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@@ -179,6 +179,27 @@ document.write("Last Published: " + document.lastModified);
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<a href="#ch_administration">Administration</a>
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<ul class="minitoc">
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<li>
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+<a href="#sc_designing">Designing a ZooKeeper Deployment</a>
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+</li>
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+<li>
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+<a href="#sc_provisioning">Provisioning</a>
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+</li>
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+<li>
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+<a href="#sc_strengthsAndLimitations">Things to Consider: ZooKeeper Strengths and Limitations</a>
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+</li>
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+<li>
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+<a href="#sc_administering">Administering</a>
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+</li>
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+<li>
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+<a href="#sc_monitoring">Monitoring</a>
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+</li>
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+<li>
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+<a href="#sc_logging">Logging</a>
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+</li>
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+<li>
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+<a href="#sc_troubleshooting">Troubleshooting</a>
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+</li>
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+<li>
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<a href="#sc_configuration">Configuration Parameters</a>
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<ul class="minitoc">
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<li>
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@@ -196,10 +217,7 @@ document.write("Last Published: " + document.lastModified);
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</ul>
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</li>
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<li>
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-<a href="#sc_zkCommands">Zookeeper Commands: The Four Letter Words</a>
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-</li>
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-<li>
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-<a href="#sc_monitoring">Monitoring</a>
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+<a href="#sc_zkCommands">ZooKeeper Commands: The Four Letter Words</a>
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</li>
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<li>
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<a href="#sc_dataFileManagement">Data File Management</a>
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@@ -267,17 +285,17 @@ document.write("Last Published: " + document.lastModified);
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</ul>
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<p>The first two sections assume you are interested in installing
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- Zookeeper in a production environment such as a datacenter. The final
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- section covers situations in which you are setting up Zookeeper on a
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+ ZooKeeper in a production environment such as a datacenter. The final
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+ section covers situations in which you are setting up ZooKeeper on a
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limited basis - for evaluation, testing, or development - but not in a
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production environment.</p>
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<a name="N10032"></a><a name="sc_systemReq"></a>
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<h3 class="h4">System Requirements</h3>
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-<p>Zookeeper runs in Java, release 1.5 or greater, as group of hosts
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- called a quorum. Three Zookeeper hosts per quorum is the minimum
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- recommended quorum size. At Yahoo!, Zookeeper is usually deployed on
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- dedicated RHEL boxes, with dual-core processors, 2GB of RAM, and 80GB
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- IDE harddrives.</p>
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+<p>ZooKeeper runs in Java, release 1.5 or greater (JDK 5 or greater).
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+ It runs as group of hosts called a quorum. Three ZooKeeper hosts per
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+ quorum is the minimum recommended quorum size. At Yahoo!, ZooKeeper is
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+ usually deployed on dedicated RHEL boxes, with dual-core processors, 2GB
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+ of RAM, and 80GB IDE harddrives.</p>
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<a name="N1003C"></a><a name="sc_zkMulitServerSetup"></a>
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<h3 class="h4">Clustered (Multi-Server) Setup</h3>
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<p>For reliable ZooKeeper service, you should deploy ZooKeeper in a
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@@ -295,11 +313,12 @@ document.write("Last Published: " + document.lastModified);
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<li>
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-<p>Install the Java JDK:</p>
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+<p>Install the Java JDK. You can use the native packaging system
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+ for your system, or download the JDK from:</p>
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<p>
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-<span class="codefrag computeroutput">$yinst -i jdk-1.6.0.00_3 -br test </span>
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+<a href="http://java.sun.com/javase/downloads/index.jsp">http://java.sun.com/javase/downloads/index.jsp</a>
