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From "Chris T." <c.turks...@gmail.com>
Subject Re: About ZooKeeper Dynamic Reconfiguration
Date Fri, 27 Sep 2019 06:30:21 GMT
Let me write this from memory. :)

We have the following:

-A running zookeeper cluster with adminserver enabled
-One or more balancer client processes (one per datacenter), of which one
has a master role through some leader election. The master does the work,
the others do nothing.
-In our case, we work with a designated survivor datacenter (has 3
participants and the other non survivor datacenter has 2 participant and 1
observer ) , and the balancer always resides in the designated survivor
datacenter. This is not a requirement, due to above leader election.
-A balancer client configuration file with all predefined Zookeeper servers
(use it for building the client connection string and generating the server
list). Each predefined server under normal condition has a running
Zookeeper in either participant or observer role.

Balancer design:

buildDatacenterAndServerModel(configurationFile) {
  enum zookeeperRole PARTICIPANT, OBSERVER, NONE, DOWN
  object datacenter has servers
  object server has zookeeperRole configuredRole, zookeeperRole activeRole
  parse(configurationFile) into (datacenter, servers);
}

shiftMajority(designatedSurvivorDatacenter) {

designatedSurvivorDatacenter.someObserver.dynamicReconfigure(server=PARTICIPANT)
  otherDatacenter.someParticipant.dynamicReconfigure(server=OBSERVER)
}


balanceServerRoles() {
  if (designatedSurvivorDatacenter.hasMinimumQuorum)
someParticipant.dynamicReconfigure(server=OBSERVER)
  if (quorumSize.aboveSafeLimit)
someObserver.dynamicReconfigure(server=PARTICIPANT)
  //This is a lot more complicated than 2 simple commands, you need an
algorithm or define several scenarios.
}


main() {
 buildDatacenterAndServerModel(configurationFile);
  while (iAmLeader) {
    parse(zk.getData(/zookeeper/config)) into servers.configuredRole
    foreach(server) getServerRole(server:8081/commands/stat) into
servers.activeRole

    foreach (server.activeRole=DOWN) dynamicReconfigure(server=OBSERVER) ;
server.setConfiguredRole(OBSERVER)

    if(designatedSurvivorDatacenter != datacenter.hasMajority)
shiftMajority(designatedSurvivorDatacenter)

    balanceServerRoles()
  }
}



Hope this helps. If you need more details, I can check the actual code
coming week.

On Fri, Sep 27, 2019 at 5:06 AM Gao,Wei <Wei.Gao@arcserve.com> wrote:

> Hi oo4load,
>   Could you please tell me how to implements this to avoid the problem
> above?
> Thanks
>
>
>
> --
> Sent from: http://zookeeper-user.578899.n2.nabble.com/
>

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