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From Apache Wiki <wikidi...@apache.org>
Subject [Hadoop Wiki] Trivial Update of "Hbase/MasterRewrite" by stack
Date Mon, 19 Oct 2009 23:56:04 GMT
Dear Wiki user,

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The "Hbase/MasterRewrite" page has been changed by stack.
http://wiki.apache.org/hadoop/Hbase/MasterRewrite?action=diff&rev1=4&rev2=5

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

  Initial Master Rewrite design came of conversations had at the hbase hackathon held at StumbleUpon,
August 5-7, 2009 ([[https://issues.apache.org/jira/secure/attachment/12418561/HBase+Hackathon+Notes+-+Sunday.pdf|Jon
Gray kept notes]]).  The umbrella issue for the master rewrite is [[https://issues.apache.org/jira/browse/HBASE-1816|HBASE-1816]].
 Timeline is hbase 0.20.1.
  
  == What does the Master do now? ==
+ Here's a bit of a refresher on what Master currently does:
-  * Splitting
-   * Should be distributed
   * Region Assignment
-   * Balancing
+   * On startup and balancing as regions are created and deleted as regions grow and split.
   * Scan root/meta
    * Make sure Regions are online
    * Delete parents if no reference
   * Manage schema alter/online/offline
   * Admin
+   * Distributes out administered close, flush, compact messages
-   * Close region
-   * Flush
-   * Compact/Major compact
   * Watches ZK for its own lease and for regionservers so knows when to run recovery
+ 
+ == Problems with current Master ==
+  * Balancer is not testable unless you spin up full cluster
+  * State transitions are not atomic; various messaging sequences can produce confused cluster
state.
  
  == Design ==
  

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