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From Sergey Maslyakov <evol...@gmail.com>
Subject Re: Zookeeper ensemble backup questions?
Date Fri, 19 Jul 2013 18:38:34 GMT
Alexander,

I cannot speak to that intelligently. I don't know implementation and
design details well enough. However, a snapshot of this kind, if it is
produced by ZooKeeperServer.takeSnapshot() method, should contain not just
the DataTree content but the sessions too. I am not sure if this covers
ephemeral nodes though but I am pretty sure this is way Zookeeper server
takes snapshots driven by the transaction count.


Regards,
/Sergey


On Fri, Jul 19, 2013 at 1:26 PM, Alexander Shraer <shralex@gmail.com> wrote:

> Sergey,
>
> Can you explain what happens with ephemeral nodes during snapshot and
> restore ?
>
> Thanks,
> Alex
>
> On Fri, Jul 19, 2013 at 11:21 AM, Sergey Maslyakov <evolvah@gmail.com>
> wrote:
> > Jordan,
> >
> > It depends on the use case. Some use cases deal with 99% or more of
> static
> > non-ephemeral nodes. And this is why the Exhibitor approach does not work
> > for those use cases.
> >
> >
> > Regards,
> > /Sergey
> >
> >
> > On Fri, Jul 19, 2013 at 1:13 PM, Jordan Zimmerman <
> > jordan@jordanzimmerman.com> wrote:
> >
> >> I'm a bit late to this one but I don't understand the need for complete
> >> backup of ZK data. In my experience, 99% of ZNodes are ephemeral.
> >> Therefore, it would be wrong to restore those nodes. In a disaster, the
> >> connection sessions would expire and you would not want ephemeral nodes
> >> restored. This is why in Exhibitor I took the approach of selective
> restore.
> >>
> >> -Jordan
> >>
> >> On Jul 19, 2013, at 11:00 AM, jack ma <jackma1402@gmail.com> wrote:
> >>
> >> > I asked those question in the thread
> >> >
> >>
> http://mail-archives.apache.org/mod_mbox/zookeeper-user/201307.mbox/%3cCAB+cfdwhOV0JfB04=MpO_+i-4ou=VbL=EG2XS557+j+698jx3A@mail.gmail.com%3e
> >> ,
> >> > but there is no response for that.
> >> >
> >> > So I posted those questions again here, hopefully I could get helps
> >> > from the community.
> >> >
> >> > I want to make sure I am fully understanding the procedures of
> zookeeper
> >> > backup and disaster recovery:
> >> >
> >> > For the backup procedures at zookeeper assemble:
> >> > (1) Login to any host which state is "Serving"
> >> >           Question:
> >> >                  Do I have to login to leader node, or any node is ok?
> >> > (2) Copy latest snapshot file and transaction log from version-2
> >> directory.
> >> >           Question:
> >> >                  How to make sure we do not copy corrupt files if the
> >> > snapshot/transaction log is in the middle of update? Do we have to
> >> shutdown
> >> > the node to make the copy?
> >> >                  besides the transaction log and snapshot, do we have
> to
> >> > copy other files such as the ecoch files
> >> >
> >> > For the disaster recovery procedures at zookeeper assemble:
> >> > (1) recreate the machines for the zookeeper ensemble
> >> > (2) copy snapshot/transaction log we backed up into the zookeeper
> >> > dataDir\version-2 and logDir\version2.
> >> >           Question:
> >> >                 Do we have to copy the epoch files?
> >> >                 Do we have to copy snapshot/transaction log backed up
> to
> >> > all the zookeeper node, or just the first node we starts?
> >> >
> >> > Appreciate your time and help.
> >> > Jack
> >>
> >>
>

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