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</p>
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</li>
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@@ -307,22 +326,29 @@ document.write("Last Published: " + document.lastModified);
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<li>
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-<p>Set the Java heap size. This is very important, to avoid
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- swapping, which will seriously degrade Zookeeper performance. To
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- determine the correct value, load tests, make sure you are well
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- below the usage limit that would cause you to swap. Be conservative
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- - use a maximum heap size of 3GB for a 4GB machine.</p>
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+<p>Set the Java heap size. This is very important to avoid
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+ swapping, which will seriously degrade ZooKeeper performance. To
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+ determine the correct value, use load tests, and make sure you are
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+ well below the usage limit that would cause you to swap. Be
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+ conservative - use a maximum heap size of 3GB for a 4GB
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+ machine.</p>
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</li>
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<li>
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-<p>Install the Zookeeper Server Package:</p>
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+<p>Install the ZooKeeper Server Package. It can be downloaded
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+ from:
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+ </p>
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<p>
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-<span class="codefrag computeroutput">$ yinst install -nostart zookeeper_server </span>
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+
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+<a href="http://hadoop.apache.org/zookeeper/releases.html">
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+ http://hadoop.apache.org/zookeeper/releases.html
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+ </a>
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+
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</p>
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</li>
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@@ -370,7 +396,7 @@ server.3=zoo3:2888</span>
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<li>
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<p>If your configuration file is set up, you can start
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- Zookeeper:</p>
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+ ZooKeeper:</p>
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<p>
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@@ -406,7 +432,7 @@ server.3=zoo3:2888</span>
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<p>In C, you can compile either the single threaded client or
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the multithreaded client: or n the c subdirectory in the
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- Zookeeper sources. This compiles the single threaded
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+ ZooKeeper sources. This compiles the single threaded
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client:</p>
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@@ -428,8 +454,8 @@ server.3=zoo3:2888</span>
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<p>Running either program gives you a shell in which to execute
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- simple file-system-like operations. To connect to Zookeeper with the multithreaded
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- client, for example, you would run:</p>
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+ simple file-system-like operations. To connect to ZooKeeper with the
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+ multithreaded client, for example, you would run:</p>
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<p>
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@@ -439,32 +465,94 @@ server.3=zoo3:2888</span>
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</li>
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</ol>
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-<a name="N100CE"></a><a name="sc_singleAndDevSetup"></a>
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+<a name="N100D0"></a><a name="sc_singleAndDevSetup"></a>
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<h3 class="h4">Single Server and Developer Setup</h3>
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-<p>If you want to setup Zookeeper for development purposes, you will
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- probably want to setup a single server instance of Zookeeper, and then
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+<p>If you want to setup ZooKeeper for development purposes, you will
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+ probably want to setup a single server instance of ZooKeeper, and then
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install either the Java or C client-side libraries and bindings on your
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development machine.</p>
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<p>The steps to setting up a single server instance are the similar
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to the above, except the configuration file is simpler. You can find the
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- complete instructions in the <a href="zookeeperStarted.html#sc_InstallingSingleMode">Installing
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- and Running Zookeeper in SIngle Server Mode</a> section of the
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- <a href="zookeeperStarted.html">Zookeeper
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- Getting Started Guide</a>.</p>
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+ complete instructions in the <a href="zookeeperStarted.html#sc_InstallingSingleMode">Installing and
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+ Running ZooKeeper in SIngle Server Mode</a> section of the <a href="zookeeperStarted.html">ZooKeeper Getting Started
