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HBASE-3715 Book.xml - adding architecture section on client, adding section on spec-ex under mapreduce 

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1087588 13f79535-47bb-0310-9956-ffa450edef68
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Michael Stack 2011-04-01 05:45:10 +00:00
parent 9e6308c918
commit 22e5b51c7b
2 changed files with 36 additions and 0 deletions
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CHANGES.txt
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@ -117,6 +117,8 @@ Release 0.91.0 - Unreleased
HBASE-3720 Book.xml - porting conceptual-view / physical-view sections of
HBaseArchitecture wiki (Doug Meil via Stack)
HBASE-3705 Allow passing timestamp into importtsv (Andy Sautins via Stack)
HBASE-3715 Book.xml - adding architecture section on client, adding section
on spec-ex under mapreduce (Doug Meil via Stack)
TASK
HBASE-3559 Move report of split to master OFF the heartbeat channel

34
src/docbkx/book.xml
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@ -124,6 +124,16 @@ throws InterruptedException, IOException {
}</programlisting>
</para>
</section>
<section xml:id="mapreduce.specex">
<title>Speculative Execution</title>
<para>It is generally advisable to turn off speculative execution for
MapReduce jobs that use HBase as a source. This can either be done on a
per-Job basis through properties, on on the entire cluster. Especially
for longer running jobs, speculative execution will create duplicate
map-tasks which will double-write your data to HBase; this is probably
not what you want.
</para>
</section>
</chapter>
<chapter xml:id="schema">
@ -694,6 +704,30 @@ public static byte[][] getHexSplits(String startKey, String endKey, int numRegio
<chapter xml:id="architecture">
<title>Architecture</title>
<section xml:id="client">
<title>Client</title>
<para>The HBase client
<link xlink:href="http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/client/HTable.html">HTable</link>
is responsible for finding RegionServers that are serving the
particular row range of interest. It does this by querying
the <code>.META.</code> and <code>-ROOT</code> catalog tables
(TODO: Explain). After locating the required
region(s), the client <emphasis>directly</emphasis> contacts
the RegionServer serving that region (i.e., it does not go
through the master) and issues the read or write request.
This information is cached in the client so that subsequent requests
need not go through the lookup process. Should a region be reassigned
either by the master load balancer or because a RegionServer has died,
the client will requery the catalog tables to determine the new
location of the user region.
</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>
<para>For connection configuration information, see the <link linkend="client_dependencies">configuration</link> section.
</para>
</section>
<section xml:id="daemons">
<title>Daemons</title>
<section xml:id="master"><title>Master</title>