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HBase >> mail # dev >> HBase Replication use cases


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HBase Replication use cases
Hello All,

I have been doing testing on the HBase replication (0.90.4, and 0.92 variants).

Here are some of the findings:

a) 0.90+ is not that great in handling out znode changes; in an
ongoing replication, if I delete a peer and a region server goes to
the znode to update the log status, the region server aborts itself
when it sees a missing znode.

Recoverable Zookeeper seems to have fix this in 0.92+?

0.92 has lot of new features (start/stop handle, master master, cyclic).

But there are corner cases with the start/stop switches.
i)  A log is en-queue when the replication state is set to true. When we
start the cluster, it is true and the starting region server takes the
new log into the queue. If I do a stop_replication, and there is a log
roll, and then I do a start_replication, the current log will not be
replicated, as it has missed the opportunity of being added to the queue.

ii) If I _start_ a region server when the replication state is set to
false, its log will not be added to the queue. Now, if I do a
start_replication, its log will not be replicated.

iii) Removing a peer doesn't result in master region server abort, but
in case of zk is down and there is a log roll, it will abort. Not a
serious one as zk is down so the cluster is not healthy anyway.

I was looking for jiras (including 2611), and stumbled upon 2223. I
don't think there is any thing like time based partition behavior (as
mentioned in the jira description). Though. the patch has lot of other
nice things which indeed are in existing code. Please correct me if I
miss  anything.

Having said that, I wonder about other folks out there use it.
Their experience, common issues (minor + major) they come across.
I did find a ppt by Jean Daniel at oscon mentioning about using it in
SU production.

I plan to file jiras for the above ones and will start digging in.

Look forward for your responses.

Thanks,
Himanshu