ActiveRecord::ConnectionTimeoutError: could not obtain a database connection within 5.000 seconds (waited 5.000 seconds)

Question

I have a rails app in production that i deployed some changes to the other day. All of a sudden now I get the error ActiveRecord::ConnectionTimeoutError: could not obt

Answer 1

I had the same problems which were caused by too many open connections to the database. This can happen when you have database queries outside of a controller (in a model, mailer, pdf generator, ...).

I could fix it by wrapping those queries in this block which closes the connection automatically.

ActiveRecord::Base.connection_pool.with_connection do
  # your code
end

Since Puma works multi-threaded, the pool size (as eabraham mentioned) can be a limitation, too. Try to increase it (a little)...

I hope this helps!