When using eventmachine as a TCP server, it can be useful to know when the network buffers have filled up and we are starting to queue inside of the EventableSocketChannel (so you can take action and close the socket as necessary, to avoid overflowing the heap and crashing your process). The C ruby version has a way of accessing this internal queue, so I've added it to the jruby version.
Making outbound data queue size available to user
Not being able to access this queue size created big problems for us. We wound up forking EM just to add it, which sucks.
FYI, in case you're worried about this being a pain in the ass to merge in to 1.0.0.beta.4, it's not. Cherry pick does the trick without conflicts.
Superseded by #556 and available in eventmachine 1.0.6 and newer.