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[11/15] hbase git commit: HBASE-14066 clean out old docbook docs from
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http://git-wip-us.apache.org/repos/asf/hbase/blob/0acbff24/src/main/docbkx/cp.xml
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-<?xml version="1.0" encoding="UTF-8"?>
-<chapter
- version="5.0"
- xml:id="cp"
- xmlns="http://docbook.org/ns/docbook"
- xmlns:xlink="http://www.w3.org/1999/xlink"
- xmlns:xi="http://www.w3.org/2001/XInclude"
- xmlns:svg="http://www.w3.org/2000/svg"
- xmlns:m="http://www.w3.org/1998/Math/MathML"
- xmlns:html="http://www.w3.org/1999/xhtml"
- xmlns:db="http://docbook.org/ns/docbook">
- <!--
-/**
- * Licensed to the Apache Software Foundation (ASF) under one
- * or more contributor license agreements. See the NOTICE file
- * distributed with this work for additional information
- * regarding copyright ownership. The ASF licenses this file
- * to you under the Apache License, Version 2.0 (the
- * "License"); you may not use this file except in compliance
- * with the License. You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
--->
- <title>Apache HBase Coprocessors</title>
- <para> HBase coprocessors are modeled after the coprocessors which are part of Google's BigTable
- (<link xlink:href="http://www.scribd.com/doc/21631448/Dean-Keynote-Ladis2009"/>, pages
- 66-67.). Coprocessors function in a similar way to Linux kernel modules. They provide a way to
- run server-level code against locally-stored data. The functionality they provide is very
- powerful, but also carries great risk and can have adverse effects on the system, at the level
- of the operating system. The information in this chapter is primarily sourced and heavily reused
- from Mingjie Lai's blog post at <link
- xlink:href="https://blogs.apache.org/hbase/entry/coprocessor_introduction"/>. </para>
-
- <para> Coprocessors are not designed to be used by end users of HBase, but by HBase developers who
- need to add specialized functionality to HBase. One example of the use of coprocessors is
- pluggable compaction and scan policies, which are provided as coprocessors in <link
- xlink:href="HBASE-6427">HBASE-6427</link>. </para>
-
- <section>
- <title>Coprocessor Framework</title>
- <para>The implementation of HBase coprocessors diverges from the BigTable implementation. The
- HBase framework provides a library and runtime environment for executing user code within the
- HBase region server and master processes. </para>
- <para> The framework API is provided in the <link
- xlink:href="https://hbase.apache.org/apidocs/org/apache/hadoop/hbase/coprocessor/package-summary.html">coprocessor</link>
- package.</para>
- <para>Two different types of coprocessors are provided by the framework, based on their
- scope.</para>
- <variablelist>
- <title>Types of Coprocessors</title>
- <varlistentry>
- <term>System Coprocessors</term>
- <listitem>
- <para>System coprocessors are loaded globally on all tables and regions hosted by a region
- server.</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term>Table Coprocessors</term>
- <listitem>
- <para>You can specify which coprocessors should be loaded on all regions for a table on a
- per-table basis.</para>
- </listitem>
- </varlistentry>
- </variablelist>
-
- <para>The framework provides two different aspects of extensions as well:
- <firstterm>observers</firstterm> and <firstterm>endpoints</firstterm>.</para>
- <variablelist>
- <varlistentry>
- <term>Observers</term>
- <listitem>
- <para>Observers are analogous to triggers in conventional databases. They allow you to
- insert user code by overriding upcall methods provided by the coprocessor framework.
