HBASE-3655 Revision to HBase book, more examples in data model, more metrics, more performance -- part one
git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1083274 13f79535-47bb-0310-9956-ffa450edef68
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Michael Stack
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@ -319,7 +319,8 @@ Tables in HBase are initially created with one region by default. For bulk impo
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<title>Get/Scan</title>
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<para>Gets are implemented on top of Scans. The below discussion of
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Get applies equally to Scans.</para>
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<link xlink:href="http://hbase.apache.org/docs/current/api/org/apache/hadoop/hbase/client/Get.html">Get</link> applies equally to <link
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xlink:href="http://hbase.apache.org/docs/current/api/org/apache/hadoop/hbase/client/Scan.html">Scans</link>.</para>
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<para>By default, i.e. if you specify no explicit version, when
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doing a <literal>get</literal>, the cell whose version has the
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@ -343,6 +344,29 @@ Tables in HBase are initially created with one region by default. For bulk impo
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desired version and set the max versions to 1.</para>
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</listitem>
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</itemizedlist>
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</section>
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<section>
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<title>Default Get Example</title>
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<para>The following Get will only retrieve the current version of the row
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<programlisting>
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Get get = new Get( Bytes.toBytes("row1") );
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Result r = htable.get(get);
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byte[] b = r.getValue( Bytes.toBytes("cf"), Bytes.toBytes("attr") ); // returns current version of value
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</programlisting>
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</para>
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</section>
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<section>
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<title>Versioned Get Example</title>
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<para>The following Get will return the last 3 versions of the row.
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<programlisting>
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Get get = new Get( Bytes.toBytes("row1") );
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get.setMaxVersions(3); // will return last 3 versions of row
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Result r = htable.get(get);
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byte[] b = r.getValue( Bytes.toBytes("cf"), Bytes.toBytes("attr") ); // returns current version of value
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List<KeyValue> kv = r.getColumn( Bytes.toBytes("cf"), Bytes.toBytes("attr") ); // returns all versions of this column
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</programlisting>
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</para>
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</section>
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<section>
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@ -358,6 +382,27 @@ Tables in HBase are initially created with one region by default. For bulk impo
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<para>To overwrite an existing value, do a put at exactly the same
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row, column, and version as that of the cell you would
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overshadow.</para>
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<section>
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<title>Implicit Version Example</title>
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<para>The following Put will be implicitly versioned by HBase with the current time.
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<programlisting>
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Put put = new Put(Bytes.toBytes(row));
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put.add(Bytes.toBytes("cf"), Bytes.toBytes("attr1"), Bytes.toBytes( data));
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htable.put(put);
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</programlisting>
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</para>
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</section>
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<section>
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<title>Explicit Version Example</title>
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<para>The following Put has the version timestamp explicitly set.
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<programlisting>
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Put put = new Put( Bytes.toBytes( row ) );
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long explicitTimeInMs = 555; // just an example
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put.add(Bytes.toBytes("cf"), Bytes.toBytes("attr1"), explicitTimeInMs, Bytes.toBytes( data));
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htable.put(put);
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</programlisting>
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</para>
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</section>
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</section>
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<section>
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@ -259,15 +259,21 @@ of all regions.
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<section xml:id="client_dependencies"><title>Client configuration and dependencies connecting to an HBase cluster</title>
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<para>
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Since the HBase Master may move around, clients bootstrap by looking ZooKeeper. Thus clients
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require the ZooKeeper quorum information in a <filename>hbase-site.xml</filename> that
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is on their <varname>CLASSPATH</varname>.</para>
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Since the HBase Master may move around, clients bootstrap by looking to ZooKeeper for
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current critical locations. ZooKeeper is where all these values are kept. Thus clients
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require the location of the ZooKeeper ensemble information before they can do anything else.
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Usually this the ensemble location is kept out in the <filename>hbase-site.xml</filename> and
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is picked up by the client from the <varname>CLASSPATH</varname>.</para>
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<para>If you are configuring an IDE to run a HBase client, you should
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include the <filename>conf/</filename> directory on your classpath.
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include the <filename>conf/</filename> directory on your classpath so
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<filename>hbase-site.xml</filename> settings can be found (or
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add <filename>src/test/resources</filename> to pick up the hbase-site.xml
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used by tests).
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</para>
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<para>
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Minimally, a client of HBase needs the hbase, hadoop, log4j, commons-logging, and zookeeper jars
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in its <varname>CLASSPATH</varname> connecting to a cluster.
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Minimally, a client of HBase needs the hbase, hadoop, log4j, commons-logging, commons-lang,
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and zookeeper jars in its <varname>CLASSPATH</varname> connecting to a cluster.
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</para>
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<para>
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An example basic <filename>hbase-site.xml</filename> for client only
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@ -283,9 +289,31 @@ of all regions.
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</description>
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</property>
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</configuration>
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]]>
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</programlisting>
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]]></programlisting>
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</para>
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<section>
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<title>Java client configuration connecting to an HBase cluster</title>
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<subtitle>How Java reads <filename>hbase-site.xml</filename> content</subtitle>
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<para>The configuration used by a client is kept
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in an <link xlink:href="http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/HBaseConfiguration">HBaseConfiguration</link> instance.
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Through the factory method on HBaseConfiguration...
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<programlisting>Configuration config = HBaseConfiguration.create();</programlisting>
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.. a client will pick up a configuration sourced from the first <filename>hbase-site.xml</filename> found on
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the client's <varname>CLASSPATH</varname>, if one is present
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(We'll also factor in any <filename>hbase-default.xml</filename> found; an hbase-default.xml ships inside
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the <filename>hbase.X.X.X.jar</filename>).
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It is also possible to specify configuration directly without having to read from a
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<filename>hbase-site.xml</filename>. For examplt to set the
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<link linkend="zookeeper">zookeeper</link> ensemble for the cluster programmatically do as follows...
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<programlisting>Configuration config = HBaseConfiguration.create();
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config.set("hbase.zookeeper.quorum", "localhost"); // we are running zookeeper locally
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</programlisting>
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If multiple <link linkend="zookeeper">zookeeper</link> instances make up your zookeeper ensemble,
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they may be specified in a comma-list (just as in the <filename>hbase-site.xml</filename> file).
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This populated Configuration instance can then be passed to an
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<link xlink:href="http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/client/HTable.html">HTable</link> instance via the overloaded constructor.
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</para>
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</section>
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</section>
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</chapter>
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