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+ Guide</a>.</p>
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<p>For information on installing the client side libraries, refer to
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the <a href="zookeeperProgrammers.html#Bindings">Bindings</a>
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- section of the <a href="zookeeperProgrammers.html">Zookeeper
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+ section of the <a href="zookeeperProgrammers.html">ZooKeeper
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Programmer's Guide</a>.</p>
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</div>
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-<a name="N100EF"></a><a name="ch_administration"></a>
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+<a name="N100F1"></a><a name="ch_administration"></a>
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<h2 class="h3">Administration</h2>
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<div class="section">
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<p>This section contains information about running and maintaining
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ZooKeeper and covers these topics: </p>
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<ul>
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+<li>
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+
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+<p>
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+<a href="#sc_designing">Designing a ZooKeeper Deployment</a>
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+</p>
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+
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+</li>
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+
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+
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+<li>
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+
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+<p>
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+<a href="#sc_provisioning">Provisioning</a>
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+</p>
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+
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+</li>
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+
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+
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+<li>
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+
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+<p>
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+<a href="#sc_strengthsAndLimitations">Things to Consider: ZooKeeper Strengths and Limitations</a>
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+</p>
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+
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+</li>
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+
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+
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+<li>
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+
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+<p>
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+<a href="#sc_administering">Administering</a>
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+</p>
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+
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+</li>
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+
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+
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+<li>
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+
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+<p>
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+<a href="#sc_monitoring">Monitoring</a>
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+</p>
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+
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+</li>
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+
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+
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+<li>
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+
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+<p>
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+<a href="#sc_logging">Logging</a>
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+</p>
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+
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+</li>
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+
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+
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+<li>
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+
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+<p>
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+<a href="#sc_troubleshooting">Troubleshooting</a>
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+</p>
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+
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+</li>
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+
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+
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<li>
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<p>
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@@ -477,7 +565,7 @@ server.3=zoo3:2888</span>
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<li>
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<p>
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-<a href="#sc_zkCommands">Zookeeper Commands: The Four Letter Words</a>
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+<a href="#sc_zkCommands">ZooKeeper Commands: The Four Letter Words</a>
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</p>
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</li>
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@@ -510,370 +598,371 @@ server.3=zoo3:2888</span>
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</li>
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</ul>
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-<a name="N10123"></a><a name="sc_configuration"></a>
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+<a name="N1015D"></a><a name="sc_designing"></a>
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+<h3 class="h4">Designing a ZooKeeper Deployment</h3>
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+<p></p>
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+<a name="N10166"></a><a name="sc_provisioning"></a>
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+<h3 class="h4">Provisioning</h3>
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+<p></p>
