how to debug swift

I ran into a problem with swift and I was trying to debug it. When I did

python -m pdb /usr/bin/swift-proxy-server --verbose /etc/swift/proxy-server.conf

the debugging session would exit after this:
capture_stdio(logger)

I commented out this line, but ran into another problem, swift forks processes to handle request. If I break in a middle of a sub-process, pdb input/output is messed up (it doesn't echo and shows other strange behaviors).

I'd appreciate if someone can help me with instructions on debugging swift.