- Callback functions are executed from core HBase code when events occur. Callbacks are
- handled by the framework, and the coprocessor itself only needs to insert the extended
- or alternate functionality.</para>
- <variablelist>
- <title>Provided Observer Interfaces</title>
- <varlistentry>
- <term><link
- xlink:href="https://hbase.apache.org/apidocs/org/apache/hadoop/hbase/coprocessor/RegionObserver.html">RegionObserver</link></term>
- <listitem>
- <para>A RegionObserver provides hooks for data manipulation events, such as Get,
- Put, Delete, Scan. An instance of a RegionObserver coprocessor exists for each
- table region. The scope of the observations a RegionObserver can make is
- constrained to that region. </para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><link
- xlink:href="https://hbase.apache.org/apidocs/org/apache/hadoop/hbase/coprocessor/RegionServerObserver.html">RegionServerObserver</link></term>
- <listitem>
- <para>A RegionServerObserver provides for operations related to the RegionServer,
- such as stopping the RegionServer and performing operations before or after
- merges, commits, or rollbacks.</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><link
- xlink:href="http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/coprocessor/WALObserver.html">WALObserver</link></term>
- <listitem>
- <para>A WALObserver provides hooks for operations related to the write-ahead log
- (WAL). You can observe or intercept WAL writing and reconstruction events. A
- WALObserver runs in the context of WAL processing. A single WALObserver exists on
- a single region server.</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><link
- xlink:href="https://hbase.apache.org/apidocs/org/apache/hadoop/hbase/coprocessor/MasterObserver.html">MasterObserver</link></term>
- <listitem>
- <para>A MasterObserver provides hooks for DDL-type operation, such as create,
- delete, modify table. The MasterObserver runs within the context of the HBase
- master. </para>
- </listitem>
- </varlistentry>
- </variablelist>
- <para>More than one observer of a given type can be loaded at once. Multiple observers are
- chained to execute sequentially by order of assigned priority. Nothing prevents a
- coprocessor implementor from communicating internally among its installed
- observers.</para>
- <para>An observer of a higher priority can preempt lower-priority observers by throwing an
- IOException or a subclass of IOException.</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term>Endpoints (HBase 0.96.x and later)</term>
- <listitem>
- <para>The implementation for endpoints changed significantly in HBase 0.96.x due to the
- introduction of protocol buffers (protobufs) (<link
- xlink:href="https://issues.apache.org/jira/browse/HBASE-5448">HBASE-5488</link>). If
- you created endpoints before 0.96.x, you will need to rewrite them. Endpoints are now
- defined and callable as protobuf services, rather than endpoint invocations passed
- through as Writable blobs</para>
- <para>Dynamic RPC endpoints resemble stored procedures. An endpoint can be invoked at any
- time from the client. When it is invoked, it is executed remotely at the target region
- or regions, and results of the executions are returned to the client.</para>
- <para>The endpoint implementation is installed on the server and is invoked using HBase
- RPC. The client library provides convenience methods for invoking these dynamic
- interfaces. </para>
- <para>An endpoint, like an observer, can communicate with any installed observers. This
- allows you to plug new features into HBase without modifying or recompiling HBase
- itself.</para>
- <itemizedlist>
- <title>Steps to Implement an Endpoint</title>
- <listitem><para>Define the coprocessor service and related messages in a <filename>.proto</filename> file</para></listitem>
- <listitem><para>Run the <command>protoc</command> command to generate the code.</para></listitem>
- <listitem><para>Write code to implement the following:</para>
- <itemizedlist>
- <listitem><para>the generated protobuf Service interface</para></listitem>
- <listitem>
- <para>the new <link
- xlink:href="https://hbase.apache.org/apidocs/org/apache/hadoop/hbase/client/HTable.html#coprocessorService(byte[])">org.apache.hadoop.hbase.coprocessor.CoprocessorService</link>
- interface (required for the <link
- xlink:href="https://hbase.apache.org/apidocs/org/apache/hadoop/hbase/regionserver/RegionCoprocessorHost.html">RegionCoprocessorHost</link>
- to register the exposed service)</para></listitem>
- </itemizedlist>
- </listitem>
- <listitem><para>The client calls the new HTable.coprocessorService() methods to perform the endpoint RPCs.</para></listitem>
- </itemizedlist>
-
- <para>For more information and examples, refer to the API documentation for the <link
- xlink:href="https://hbase.apache.org/apidocs/org/apache/hadoop/hbase/client/coprocessor/package-summary.html">coprocessor</link>
- package, as well as the included RowCount example in the
- <filename>/hbase-examples/src/test/java/org/apache/hadoop/hbase/coprocessor/example/</filename>
- of the HBase source.</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term>Endpoints (HBase 0.94.x and earlier)</term>
- <listitem>
