[Spread-users] Membership message vs regular message

Guo, Yanchao Yanchao.Guo at sac.com
Sun Feb 21 20:44:15 EST 2010

Hi Yair:

Now I understand the purpose of SELF_DISCARD message. The problem i want to address here is to eliminate communication between two publishers, as that is a waste of bandwidth, so the SELF_DISCARD message won't help me. 

However, introducing second group means another thread listening to the traffic... Is there a better way to do this? 


-----Original Message-----
From: spread-users-bounces at lists.spread.org on behalf of Guo, Yanchao
Sent: Fri 2/19/2010 5:34 AM
To: Yair Amir
Cc: spread-users at lists.spread.org
Subject: RE: [Spread-users] Membership message vs regular message
Thanks Yair. Some comments:

1: So you are saying that if the group_membership is set to 1, then the publisher don't have to join the group to receive the membership message? 
2: I depoly my server outside my LAN and client inside my LAN. To test the failure detection, I tried two things:
	a: pull out the network cable from the machine that my client is running on. In this case, both server and client is not able to receive any notification, but we I put in the cable, I received all the messages published in that interval;
	b: I reset the gateway of my LAN. In this case, client doesn't receive any notification. I can't check my server as I lost all ssh session. 

	In both cases, do you expect spread to detect the failure? In general, how to track the failure? I am tracking the Is_caused_network_mess messsage, is that the right way? 


-----Original Message-----
From: Yair Amir [mailto:yairamir at cs.jhu.edu] 
Sent: Friday, February 19, 2010 5:46 PM
To: Guo, Yanchao
Cc: spread-users at lists.spread.org
Subject: Re: [Spread-users] Membership message vs regular message


If you have only a single publisher you can use the self-discard flag and then publisher will not receive its own messages.

If you have more than one publisher, you can maintain a second group where publishers as well as receivers join (but no message is sent) to keep track of the membership of the main group.

Also - I think there is a slight inaccuracy in previous posts - Spread will detect failures even if you are not sending traffic if you run a daemon on the failed (or partitioned) machine and connect locally.
My understanding is that he only case where Spread does not immediately detect a failure is in certain setups where you have a client that connects to Spread remotely via TCP (with a remote daemon) and the client machine is partitioned.
This is a TCP/socket issue rather than a Spread issue.


	:) Yair.

On 2/19/10 2:29 AM, Guo, Yanchao wrote:
> Hi all, for my publisher application, I want it got notification when 
> some listeners joined the group. To do that, my publisher application 
> have to join the same group and receive messages. But the message the 
> publisher receives include both membership message and regular message.
> How can I configure my publisher application to only receive 
> membership messages?
> Thanks.
> Yanchao
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