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From lars hofhansl <lhofha...@yahoo.com>
Subject Re: requiring zookeeper 3.4.x in 0.96
Date Wed, 18 Apr 2012 20:48:13 GMT
+1



----- Original Message -----
From: Jesse Yates <jesse.k.yates@gmail.com>
To: dev@hbase.apache.org
Cc: 
Sent: Wednesday, April 18, 2012 1:33 PM
Subject: requiring zookeeper 3.4.x in 0.96

Hi all,

I was working on some patches to make ZK a bit more sane using the
transaction operations recently added (in jira:
https://issues.apache.org/jira/browse/ZOOKEEPER-965
<http://zookeeper.apache.org/doc/r3.4.3/api/org/apache/zookeeper/ZooKeeper.html#transaction%28%29>
and in the api here:
http://zookeeper.apache.org/doc/r3.4.3/api/org/apache/zookeeper/ZooKeeper.html#transaction%28%29).
This takes care of a lot of race conditions, etc. that are inherently
present in zk.

Currently we (afaik) are not requiring ZooKeeper v.3.4.x in production and
instead allow users to run down to at least 3.3.x with the hbase's  3.4.x
client. Adding in transaction support will break this cross-version
functionality without a way of falling back as ZK doesn't (afaik) support
client-side look up of the server's version. Further, the fallback
functionality would be very dangerous if we assume transactions but fall
back to the non-transactional method; if we don't assume transactions, then
the transactional method is just wasted effort.

I'm proposing that in the singularity (0.96), when we move to requiring
Hadoop v1.0+ we also make it a requirement that people run ZooKeeper v3.4+

Thoughts?

Thanks!

-------------------
Jesse Yates
240-888-2200
@jesse_yates
jyates.github.com


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