- <para>Dynamic RPC endpoints resemble stored procedures. An endpoint can be invoked at any
- time from the client. When it is invoked, it is executed remotely at the target region
- or regions, and results of the executions are returned to the client.</para>
- <para>The endpoint implementation is installed on the server and is invoked using HBase
- RPC. The client library provides convenience methods for invoking these dynamic
- interfaces. </para>
- <para>An endpoint, like an observer, can communicate with any installed observers. This
- allows you to plug new features into HBase without modifying or recompiling HBase
- itself.</para>
- <itemizedlist>
- <title>Steps to Implement an Endpoint</title>
- <listitem>
- <bridgehead>Server-Side</bridgehead>
- <itemizedlist>
- <listitem>
- <para>Create new protocol interface which extends CoprocessorProtocol.</para>
- </listitem>
- <listitem>
- <para>Implement the Endpoint interface. The implementation will be loaded into and
- executed from the region context.</para>
- </listitem>
- <listitem>
- <para>Extend the abstract class BaseEndpointCoprocessor. This convenience class
- hides some internal details that the implementer does not need to be concerned
- about, ˆ such as coprocessor framework class loading.</para>
- </listitem>
- </itemizedlist>
- </listitem>
- <listitem>
- <bridgehead>Client-Side</bridgehead>
- <para>Endpoint can be invoked by two new HBase client APIs:</para>
- <itemizedlist>
- <listitem>
- <para><code>HTableInterface.coprocessorProxy(Class<T> protocol, byte[]
- row)</code> for executing against a single region</para>
- </listitem>
- <listitem>
- <para><code>HTableInterface.coprocessorExec(Class<T> protocol, byte[]
- startKey, byte[] endKey, Batch.Call<T,R> callable)</code> for executing
- over a range of regions</para>
- </listitem>
- </itemizedlist>
- </listitem>
- </itemizedlist>
- </listitem>
- </varlistentry>
- </variablelist>
- </section>
-
- <section>
- <title>Examples</title>
- <para>An example of an observer is included in
- <filename>hbase-examples/src/test/java/org/apache/hadoop/hbase/coprocessor/example/TestZooKeeperScanPolicyObserver.java</filename>.
- Several endpoint examples are included in the same directory.</para>
- </section>
-
-
-
- <section>
- <title>Building A Coprocessor</title>
-
- <para>Before you can build a processor, it must be developed, compiled, and packaged in a JAR
- file. The next step is to configure the coprocessor framework to use your coprocessor. You can
- load the coprocessor from your HBase configuration, so that the coprocessor starts with HBase,
- or you can configure the coprocessor from the HBase shell, as a table attribute, so that it is
- loaded dynamically when the table is opened or reopened.</para>
- <section>
- <title>Load from Configuration</title>
- <para> To configure a coprocessor to be loaded when HBase starts, modify the RegionServer's
- <filename>hbase-site.xml</filename> and configure one of the following properties, based
- on the type of observer you are configuring: </para>
- <itemizedlist>
- <listitem>
- <para><code>hbase.coprocessor.region.classes</code>for RegionObservers and
- Endpoints</para>
- </listitem>
- <listitem>
- <para><code>hbase.coprocessor.wal.classes</code>for WALObservers</para>
- </listitem>
- <listitem>
- <para><code>hbase.coprocessor.master.classes</code>for MasterObservers</para>
- </listitem>
- </itemizedlist>
- <example>
- <title>Example RegionObserver Configuration</title>
- <para>In this example, one RegionObserver is configured for all the HBase tables.</para>
- <screen language="xml"><![CDATA[
-<property>
- <name>hbase.coprocessor.region.classes</name>
- <value>org.apache.hadoop.hbase.coprocessor.AggregateImplementation</value>
- </property> ]]>
- </screen>
- </example>
-
- <para> If multiple classes are specified for loading, the class names must be comma-separated.
- The framework attempts to load all the configured classes using the default class loader.
- Therefore, the jar file must reside on the server-side HBase classpath.</para>
-
- <para>Coprocessors which are loaded in this way will be active on all regions of
- all tables. These are the system coprocessor introduced earlier. The first listed
- coprocessors will be assigned the priority <literal>Coprocessor.Priority.SYSTEM</literal>.
- Each subsequent coprocessor in the list will have its priority value incremented by one
- (which reduces its priority, because priorities have the natural sort order of Integers). </para>
- <para>When calling out to registered observers, the framework executes their callbacks methods
- in the sorted order of their priority. Ties are broken arbitrarily.</para>
- </section>
-
- <section>
- <title>Load from the HBase Shell</title>
- <para> You can load a coprocessor on a specific table via a table attribute. The following
- example will load the <systemitem>FooRegionObserver</systemitem> observer when table
- <systemitem>t1</systemitem> is read or re-read. </para>
- <example>
- <title>Load a Coprocessor On a Table Using HBase Shell</title>
- <screen>
-hbase(main):005:0> <userinput>alter 't1', METHOD => 'table_att',
- 'coprocessor'=>'hdfs:///foo.jar|com.foo.FooRegionObserver|1001|arg1=1,arg2=2'</userinput>
-<computeroutput>Updating all regions with the new schema...
