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From Apache Wiki <wikidi...@apache.org>
Subject [Hadoop Wiki] Trivial Update of "ZooKeeper/HBaseUseCases" by stack
Date Fri, 20 Nov 2009 18:29:14 GMT
Dear Wiki user,

You have subscribed to a wiki page or wiki category on "Hadoop Wiki" for change notification.

The "ZooKeeper/HBaseUseCases" page has been changed by stack.
http://wiki.apache.org/hadoop/ZooKeeper/HBaseUseCases?action=diff&rev1=14&rev2=15

--------------------------------------------------

  === root-region-server ===
  This znode holds the location of the server hosting the root of all tables in hbase.
  
- Idea is to hoist the whole region up into zk rather than have it out as a fully-fledged
hbase region; it has little info in it.
- 
  === master ===
  
- This is current master.  If more than one master, they fight over who it should be.  They
all try to grab this znode.
+ This is current master.  If more than one master, they fight over who it should be.  They
all try to grab this znode.  When this node evaporates, masters try to grab it again.  Whoever
wins picks up the master role.
  
  === rs ===
  
  A directory in which there is a znode per hbase server (regionserver) participating in the
cluster.  They register themselves when they come on line.  They name of the znode is a random
number, the regions' startcode, so can tell if regionserver has been restarted (We should
fix this so server names are more descriptive).
+ 
+ If regionserver session in zk is lost, this znode evaporates.  The regionserver will get
the disconnect message and shut itself down.  Master will start the clean up process gathering
its write-ahead logs, splitting them and divvying the edits out per region so they are available
when regions are opened in new locations on other running regionservers.
  
  === shutdown ===
  If cluster is to shutdown.

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