Re: [jgroups-dev] Need information about Jgroup communication in jgroups 2.6.5

Hi Bela,

Thanks for your kind support.

However I have some more question.
I was searching for this and found http://olex.openlogic.com/packages/jgroups/2.6.7.GA#package_detail_tabs
Which shows it contains fix around this in 2.6.13 GA.

Note: I have tried using 2.8 version with our application. However I see some API incompatible issues.

Please suggest.

Thanks
Ashish Giri


-----Original Message-----
From: Bela Ban [mailto:[email protected]] 
Sent: Tuesday, February 15, 2011 8:23 PM
To: Ashish Giri
Cc: [email protected]
Subject: Re: [jgroups-dev] Need information about Jgroup communication in jgroups 2.6.5

2.8 and higher

On 2/15/11 1:59 PM, Ashish Giri wrote:
> Hi Bela,
>
> I was going through your blog http://belaban.blogspot.com/2009/04/those-damn-edge-cases.html.
>
> It seems that we are also facing similar kind of issue. We are using 2.6.5 version.
>
> Could you please confirm which version of jgroups include fix for above UNICAST related bug?
>
> Thanks,
> Ashish Giri
>
> -----Original Message-----
> From: Bela Ban [mailto:[email protected]]
> Sent: Monday, February 14, 2011 12:28 PM
> To: [email protected]
> Subject: Re: [jgroups-dev] Need information about Jgroup communication in jgroups 2.6.5
>
>
>
> On 2/13/11 3:07 PM, Ashish Giri wrote:
>> Hi Team,
>>
>>
>>
>> We are stuck to a scenario when we have three servers[A, B and C].All three
>> servers are interconnected.
>>
>>
>>
>> What will happen if route to B from A is disconnected. However B is still
>> reachable from C and C is reachable from A.
>>
>>
>>
>> How view will be represented in this case in each server?
>
> It depends on the failure detection protocols and on who is coordinator.
> Assuming A is coordinator and VERIFY_SUSPECT is in the stack, the
> following will happen:
> - In FD, A pings B, B pings C and C pings A
> - A won't get any heartbeat acks from B
> - A suspects B and broadcasts a SUSPECT event
> - A's VERIFY_SUSPECT will try to reach B again, but doesn't get any response
> - A excludes B and installs the new view {A,C} in  A and C
> - B still has view {A,B,C}
> - When B tries to ping C, C shuns B
> - B then leave the cluster and tries to reconnect. Because it cannot
> talk to A, this will go on forever
>
>
> You can actually simulate the above case easily by adding<DISCARD
> use_gui="true"/>  just above UDP. This will pop up a dialog box, in which
> you can interactively drop communication  to/from any member, even
> asymmetric links are possible (A can talk to B. but B cannot talk to A).
>
> The above behavior was changed in 2.8: shunning [2] doesn't exist
> anymore, it was replaced by merging, and merging was also improved to
> handle asymmetric cases [1].
>
>
> [1] http://belaban.blogspot.com/2009/04/those-damn-edge-cases.html
> [2] http://belaban.blogspot.com/2009/06/shunning-has-been-shunned.html
>
>

-- 
Bela Ban
Lead JGroups / Clustering Team
JBoss

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