I believe you are in error. There is at least one difference between these two builds.

Passed:

$ gem --version
Picked up _JAVA_OPTIONS: -Xmx2048m -Xms512m
2.7.4

Failed:

$ gem --version
Picked up _JAVA_OPTIONS: -Xmx2048m -Xms512m
2.7.5

And in fact there's a bug we reported in RubyGems 2.7.5 that prevents it from activating updated default gems like minitest, test-unit, rake, and so on: rubygems/rubygems#2188

For this reason we did not ship the latest RubyGems in JRuby 9.1.16.0, but I believe RVM attempts to install the latest regardless. I assume there's a way you can turn that off.

Please confirm that reverting to RubyGems prior to 2.7.5 fixes your issues.

An obvious one (so I doubt it is this) is whether you have no .lock file and Gemfile with open dependencies. Some gem being different could explain this.

As an aside we would love to see 9.0.4.0 be replaced with 9.1.16.0. We have not supported 9.0.x for more than a year.

FWIW the RubyGems issue may eventually come back around to being a JRuby bug, but for now I think the ball's in their court. You may be able to help them investigate, though.

Oh! I missed that. Thanks. Using Rubygems 2.7.4 with JRUBY 9.0.4.0 works. I tried the same with JRuby 9.1.16.0 and I got a travis timeout https://travis-ci.org/rack/rack/jobs/345309660. I guess the test suite entered a deadlock state because there is no output for a while. I'll try to reproduce that locally to see if it is something with the JRuby version or if it is something on travis.

It is passing locally with 9.1.15 but failing on travis ci with some kind of deadlock. Any recommendations how to debug?

@rafaelfranca Hmm I'm not sure. Best way to investigate would be to reproduce that environment locally and try to get a thread dump, or use the Travis docker image to do the same on a local environment. You may be able to figure out what's freezing by adding -v or similar to the test run so we can see where it hangs.

I'm going to call this fixed, but I'm happy to assist figuring out the deadlock.