jruby-rack-0.9.4.jar doesn't contain rack/lock.rb!!! that's it.

Rack::Lock is just used with some database adapters that's the reason why it just crashes sometimes.

If jruby-rack didn't bundle its own version of Rack this wouldn't be an issue and people could choose whatever version of Rack was suitable for their environment.

http://snapshots.repository.codehaus.org/org/jruby/rack/jruby-rack/0.9.5-SNAPSHOT/jruby-rack-0.9.5-20090625.190033-5.jar

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Having trouble getting into Kenai at the moment, but the workaround to your issue below should be to use the latest jruby-rack. How to override the one packaged in warbler is:

1. Additional Java .jar files to include. Note that if .jar files are placed
2. in lib (and not otherwise excluded) then they need not be mentioned here.
3. JRuby and JRuby-Rack are pre-loaded in this list. Be sure to include your
4. own versions if you directly set the value
5. config.java_libs += FileList["lib/java/*.jar"]
   config.java_libs.delete_if {|f| f =~ /jruby-rack/ || f =~ /jruby-complete/ }
   config.java_libs += FileList["lib/jruby-complete*.jar"]
   config.java_libs += FileList["lib/jruby-rack*.jar"]

then put the jruby-rack and jruby-complete jars you want to use in the lib/ dir.

The jruby-rack snapshot containing this fix is:
http://snapshots.repository.codehaus.org/org/jruby/rack/jruby-rack/0.9.5-SNAPSHOT/jruby-rack-0.9.5-20090625.190033-5.jar

You'll need to find the jruby jar you want to use and put it in the lib dir or remove that part from above.

My related blog entries:
http://stufftohelpyouout.blogspot.com/2009/07/fix-ioerrorio-errorbroken-pipestrange.html
http://stufftohelpyouout.blogspot.com/2009/06/how-to-get-warbler-to-include-custom.html

If you could post this into the Kenai ticket if it works for you, that would be great.
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A few more notes about the workaround:

• Do warble war:clean first to make sure it removes previous versions of jruby-rack, or it won't fix it (I did that. ugh!).
• Nick was the one who described how to do this for me and told me that the new jar fixed it (and he noted that in the ticket also).

Gary