Suddenly, after an automatic platform update to version 3.1.2, I get this message in the puma log repeatedly and constantly:
Early termination of worker
+ Gemfile in context: /var/app/current/Gemfile
But the log won't show what the actual error is.
In summary, I fixed this error by adding this in my Gemfile
gem 'nio4r', '2.5.3'
and then running bundle update, pushing code and re-deploying my app.
I share a more detailed explanation into how I got to the solution in this stack overflow answer
