[jgroups-dev] Dynamic Host Problem.

Hello Bela.

I'm kuwon and I found some problem.

We are using JGroups in production mode.
And our team are preparing disaster recovery system for Customer system.

But the guy who is in charge of the disaster recovery system that he copied
the customer system's jgroups configuration and
started in the disaster recovery system.

After that he recognized that initial_host was not correct. Because he used
customer system's iniitial_host instead of disaster recovery system's ip.

Customer's is
<TCPPING timeout="3000"^M

initial_hosts="${jgroups.tcpping.initial_hosts:100.254.163.31[7800],
100.254.16
3.32[7800]}"^M
             port_range="2"^M
             num_initial_members="4"/>^M

After he changed the disaster's recovery system's initial_hosts from
customer's to  disaster's system.

*Problem occurred,* the problem is disaster's cluster joins the customer's
cluster even disaster's inital_hosts is it's own ip, not a customers's ip.

We were very difficult to  find this problem, and I reviewed whole jgroups
sources and found some code.

MERGE2 check the members periodically using TCPPING's dynamic_hosts.

*/** https://jira.jboss.org/jira/browse/JGRP-989 */*
protected final BoundedList<PhysicalAddress> dynamic_hosts=new
BoundedList<PhysicalAddress>(max_dynamic_hosts);

*When we have A,B and C listed in initial_hosts but later D and E join, and
we have a partition {A,B,C} and {D,E}, when the partition heals later, we
have no way of merging the 2 subgroups back into 1 because initial_hosts
doesn't contain D or E.
SOLUTION: dynamically add members not in initial_hosts to initial_hosts on
view changes. Keep the number of dynamically added members bounded.*

*This caused this problem, I think if the coord check the dynamic_hosts to
merge other node, it also check the other node's initial_host*
*whether it contains the coord's host address.*
*Becuase D,E does not contains the ABC's IP address in initial_host anymore.
*
*
*
*And we could not restart ABC's node to remove the dnamic_hosts because this
ABC are running in production mode.*
*
*
*Thanks and i hope this help you to enhance my favorite jgroups.*

-- 
Blessings.
Kuwon Kang
............................................................
IT specialist and architect.
Java technology engineer.
JavaEE architect/developer.
Spring Framework specialist.
Solution developer.
Grid computing.

- Model Driven Architecture.
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............................................................
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 http://www.prever.co.kr/
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M 010 9440 9090
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God's love is eternal and leads us to live for heaven and His glory

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