Re: Migrate Cluster

[Alexander Shraer <sh...@gmail.com>]

assuming you're using 3.4 release and doing reboots to add/remove servers,
option 2 doesn't seem safe. For example,
if you have servers A, B, C and you're adding D and E, note that its
possible that C isn't fully up to date since A and B can make progress
without C's acks (2 out of 3). When you reboot all servers its possible
that C forms a quorum with D and E (3 out of 5) and is elected leader.
Then, anything more recent A and B had will be lost.

If I'm not mistaken option 1 shouldn't have this problem since any quorum
after each step always intersects any quorum before the step.

If you're using 3.5 release you should be able to do the whole migration in
a single reconfiguration step.

On Tue, Sep 29, 2015 at 11:31 AM, snair 123 <na...@outlook.com> wrote:

> Hello Experts
> I need to migrate an existing 3 node Zk ensemble to a different set of
> servers in a different networkSo servers A,B,C move to D,E,FWhat is the
> best way to do that without causing affecting the service
> This is is what we have been planning1. Add one node from the new network
> 2. Join and sync up 3. Remove one from the old network4. Do this for all
> the 3 nodes
> OR
> 1. Add 2 nodes in the new network2. Join and syncup3. Remove 2 nodes from
> the old network4. Add the 3rd node in the new network5. Make sure it is the
> leader ( a restart maybe ?)6. Remove the last remaining node from the old
> cluster
> The second option i would hope would ensure the leader stays in the
> network with most nodes and avoids problems due to network partitions ?
>
>

RE: Migrate Cluster

[snair 123 <na...@outlook.com>]

Got it . Thanks Alexander for the reply. Appreciate that.

> From: shralex@gmail.com
> Date: Wed, 30 Sep 2015 23:16:12 -0700
> Subject: Re: Migrate Cluster
> To: user@zookeeper.apache.org
> 
> assuming you're using 3.4 release and doing reboots to add/remove servers,
> option 2 doesn't seem safe. For example,
> if you have servers A, B, C and you're adding D and E, note that its
> possible that C isn't fully up to date since A and B can make progress
> without C's acks (2 out of 3). When you reboot all servers its possible
> that C forms a quorum with D and E (3 out of 5) and is elected leader.
> Then, anything more recent A and B had will be lost.
> 
> If I'm not mistaken option 1 shouldn't have this problem since any quorum
> after each step always intersects any quorum before the step.
> 
> If you're using 3.5 release you should be able to do the whole migration in
> a single reconfiguration step.
> 
> On Tue, Sep 29, 2015 at 11:31 AM, snair 123 <na...@outlook.com> wrote:
> 
> > Hello Experts
> > I need to migrate an existing 3 node Zk ensemble to a different set of
> > servers in a different networkSo servers A,B,C move to D,E,FWhat is the
> > best way to do that without causing affecting the service
> > This is is what we have been planning1. Add one node from the new network
> > 2. Join and sync up 3. Remove one from the old network4. Do this for all
> > the 3 nodes
> > OR
> > 1. Add 2 nodes in the new network2. Join and syncup3. Remove 2 nodes from
> > the old network4. Add the 3rd node in the new network5. Make sure it is the
> > leader ( a restart maybe ?)6. Remove the last remaining node from the old
> > cluster
> > The second option i would hope would ensure the leader stays in the
> > network with most nodes and avoids problems due to network partitions ?
> >
> >