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From dm...@apache.org
Subject svn commit: r1243550 - /hbase/trunk/src/docbkx/book.xml
Date Mon, 13 Feb 2012 15:00:51 GMT
Author: dmeil
Date: Mon Feb 13 15:00:51 2012
New Revision: 1243550

URL: http://svn.apache.org/viewvc?rev=1243550&view=rev
Log:
hbase-5390.  book.xml - adding section in Arch/Master about what happens if master dies.

Modified:
    hbase/trunk/src/docbkx/book.xml

Modified: hbase/trunk/src/docbkx/book.xml
URL: http://svn.apache.org/viewvc/hbase/trunk/src/docbkx/book.xml?rev=1243550&r1=1243549&r2=1243550&view=diff
==============================================================================
--- hbase/trunk/src/docbkx/book.xml (original)
+++ hbase/trunk/src/docbkx/book.xml Mon Feb 13 15:00:51 2012
@@ -1378,6 +1378,9 @@ if (!b) {
          the client will requery the catalog tables to determine the new
          location of the user region. 
     </para>
+    <para>See <xref linkend="master.runtime"/> for more information about the
impact of the Master on HBase Client
+    communication.
+    </para>
     <para>Administrative functions are handled through <link xlink:href="http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/client/HBaseAdmin.html">HBaseAdmin</link>
     </para>
 	   <section xml:id="client.connections"><title>Connections</title>
@@ -1661,6 +1664,15 @@ rs.close();
          take over the Master role.
          </para>
        </section>
+       <section xml:id="master.runtime"><title>Runtime Impact</title>
+         <para>A common dist-list question is what happens to an HBase cluster when
the Master goes down.  Because the
+         HBase client talks directly to the RegionServers, the cluster can still function
in a "steady 
+         state."  Additionally, per <xref linkend="arch.catalog"/> ROOT and META exist
as HBase tables (i.e., are
+         not resident in the Master).  However, the Master controls critical functions such
as RegionServer failover and 
+         completing region splits.  So while the cluster can still run <emphasis>for
a time</emphasis> without the Master, 
+         the Master should be restarted as soon as possible.     
+         </para>
+       </section>
        <section xml:id="master.api"><title>Interface</title>
          <para>The methods exposed by <code>HMasterInterface</code> are
primarily metadata-oriented methods:
          <itemizedlist>



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