When trying to kick off Rack::Servers in different threads, I run into a bit of a weird race condition issue which only happens on Jruby-1.6.7. It seems that the Rack::Server#start calls a trap(:INT) which invokes Kernel#trap to call __jtrap in Jruby land. Only I get a NoMethodError when the RubyKernel#trap calls __jtrap.

I've got a test here which can reproduce (on both linux and OSX) using jdk1.6. Testing in jruby-1.7.0-preview seems to work.

Here is the offending java code RubyKernel#trap.

Simply retrying will eventually 'work' and __jtrap can be found it seems, but retrying until it works seems incorrect. A simple global lock cannot work in this situation as Rack::Server#start doesn't return to return the hold on the lock until end.