[Hadoop Wiki] Update of "Hbase/ZookeeperIntegration" by Misty

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The "Hbase/ZookeeperIntegration" page has been changed by Misty:
https://wiki.apache.org/hadoop/Hbase/ZookeeperIntegration?action=diff&rev1=5&rev2=6

- = HBase/Zookeeper Integration Documentation =
+ The HBase Wiki is in the process of being decommissioned. The info that used to be on this page has moved to http://hbase.apache.org/book.html#zookeeper. Please update your bookmarks.
  
- == Introduction ==
- 
- [[http://hadoop.apache.org/zookeeper/|Apache ZooKeeper]] is for HBase what Chubby is for Bigtable. The goal of using ZK is that a coordination manager is useful to decentralize the master's job and it improves availability. In Bigtable's paper, Chubby is used to :
- 
-  * Ensure there is at most 1 active master at any time
-  * Store the bootstrap location
-  * Discover tablet servers and finalize tablet server death
-  * Store the schema information
-  * Store access control lists
- 
- It has been discussed that, for the moment, only the three first bullets will be implemented. Also, in order to have a lesser impact on current users, ZK will be optional and a basic implementation will be provided in HBase. For those that will use ZK, the overhead will be like using HDFS.
- 
- For updates, see [[https://issues.apache.org/jira/browse/HBASE-546|HBASE-546]]
- 
- == The Interface ==
- 
- The interface must support macro operations so that dirty implementation details are hidden. 
- 
- The current interface would be : 
- 
- {{{
- ...
- 
- public interface DistributedLockInterface extends VersionedProtocol {
- 
-   public static final long versionID = 1L;
- 
-   /**
-    * Used to bootstrap. Used to find a tablet location when a client doesn't have
-    * META information
-    * 
-    * @return root region information
-    */
-   public byte[] getRootRegion() throws IOException;
- 
-   /**
-    * Used by regionserver at startup or by master if a regionserver is down
-    * 
-    * @param filename File name of the lock
-    */
-   public void acquireLock(String filename) throws IOException;
- 
-   /**
-    * Used by regionserver at shutdown or by master if a regionserver is down
-    * 
-    * @param filename File name of the lock
-    */
-   public void releaseLock(String filename) throws IOException;
- 
-   /**
-    * Used by master at startup
-    */
-   public void acquireMasterLock() throws IOException;
- 
-   /**
-    * Used by master at startup to discover live servers
-    * @return All the addresses of the region servers
-    */
-   public HServerAddress[] getLiveRegionServers() throws IOException;
- 
- }
- 
- }}}
- 
- 
- 
- == The HBase Implementation ==
- 
- This implementation of the interface would be master-based, this means that it doesn't support master failover and won't provide better availability. 
- 
- See [[https://issues.apache.org/jira/browse/HBASE-708|HBASE-708]]
- 
- == The ZK Integration ==
- 
- Not so soon...
-