WEBrick's server.rb contains a return that should be a break
Commit 46253 (git hash 6f226d9) added the ability to shut down the running WEBrick server more gracefully, by monitoring a shutdown pipe. However, the logic to actually escape the server loop was written to use "return" instead of break", which causes a LocalJumpError when run inside a threaded server:
LocalJumpError: unexpected return
It is not entirely clear why this does not show up for MRI running the same tests (JRuby master is now running MRI trunk stdlib and tests), but we believe this return should be a "break". A break here exits the server loop and allows the rest of the server logic to finish gracefully without an error bubbling out.
We have made this change in JRuby here: https://github.com/jruby/jruby/commit/ce7e292dcc899111a908467f90fd0c639cfbba18
I am marking this urgent, because MRI 2.2 is almost done, and JRuby plans to release shortly after with expected 2.2 compatibility.
Assigning to akr because he did the original commit.