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+<a name="N1016F"></a><a name="sc_strengthsAndLimitations"></a>
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+<h3 class="h4">Things to Consider: ZooKeeper Strengths and Limitations</h3>
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+<p></p>
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+<a name="N10178"></a><a name="sc_administering"></a>
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+<h3 class="h4">Administering</h3>
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+<p></p>
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+<a name="N10181"></a><a name="sc_monitoring"></a>
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+<h3 class="h4">Monitoring</h3>
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+<p></p>
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+<a name="N1018A"></a><a name="sc_logging"></a>
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+<h3 class="h4">Logging</h3>
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+<p></p>
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+<a name="N10193"></a><a name="sc_troubleshooting"></a>
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+<h3 class="h4">Troubleshooting</h3>
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+<p></p>
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+<a name="N1019C"></a><a name="sc_configuration"></a>
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<h3 class="h4">Configuration Parameters</h3>
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<p>ZooKeeper's behavior is governed by the ZooKeeper configuration
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- file. This file is designed so that the exact same file can be used by
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- all the servers that make up a ZooKeeper server assuming the disk
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- layouts are the same. If servers use different configuration files,
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- care must be taken to ensure that the list of servers in all of the
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- different configuration files match.</p>
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-<a name="N1012C"></a><a name="sc_minimumConfiguration"></a>
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+ file. This file is designed so that the exact same file can be used by
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+ all the servers that make up a ZooKeeper server assuming the disk
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+ layouts are the same. If servers use different configuration files, care
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+ must be taken to ensure that the list of servers in all of the different
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+ configuration files match.</p>
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+<a name="N101A5"></a><a name="sc_minimumConfiguration"></a>
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<h4>Minimum Configuration</h4>
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-<p>Here are the minimum configuration keywords that must be
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- defined in the configuration file:</p>
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+<p>Here are the minimum configuration keywords that must be defined
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+ in the configuration file:</p>
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<dl>
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-
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-
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+
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<dt>
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<term>clientPort</term>
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</dt>
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<dd>
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<p>the port to listen for client connections; that is, the
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- port that clients attempt to connect to.</p>
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+ port that clients attempt to connect to.</p>
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</dd>
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-
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+
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<dt>
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<term>dataDir</term>
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</dt>
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<dd>
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-<p>the location where Zookeeper will store the in-memory
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- database snapshots and, unless specified otherwise, the
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- transaction log of updates to the database.</p>
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+<p>the location where ZooKeeper will store the in-memory
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+ database snapshots and, unless specified otherwise, the
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+ transaction log of updates to the database.</p>
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<div class="note">
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<div class="label">Note</div>
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<div class="content">
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-
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-<p>Be careful where you put the transaction log. A
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- dedicated transaction log device is key to consistent good
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- performance. Putting the log on a busy device will adversely
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- effect performance.</p>
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+<p>Be careful where you put the transaction log. A
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+ dedicated transaction log device is key to consistent good
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+ performance. Putting the log on a busy device will adversely
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+ effect performance.</p>
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+
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</div>
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</div>
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</dd>
