From: Darrin Thompson <darrinth@...>
Date: 2009-08-29T01:55:04+09:00
Subject: Re: DRb Mysterious Stops

Michal Suchanek wrote:
> That many dup acks are somewhat suspicious but by themselves they
> should not cause a lockup. If there is network problem the connection
> should break eventually. However, some dumps of the part of the
> conversation that causes excessive packet duplication might be useful.
> Can you replicate the packet duplication with something simple like
> scp file transfer or the like?
> 

I can replicate it with a tiny tiny drb pair of programs.

On my SLES9 machine:
# cat test.rb
require 'drb'

class Echo
    def ping(length)
        return 'a' * length
    end
end

echo = Echo.new

DRb.start_service("druby://0.0.0.0:9000", echo)
DRb.thread.join

On my Windows machine:
require 'drb'

echo = DRb::DRbObject.new_with_uri("druby://172.31.192.159:9000")
response = echo.ping(ARGV[0].to_i)
puts response.length

When the program succeeds it's prints the number given. When it fails, 
it hangs until I kill it. I'm finding that short values always succeed, 
like 1024. I get some successful and some failed when I provide 44230 as 
the arg.

I have saved packet traces of a successful run at 1024 and a failed run 
at 1 Mb. The traces are a few K and 70+K respectively. I can provide 
them privately.

> Are some of the earlier machines also 64bit?
> 

Yes.

> I am not sure how 32bit vs 64bit integers work with marshalling. It
> should work but perhaps some testing to ensure it really works well
> would be a good idea.
> 

A lot of other 32/64 bit conversations with other machines are working 
fine, so I'm reluctant to go there.

--
Darrin
-- 
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