From: Mark Probert <probertm@...>
Date: 2004-01-20T11:10:00+09:00
Subject: threads, mutex, regexp and trouble

Hello, rubyists.

I have a bit of a problem suing threads.  The program reads in a list of 
commands, then fires them off, via a telnet session, to another device, 
collecting data as it goes.  

On a one-by-one basis, everything is fine.  the commands works, 
everything is peachy.  The problem is I have to do 250+ sessions in a 
fairly limited time.  Ok, use threads.

The problem is that I appear to be occassional tromping a variable, and 
mutexing doesn't seem to work.  Sometimes its ok, often it not.

The code in question looks like:

      @threads << Thread.new(node) { |idx|
	nn, ip, usr, pwd = idx.split(/:/)

	begin
	  bsn = BSN.new(ip, @timeout)

	  # login and run each command
	  if bsn.login then

	    @cmds.each do |cmd|
	      mutex.synchronize do
		  puts "~~>> cmd=#{cmd}"
		  bsn.cmd(cmd)
	      end
	    end
	    bsn.logout
	  else
	    puts " !! Unable to reach node= #{nn}"
	  end
      }
    @threads.each { |thr| thr.join }

The problem is that the "cmd" variable seems to get mashed by a regexp 
match within bsn.cmd().  A good run looks like:

  .. Running 2 commands on 2 nodes.
  .. threading now ...
~~>> cmd=show subs isp=*_eeua
~~>> cmd=show subs isp=*_eeua

A bad run looks like:

  .. Running 2 commands on 2 nodes.
  .. threading now ...
~~>> cmd=show subs isp=*_eeua
~~>> cmd=show subs isp=ebg1_eeua

These commands come from a text file and the line is "show subs 
isp=*_eeua".

The regexp does a match on data returned from the node.  The first match 
for the first node is "ebg1_eeua".  So, it seems that the regexp is 
confusing the thread.

Any thoughts?

Thanks,

-mark.