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From Apache Wiki <wikidi...@apache.org>
Subject [Hadoop Wiki] Trivial Update of "ZooKeeper/FAQ" by ChangSong
Date Wed, 10 Nov 2010 21:22:08 GMT
Dear Wiki user,

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The "ZooKeeper/FAQ" page has been changed by ChangSong.
The comment on this change is: added a comment about a minor problem using DNS RR.
http://wiki.apache.org/hadoop/ZooKeeper/FAQ?action=diff&rev1=14&rev2=15

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   * DNS round robin: this setup involves one hostname and a list of IPs. ZK clients correctly
make used of a list of IPs returned by DNS query. Thus this setup works the same way as multiple
hostname (IP) argument to zookeeper_init. The drawback is that when an ensemble cluster configuration
changes like server addition/removal, it may take a while to propagate the DNS entry change
in all DNS servers and DNS client caching (nscd for example) TTL issue.
  
  In conclusion, DNS RR works as good as a list of ensemble IP arguments except cluster reconfiguration
case.
+ It turns out that there is a minor problem with DNS RR. If you are using a tool such as
zktop.py, it does not take care of a list of host IP returned by a DNS server. 
  

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