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-
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-
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+
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+
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<dt>
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<term>tickTime</term>
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</dt>
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<dd>
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-<p>the length of a single tick, which is the basic time
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- unit used by ZooKeeper, as measured in milliseconds. It is
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- used to regulate heartbeats, and timeouts. For example, the
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- minimum session timeout will be two ticks.</p>
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+<p>the length of a single tick, which is the basic time unit
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+ used by ZooKeeper, as measured in milliseconds. It is used to
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+ regulate heartbeats, and timeouts. For example, the minimum
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+ session timeout will be two ticks.</p>
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</dd>
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-
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-
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+
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</dl>
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-<a name="N10153"></a><a name="sc_advancedConfiguration"></a>
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+<a name="N101CC"></a><a name="sc_advancedConfiguration"></a>
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<h4>Advanced Configuration</h4>
|
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-<p>The configuration settings in the section are optional. You
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- can use them to further fine tune the behaviour of your Zookeeper
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- servers. Some can also be set using Java system properties,
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- generally of the form <em>zookeeper.keyword</em>. The
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- exact system property, when available, is noted below.</p>
|
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|
+<p>The configuration settings in the section are optional. You can
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+ use them to further fine tune the behaviour of your ZooKeeper servers.
|
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+ Some can also be set using Java system properties, generally of the
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+ form <em>zookeeper.keyword</em>. The exact system
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+ property, when available, is noted below.</p>
|
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<dl>
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-
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-
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+
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<dt>
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<term>dataLogDir</term>
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</dt>
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<dd>
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<p>(No Java system property)</p>
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<p>This option will direct the machine to write the
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- transaction log to the <strong>dataLogDir</strong> rather than the <strong>dataDir</strong>. This allows a dedicated log
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- device to be used, and helps avoid competition between logging
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- and snaphots.</p>
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+ transaction log to the <strong>dataLogDir</strong> rather than the <strong>dataDir</strong>. This allows a dedicated log
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+ device to be used, and helps avoid competition between logging
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+ and snaphots.</p>
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<div class="note">
|
|
|
<div class="label">Note</div>
|
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|
<div class="content">
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-
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|
|
-<p>Having a dedicated log device has a large impact on
|
|
|
- throughput and stable latencies. It is highly recommened to
|
|
|
- dedicate a log device and set <strong>dataLogDir</strong> to point to a directory on
|
|
|
- that device, and then make sure to point <strong>dataDir</strong> to a directory
|
|
|
- <em>not</em> residing on that device.</p>
|
|
|
|
|
|
+<p>Having a dedicated log device has a large impact on
|
|
|
+ throughput and stable latencies. It is highly recommened to
|
|
|
+ dedicate a log device and set <strong>dataLogDir</strong> to point to a directory on
|
|
|
+ that device, and then make sure to point <strong>dataDir</strong> to a directory
|
|
|
+ <em>not</em> residing on that device.</p>
|
|
|
+
|
|
|
</div>
|
|
|
</div>
|
|
|
</dd>
|
|
|
-
|
|
|
-
|
|
|
+
|
|
|
+
|
|
|
<dt>
|
|
|
<term>globalOutstandingLimit</term>
|
|
|
</dt>
|
|
|
<dd>
|
|
|
<p>(Java system property: <strong>zookeeper.globalOutstandingLimit.</strong>)</p>
|
|
|
<p>Clients can submit requests faster than ZooKeeper can
|
|
|
- process them, especially if there are a lot of clients. To
|
|
|
- prevent ZooKeeper from running out of memory due to queued
|
|
|
- requests, ZooKeeper will throttle clients so that there is no
|
|
|
- more than globalOutstandingLimit outstanding requests in the
|
|
|
- system. The default limit is 1,000.</p>
|
|
|
+ process them, especially if there are a lot of clients. To
|
|
|
+ prevent ZooKeeper from running out of memory due to queued
|
|
|
+ requests, ZooKeeper will throttle clients so that there is no
|
|
|
+ more than globalOutstandingLimit outstanding requests in the
|
|
|
+ system. The default limit is 1,000.</p>
|
|
|
</dd>
|
|
|
-
|
|
|
-
|
|
|
+
|
|
|
+
|
|
|
<dt>
|
|
|
<term>preAllocSize</term>
|
|
|
</dt>
|
|
|
<dd>
|
|
|
<p>(Java system property: <strong>zookeeper.preAllocSize</strong>)</p>
|
|
|
<p>To avoid seeks ZooKeeper allocates space in the
|
|
|
- transaction log file in blocks of preAllocSize kilobytes. The
