From: Ken Hilton <kenosis@...>
Date: 2004-04-28T04:34:04+09:00
Subject: $stdin, thread blocking and DRb (for lack of a better subject :)

Greetings friends in Ruby-land,



I've crafted a Ruby application and its giving me a little trouble and I'm
hoping someone out there can give me some insight into the problem.



The app is composed of 3 threads (other than the primary thread, which waits
for the others to finish once its created them):  the first thread is bound
to a code block which reads email via NET::POP3; the 2nd thread is that of a
simple DRb server; and the third thread is bound to a code block that
implements a simple command shell which reads lines from $stdin.



The application works wonderfully but w/the following problem: threads 1 and
2 block when the command shell thread reads from $stdin.  Adjusting thread
priorities had no affect on the problem.  When the command shell thread is
stopped all works as expected (email is read in the background and in
parallel w/the DRb server accepting requests from an test harness running as
a separate ruby session.)  I've checked all the Ruby books and docs I have
and can't find an explanation as to why this should be happening.  My
suspicion is that because $stdin belongs to the ruby application main thread
and is being used by the command shell thread, that for some reason the
blocking read of $stdin is holding off the other threads.  This speculation
is supported by the fact that entering a command to the shell allows all 3
threads to run in parallel until the command is completed and the next read
of $stdin occurs.



Any insight ya'll can lend will be much appreciated.



Ken.