-1/1 regions updated.
-Done.
-0 row(s) in 1.0730 seconds</computeroutput>
-
-hbase(main):006:0> <userinput>describe 't1'</userinput>
-<computeroutput>DESCRIPTION ENABLED
- {NAME => 't1', coprocessor$1 => 'hdfs:///foo.jar|com.foo.FooRegio false
- nObserver|1001|arg1=1,arg2=2', FAMILIES => [{NAME => 'c1', DATA_B
- LOCK_ENCODING => 'NONE', BLOOMFILTER => 'NONE', REPLICATION_SCOPE
- => '0', VERSIONS => '3', COMPRESSION => 'NONE', MIN_VERSIONS =>
- '0', TTL => '2147483647', KEEP_DELETED_CELLS => 'false', BLOCKSIZ
- E => '65536', IN_MEMORY => 'false', ENCODE_ON_DISK => 'true', BLO
- CKCACHE => 'true'}, {NAME => 'f1', DATA_BLOCK_ENCODING => 'NONE',
- BLOOMFILTER => 'NONE', REPLICATION_SCOPE => '0', VERSIONS => '3'
- , COMPRESSION => 'NONE', MIN_VERSIONS => '0', TTL => '2147483647'
- , KEEP_DELETED_CELLS => 'false', BLOCKSIZE => '65536', IN_MEMORY
- => 'false', ENCODE_ON_DISK => 'true', BLOCKCACHE => 'true'}]}
-1 row(s) in 0.0190 seconds</computeroutput>
- </screen>
- </example>
-
- <para>The coprocessor framework will try to read the class information from the coprocessor
- table attribute value. The value contains four pieces of information which are separated by
- the <literal>|</literal> character.</para>
-
- <itemizedlist>
- <listitem>
- <para>File path: The jar file containing the coprocessor implementation must be in a
- location where all region servers can read it. You could copy the file onto the local
- disk on each region server, but it is recommended to store it in HDFS.</para>
- </listitem>
- <listitem>
- <para>Class name: The full class name of the coprocessor.</para>
- </listitem>
- <listitem>
- <para>Priority: An integer. The framework will determine the execution sequence of all
- configured observers registered at the same hook using priorities. This field can be
- left blank. In that case the framework will assign a default priority value.</para>
- </listitem>
- <listitem>
- <para>Arguments: This field is passed to the coprocessor implementation.</para>
- </listitem>
- </itemizedlist>
- <example>
- <title>Unload a Coprocessor From a Table Using HBase Shell</title>
- <screen>
-hbase(main):007:0> <userinput>alter 't1', METHOD => 'table_att_unset',</userinput>
-hbase(main):008:0* <userinput>NAME => 'coprocessor$1'</userinput>
-<computeroutput>Updating all regions with the new schema...
-1/1 regions updated.
-Done.
-0 row(s) in 1.1130 seconds</computeroutput>
-
-hbase(main):009:0> <userinput>describe 't1'</userinput>
-<computeroutput>DESCRIPTION ENABLED
- {NAME => 't1', FAMILIES => [{NAME => 'c1', DATA_BLOCK_ENCODING => false
- 'NONE', BLOOMFILTER => 'NONE', REPLICATION_SCOPE => '0', VERSION
- S => '3', COMPRESSION => 'NONE', MIN_VERSIONS => '0', TTL => '214
- 7483647', KEEP_DELETED_CELLS => 'false', BLOCKSIZE => '65536', IN
- _MEMORY => 'false', ENCODE_ON_DISK => 'true', BLOCKCACHE => 'true
- '}, {NAME => 'f1', DATA_BLOCK_ENCODING => 'NONE', BLOOMFILTER =>
- 'NONE', REPLICATION_SCOPE => '0', VERSIONS => '3', COMPRESSION =>
- 'NONE', MIN_VERSIONS => '0', TTL => '2147483647', KEEP_DELETED_C
- ELLS => 'false', BLOCKSIZE => '65536', IN_MEMORY => 'false', ENCO
- DE_ON_DISK => 'true', BLOCKCACHE => 'true'}]}
-1 row(s) in 0.0180 seconds </computeroutput>
- </screen>
- </example>
- <warning>
- <para>There is no guarantee that the framework will load a given coprocessor successfully.
- For example, the shell command neither guarantees a jar file exists at a particular
- location nor verifies whether the given class is actually contained in the jar file.
