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hbase-5036 book.xml architecture chapter minor mods regarding region-RS assignment 

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1214614 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Doug Meil 2011-12-15 03:56:03 +00:00
parent 6b60585fef
commit 37cbd5a38e
1 changed files with 16 additions and 25 deletions
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41
src/docbkx/book.xml
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@ -1319,6 +1319,8 @@ if (!b) {
<title>Startup Sequencing</title>
<para>The META location is set in ROOT first. Then META is updated with server and startcode values.
</para>
<para>For information on region-RegionServer assignment, see <xref linkend="regions.arch.assignment"/>.
</para>
</section>
</section> <!-- catalog -->
@ -1724,46 +1726,35 @@ scan.setFilter(filter);
<section xml:id="regions.arch.assignment.startup">
<title>Startup</title>
<para>When HBase starts regions are assigned as follows (short version):
</para>
<orderedlist>
<listitem>
<para>The Master invokes the <code>AssignmentManager</code> upon startup.</para>
<listitem>The Master invokes the <code>AssignmentManager</code> upon startup.
</listitem>
<listitem>
<para>The <code>AssignmentManager</code> looks at the existing region assignments
in META.</para>
<listitem>The <code>AssignmentManager</code> looks at the existing region assignments in META.
</listitem>
<listitem>
<para>If the region assignment is still valid (i.e., if the RegionServer) is still online
<listitem>If the region assignment is still valid (i.e., if the RegionServer) is still online
then the assignment is kept.
</para>
</listitem>
<listitem>
<para>If the assignment is invalid, then the <code>LoadBalancerFactory</code> is invoked to assign the
region. The <code>DefaultLoadBalancer</code> will randomly assign the region to a RegionServer.
</para>
<listitem>If the assignment is invalid, then the <code>LoadBalancerFactory</code> is invoked to assign the
region. The <code>DefaultLoadBalancer</code> will randomly assign the region to a RegionServer and
update META.
</listitem>
</orderedlist>
</orderedlist>
</para>
</section>
<section xml:id="regions.arch.assignment.failover">
<title>Failover</title>
<para>When a RegionServer fails (short version):
</para>
<orderedlist>
<listitem>
<para>The regions immediately become unavailable because the RegionServer is down.</para>
<listitem>The regions immediately become unavailable because the RegionServer is down.
</listitem>
<listitem>
<para>The Master will detect that the RegionServer has failed.</para>
<listitem>The Master will detect that the RegionServer has failed.
</listitem>
<listitem>
<para>The region assignments will be considered invalid and will be re-assigned just
<listitem>The region assignments will be considered invalid and will be re-assigned just
like the startup sequence.
</para>
</listitem>
</orderedlist>
</para>
</section>
@ -1784,9 +1775,9 @@ scan.setFilter(filter);
<orderedlist>
<listitem>First replica is written to local node
</listitem>
<listitem>Second replica to another node in same rack
<listitem>Second replica is written to another node in same rack
</listitem>
<listitem>Third replica to a node in another rack (if sufficient nodes)
<listitem>Third replica is written to a node in another rack (if sufficient nodes)
</listitem>
</orderedlist>
HBase eventually achieves locality for a region after a flush a compaction.