8
MIN_THREADS:           1
NEW_RELIC_LICENSE_KEY: key
NEW_RELIC_LOG:         stdout
PAPERTRAIL_API_TOKEN:  key
RACK_ENV:              staging
RAILS_ENV:             staging
RAILS_MAX_THREADS:     1
SENSIBLE_DEFAULTS:     enabled
WEBSOLR_URL:           https://index.websolr.com/solr/index
WEB_CONCURRENCY:       1

So... if I can only use only 1 thread, is puma the right solution for my app?

Thank you!

ps: please have a look at that question What configuration for Rails 3.2.22.2 + Puma + Heroku?

fro_oo fro_oo · Accepted Answer · 2016-05-06T13:58:06

There's no point using puma on a rails app not threadsafe (version < 4.x), but to handle the slow clients problem.

Besides that, the only choice is to set the web concurrency to 1.

Using puma on Heroku with Rails 3.2.22.2 and Ruby 2.2, not threadsafe? What is the point?

1 Answers