- </para>
- </warning>
- </section>
- </section>
- <section>
- <title>Check the Status of a Coprocessor</title>
- <para>To check the status of a coprocessor after it has been configured, use the
- <command>status</command> HBase Shell command.</para>
- <screen>
-hbase(main):020:0> <userinput>status 'detailed'</userinput>
-<computeroutput>version 0.92-tm-6
-0 regionsInTransition
-master coprocessors: []
-1 live servers
- localhost:52761 1328082515520
- requestsPerSecond=3, numberOfOnlineRegions=3, usedHeapMB=32, maxHeapMB=995
- -ROOT-,,0
- numberOfStores=1, numberOfStorefiles=1, storefileUncompressedSizeMB=0, storefileSizeMB=0, memstoreSizeMB=0,
-storefileIndexSizeMB=0, readRequestsCount=54, writeRequestsCount=1, rootIndexSizeKB=0, totalStaticIndexSizeKB=0,
-totalStaticBloomSizeKB=0, totalCompactingKVs=0, currentCompactedKVs=0, compactionProgressPct=NaN, coprocessors=[]
- .META.,,1
- numberOfStores=1, numberOfStorefiles=0, storefileUncompressedSizeMB=0, storefileSizeMB=0, memstoreSizeMB=0,
-storefileIndexSizeMB=0, readRequestsCount=97, writeRequestsCount=4, rootIndexSizeKB=0, totalStaticIndexSizeKB=0,
-totalStaticBloomSizeKB=0, totalCompactingKVs=0, currentCompactedKVs=0, compactionProgressPct=NaN, coprocessors=[]
- t1,,1328082575190.c0491168a27620ffe653ec6c04c9b4d1.
- numberOfStores=2, numberOfStorefiles=1, storefileUncompressedSizeMB=0, storefileSizeMB=0, memstoreSizeMB=0,
-storefileIndexSizeMB=0, readRequestsCount=0, writeRequestsCount=0, rootIndexSizeKB=0, totalStaticIndexSizeKB=0,
-totalStaticBloomSizeKB=0, totalCompactingKVs=0, currentCompactedKVs=0, compactionProgressPct=NaN,
-coprocessors=[AggregateImplementation]
-0 dead servers </computeroutput>
- </screen>
- </section>
- <section>
- <title>Monitor Time Spent in Coprocessors</title>
- <para>HBase 0.98.5 introduced the ability to monitor some statistics relating to the amount of
- time spent executing a given coprocessor. You can see these statistics via the HBase Metrics
- framework (see <xref linkend="hbase_metrics"/> or the Web UI for a given Region Server, via
- the <guilabel>Coprocessor Metrics</guilabel> tab. These statistics are valuable for debugging
- and benchmarking the performance impact of a given coprocessor on your cluster. Tracked
- statistics include min, max, average, and 90th, 95th, and 99th percentile. All times are shown
- in milliseconds. The statistics are calculated over coprocessor
- execution samples recorded during the reporting interval, which is 10 seconds by default. The
- metrics sampling rate as described in <xref linkend="hbase_metrics" />.</para>
- <figure>
- <title>Coprocessor Metrics UI</title>
- <mediaobject>
- <imageobject>
- <imagedata fileref="coprocessor_stats.png" width="100%"/>
- </imageobject>
- <caption>
- <para>The Coprocessor Metrics UI shows statistics about time spent executing a given
- coprocessor, including min, max, average, and 90th, 95th, and 99th percentile.</para>
- </caption>
- </mediaobject>
- </figure>
- </section>
- <section>
- <title>Status of Coprocessors in HBase</title>
- <para> Coprocessors and the coprocessor framework are evolving rapidly and work is ongoing on
- several different JIRAs. </para>
- </section>
-</chapter>
http://git-wip-us.apache.org/repos/asf/hbase/blob/0acbff24/src/main/docbkx/customization.xsl
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-<?xml version="1.0"?>
-<xsl:stylesheet
- xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
- version="1.0">
-<!--
-/**
- * Licensed to the Apache Software Foundation (ASF) under one
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- * distributed with this work for additional information
- * regarding copyright ownership. The ASF licenses this file
- * to you under the Apache License, Version 2.0 (the
- * "License"); you may not use this file except in compliance
- * with the License. You may obtain a copy of the License at
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--->
- <xsl:import href="urn:docbkx:stylesheet"/>
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- <xsl:output method="html" encoding="UTF-8" indent="no"/>
-
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