What does Early termination of worker puma log mean and why is it happening?

The problem for my case was a difference in the patch version of the puma that was used.

Gist of it was AWS Elastic Beanstalk was using puma 4.3.3 while I was using puma 4.3.5.

Had to fix the version of puma used in my Gemfile to exactly 4.3.3 to match the stack used by AWS Elastic Beanstalk as of today prevent this error.

More details in this answer of mine here for a similar question.

Ok so this took a lot of debugging and going down a lot of different rabbit holes. The problem was very painfully simple. I created a class which I misspelled and called, GetLitsingsResponse. After changing the class back to GetListingsResponse Puma works just fine in my remote AWS Elastic beanstalk environment. It's very strange out locally on my Mac OS Puma had no problem. But in the 64bit Amazon Linux 2018.03 v2.11.4 running Ruby 2.6 (Puma) platform Puma would not function normally.