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 <[email protected]> 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 <[email protected]> > 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 < > > [email protected]> 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 <[email protected]> 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+698j...@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 > >> > >> >
