From: "S. Robert James" <srobertjames@...>
Date: 2007-01-24T06:20:07+09:00
Subject: Re: Does Ruby's FTP lib have a ghostly bug?

I just added FTP conneciton caching, which seems to have removed the
problem.  Therefore, I'll assume that this was *not* a ftp.rb problem,
but rather connections being refused when too many came in.  (This
didn't show up on simple command line testing, because the rate was
much slower.)  I'll add that being that the EOFError message is quite
cryptic, perhaps whoever maintains ftp.rb could make a more
comprehnsible error message (along with the actual OS level socket
error).

I also need to thank Ara.   By asking me what I thought was an obvious
question (does command line ftp work), he forced me to communicate my
assumption ("command line works, cryptic error message --> ergo ftp.rb
problem") and consequently rethink it.  Is the command line doing the
same thing as the app?  No, it's making a lot fewer connections.

This has served to me as a good lesson in debugging:
1. Can you prove the problem is where you think it is?  Expand the
scope.
2. With any bug, there's something that you're wrong about.  Perhaps
those things which give you the information you are sure of are
themselves wrong.  That is, don't just look for problems where you see
them -- look for problems in all of your proofs to get there.
3. Last, always tell the problem to someone else.  Having to
communicate to someone forces you to rethink it.  And if that someone
else wants proof (like most good Rubyists), it forces you to prove it.
In this case, when I glanced at the src code, I thought it _did_ cache
the connections. But I was going to paste that line in to the list and
saw that, in this scenario, it wasn't caching them.

Thanks Ara! And thanks comp.lang.ruby!