How can I prevent R14 errors and swap memory usage in a Rails app on Heroku?

Question

My question:
Is this exemplary of memory bloat, memory leak, or just bad server configuration?

First, I will add a screenshot of memory usage

As you can see, I have been using swap memory.

Also, I am getting a constant plateau and then increase in memory after setting up my Puma server config/puma.rb file according to the Heroku documentation.

I am running the hobby dyno 1x (512 mb) with 0 workers.

My WEB_CONCURRENCY variable is set to 1

My RAILS_MAX_THREADS is also set to 1

MIN_THREADS is also set to 1

Here is my config/puma.rb file

workers Integer(ENV['WEB_CONCURRENCY'] || 2)
threads_count = Integer(ENV['RAILS_MAX_THREADS'] || 5)
threads threads_count, threads_count

preload_app!

rackup      DefaultRackup
port        ENV['PORT']     || 3000
environment ENV['RACK_ENV'] || 'development'

on_worker_boot do
  # Worker specific setup for Rails 4.1+
  ActiveRecord::Base.establish_connection
end

I am using the derailed gem to measure memory use from my gems.

I am using rack-mini-profiler & memory_profiler to measure on a per page basis.

After allowing the app the run, here is the following:

As you can see the app is not going over its limit. If anyone has any suggestions that make sense please feel free to answer the question.

Answer 1

The dyno and puma set up mentioned above is producing this report.

So, we are now only using swap memory occasionally and not more than a few MB and only occasionally hitting 23 MB. The app uses a lot of gems and you can see that we are staying under the 512 MB limit.

I used the following documentation from Heroku:
To get your puma server configured properly
https://devcenter.heroku.com/articles/deploying-rails-applications-with-the-puma-web-server

For R14 memory errors
https://devcenter.heroku.com/articles/ruby-memory-use