[Spread-users] Spread 4.0 daemon "goes to sleep" on XP network disconnect

Steve Duff Steve.Duff at vivista.sungard.com
Wed Aug 8 06:43:05 EDT 2007

I'm evaluating Spread 4.0 as a possible candidate for a group
communication task, and I've noticed an unexpected behaviour (well,
unexpected to me, anyway). 

I have three machines A, B, and C each running a daemon, and with two
local clients (i.e. on the same machine), A1, A2, B1 etc. all subscribed
to the same group.

If I pull the network cable out of machine A, daemons B and C notice
this and tell B1, B2, C1 and C2 of the membership change. A1 and A2 get
no membership change.

As expected, messages can be exchanged between clients on B and C, but
when messages are sent through A1 they are not delivered anywhere (even
to A2). If I then reconnect A, then clients on A, B, and C all get
membership change messages, and any messages sent from A1 while
disconnected are now delivered to all clients.

My expectation was that daemon A would eventually tell A1 and A2 that
they had been separated from the rest of the group, but this doesn't
happen. This makes the membership change message that they DO receive on
being reconnected seem spurious. Also the messages that are delivered on
reconnect are out of context and would cause problems when they are

I tried this initially on three virtual machines, but have confirmed the
behaviour is the same with real machines. I've tried using a single
spread segment, and three separate spread segments, but this also makes
no difference. I've also tried using two switches and separating A from
B and C by disconnecting the switches from each other - in that case A
works entirely as expected.

I think the possibilities are:

A) My expectation that A should separate and notify it's clients in this
circumstance is simply wrong, in which case could somebody please
explain why.
B) This is a "feature" caused by Windows XP networking, i.e. it doesn't
happen on other platforms.
C) It is a feature of the Spread implementation, and I need to work
around it at the application level.

I would appreciate if anyone can offer any help with this? 



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