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From Apache Wiki <wikidi...@apache.org>
Subject [Hadoop Wiki] Update of "Hbase/HbaseArchitecture" by izaakrubin
Date Fri, 22 Aug 2008 21:17:46 GMT
Dear Wiki user,

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The following page has been changed by izaakrubin:
http://wiki.apache.org/hadoop/Hbase/HbaseArchitecture

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  = Current Status =
  
  As of this writing (2008/08/22), there are approximately 79,500 lines of code in 
- "src/contrib/hbase/src/java/org/apache/hadoop/hbase/" directory on the Hadoop SVN trunk.
+ "hbase/trunk/src/java/org/apache/hadoop/hbase/" directory on the Hadoop SVN trunk.
  
  Also included in this directory are approximately 14,000 lines of test cases.
  
  Issues and TODOs:
   1. Modify RPC and amend how hbase uses RPC.  In particular, some messages will use the
current RPC mechanism and others will use raw sockets.  Raw sockets will be used for sending
the data of some serialized objects; the idea is that we can hard-code the creation/interpretation
of the serialized data and avoid introspection.
-  1. Vuk Ercegovac [[MailTo(vercego AT SPAMFREE us DOT ibm DOT com)]] of IBM Almaden Research
pointed out that keeping HBase HRegion edit logs in HDFS is currently flawed.  HBase writes
edits to logs and to a memcache.  The 'atomic' write to the log is meant to serve as insurance
against abnormal !RegionServer exit: on startup, the log is rerun to reconstruct an HRegion's
last wholesome state. But files in HDFS do not 'exist' until they are cleanly closed -- something
that will not happen if !RegionServer exits without running its 'close'.
+  1. Vuk Ercegovac [[MailTo(vercego AT SPAMFREE us DOT ibm DOT com)]] of IBM Almaden Research
pointed out that keeping HBase HRegion edit logs in HDFS is currently flawed.  HBase writes
edits to logs and to a memcache.  The 'atomic' write to the log is meant to serve as insurance
against abnormal !RegionServer exit: on startup, the log is rerun to reconstruct an HRegion's
last wholesome state. But files in HDFS do not 'exist' until they are cleanly closed -- something
that will not happen if !RegionServer exits without running its 'close'.  This issue will
be addressed in HBase-0.19.0.
   1. The HMemcache lookup structure is relatively inefficient
  
  Release News:
-  * HBase 0.2.0 was released in early August and runs on Hadoop 0.17.1.
+  * HBase-0.2.0 was released in early August and runs on Hadoop-0.17.1.
-  * Work is underway on releasing HBase 0.2.1 for Hadoop 0.17.2.1, and HBase 0.3 for Hadoop
0.18.  Looking farther ahead, HBase 0.4 will run on Hadoop 0.19.
+  * Work is underway on releasing HBase-0.2.1 for Hadoop-0.17.2.1, and HBase-0.18.0 for Hadoop-0.18.
 Looking farther ahead, HBase-0.19.0 will run with Hadoop-0.19.  Note that the HBase release
numbering schema has changed to align with the version of Hadoop with which it runs: 0.3.x
will be called 0.18.x, and 0.4.x will be called 0.19.x.
  
  See [https://issues.apache.org/jira/browse/HBASE?report=com.atlassian.jira.plugin.system.project:roadmap-panel&subset=3
hbase issues] for list of whats being currently worked on.
  

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