When starting Rails (3.2.18 on OS X) with

JAVA_OPTS="-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=5005" bundle exec rails c

That is, launching Rails through bundler with Java debugging agent, JVM dies to the following error:

Listening for transport dt_socket at address: 5005
ERROR: transport error 202: bind failed: Address already in use
ERROR: JDWP Transport dt_socket failed to initialize, TRANSPORT_INIT(510)
JDWP exit error AGENT_ERROR_TRANSPORT_INIT(197): No transports initialized [../../../src/share/back/debugInit.c:750]
FATAL ERROR in native method: JDWP No transports initialized, jvmtiError=AGENT_ERROR_TRANSPORT_INIT(197)

This seems to be because bundler ultimately loads Rails::ScriptRailsLoader which starts Rails by running exec RUBY, SCRIPT_RAILS, *ARGV if in_rails_application? which then spawns another JVM and probably the port has not been properly released when the second JVM tries to open it.

I can side-step the problem by JRUBY_OPTS="-J-Djruby.launch.inproc=true -J-Djruby.native.exec=false", but this is slightly unsatisfactory.