|
|
|
- default block size is 64M. One reason for changing the size of
|
|
|
- the blocks is to reduce the block size if snapshots are taken
|
|
|
- more often. (Also, see <strong>snapCount</strong>).</p>
|
|
|
+ transaction log file in blocks of preAllocSize kilobytes. The
|
|
|
+ default block size is 64M. One reason for changing the size of
|
|
|
+ the blocks is to reduce the block size if snapshots are taken
|
|
|
+ more often. (Also, see <strong>snapCount</strong>).</p>
|
|
|
</dd>
|
|
|
|
|
|
-
|
|
|
+
|
|
|
<dt>
|
|
|
<term>snapCount</term>
|
|
|
</dt>
|
|
|
<dd>
|
|
|
<p>(Java system property: <strong>zookeeper.snapCount</strong>)</p>
|
|
|
<p>Clients can submit requests faster than ZooKeeper can
|
|
|
- process them, especially if there are a lot of clients. To
|
|
|
- prevent ZooKeeper from running out of memory due to queued
|
|
|
- requests, ZooKeeper will throttle clients so that there is no
|
|
|
- more than globalOutstandingLimit outstanding requests in the
|
|
|
- system. The default limit is 1,000.ZooKeeper logs transactions
|
|
|
- to a transaction log. After snapCount transactions are written
|
|
|
- to a log file a snapshot is started and a new transaction log
|
|
|
- file is started. The default snapCount is 10,000.</p>
|
|
|
+ process them, especially if there are a lot of clients. To
|
|
|
+ prevent ZooKeeper from running out of memory due to queued
|
|
|
+ requests, ZooKeeper will throttle clients so that there is no
|
|
|
+ more than globalOutstandingLimit outstanding requests in the
|
|
|
+ system. The default limit is 1,000.ZooKeeper logs transactions
|
|
|
+ to a transaction log. After snapCount transactions are written
|
|
|
+ to a log file a snapshot is started and a new transaction log
|
|
|
+ file is started. The default snapCount is 10,000.</p>
|
|
|
</dd>
|
|
|
|
|
|
-
|
|
|
+
|
|
|
<dt>
|
|
|
<term>traceFile</term>
|
|
|
</dt>
|
|
|
<dd>
|
|
|
<p>(Java system property: <strong>requestTraceFile</strong>)</p>
|
|
|
-<p>If this option is defined, requests will be will logged
|
|
|
- to a trace file named traceFile.year.month.day. Use of this
|
|
|
- option provides useful debugging information, but will impact
|
|
|
- performance. (Note: The system property has no zookeeper
|
|
|
- prefix, and the configuration variable name is different from
|
|
|
- the system property. Yes - it's not consistent, and it's
|
|
|
- annoying.)</p>
|
|
|
+<p>If this option is defined, requests will be will logged to
|
|
|
+ a trace file named traceFile.year.month.day. Use of this option
|
|
|
+ provides useful debugging information, but will impact
|
|
|
+ performance. (Note: The system property has no zookeeper prefix,
|
|
|
+ and the configuration variable name is different from the system
|
|
|
+ property. Yes - it's not consistent, and it's annoying.)</p>
|
|
|
</dd>
|
|
|
-
|
|
|
-
|
|
|
+
|
|
|
</dl>
|
|
|
-<a name="N101B3"></a><a name="sc_clusterOptions"></a>
|
|
|
+<a name="N1022C"></a><a name="sc_clusterOptions"></a>
|
|
|
<h4>Cluster Options</h4>
|
|
|
<p>The options in this section are designed for use in quorums --
|
|
|
- that is, when deploying clusters of servers.</p>
|
|
|
+ that is, when deploying clusters of servers.</p>
|
|
|
<dl>
|
|
|
-
|
|
|
+
|
|
|
<dt>
|
|
|
-<term>electionAlg:</term>
|
|
|
+<term>electionAlg</term>
|
|
|
</dt>
|
|
|
<dd>
|
|
|
<p>(No Java system property)</p>
|
|
|
-<p>Election implementation to use. A value of "0"
|
|
|
- corresponds to the original UDP-based version, "1" corresponds
|
|
|
- to the non-authenticated UDP-based version of fast leader
|
|
|
- election, "2" corresponds to the authenticated UDP-based
|
|
|
- version of fast leader election, and "3" corresponds to
|
|
|
- TCP-based version of fast leader election</p>
|
|
|
+<p>Election implementation to use. A value of "0" corresponds
|
|
|
+ to the original UDP-based version, "1" corresponds to the
|
|
|
+ non-authenticated UDP-based version of fast leader election, "2"
|
|
|
+ corresponds to the authenticated UDP-based version of fast
|
|
|
+ leader election, and "3" corresponds to TCP-based version of
|
|
|
+ fast leader election</p>
|
|
|
</dd>
|
|
|
|
|
|
-
|
|
|
+
|
|
|
<dt>
|
|
|
<term>electionPort</term>
|
|
|
</dt>
|
|
|
<dd>
|
|
|
<p>(No Java system property)</p>
|
|
|
<p>Port used for leader election. It is only used when the
|
|
|
- election algorithm is not "0". When the election algorithm is
|
|
|
- "0" a UDP port with the same port number as the port listed in
|
|
|
- the <strong>server.num</strong> option will be
|
|
|
- used.</p>
|
|
|
+ election algorithm is not "0". When the election algorithm is
|
|
|
+ "0" a UDP port with the same port number as the port listed in
|
|
|
+ the <strong>server.num</strong> option will be
|
|
|
+ used.</p>
|
|
|
</dd>
|
|
|
|
|
|
-
|
|
|
+
|
|
|
<dt>
|
|
|
<term>initLimit</term>
|
|
|
</dt>
|
|
|
<dd>
|
|
|
<p>(No Java system property)</p>
|
|
|
<p>Amount of time, in ticks (see <a href="#id_tickTime">tickTime</a>), to allow followers to
|
|
|
- connect and sync to a leader. Increased this value as needed,
|
|
|
- if the amount of data managed by ZooKeeper is large.</p>
|
|
|
+ connect and sync to a leader. Increased this value as needed, if
|
|
|
+ the amount of data managed by ZooKeeper is large.</p>
|
|
|
</dd>
|
|
|
|
|
|
-
|
|
|
+
|
|
|
<dt>
|
|
|
<term>leaderServes</term>
|
|
|
</dt>
|
|
|
<dd>
|
|
|
<p>(Java system property: zookeeper.<strong>leaderServes</strong>)</p>
|
|
|
-<p>Leader accepts client connections. Default value is
|
|
|
- "yes". The leader machine coordinates updates. For higher
|
|
|
- update throughput at thes slight expense of read throughput
|
|
|
- the leader can be configured to not accept clients and focus
|
|
|
- on coordination. The default to this option is yes, which
|
|
|
- means that a leader will accept client connections.
|
|
|
- </p>
|
|
|
+<p>Leader accepts client connections. Default value is "yes".
|
|
|
+ The leader machine coordinates updates. For higher update
|
|
|
+ throughput at thes slight expense of read throughput the leader
|
|
|
+ can be configured to not accept clients and focus on
|
|
|
+ coordination. The default to this option is yes, which means
|
|
|
+ that a leader will accept client connections.</p>
|
|
|
<div class="note">
|
|
|
<div class="label">Note</div>
|
|
|
<div class="content">
|
|
|
-
|
|
|
-<p>Turning on leader selection is highly recommended when
|
|
|
- you have more than three Zookeeper servers in a
|
|
|
- quorum.</p>
|
|
|
|
|
|
+<p>Turning on leader selection is highly recommended when
|
|
|
+ you have more than three ZooKeeper servers in a quorum.</p>
|
|
|
+
|
|
|
</div>
|
|
|
</div>
|
|
|
</dd>
|
|
|
|
|
|
-
|
|
|
+
|
|
|
<dt>
|
|
|
<term>server.x=[hostname]:nnnn, etc</term>
|
|
|
</dt>
|
|
|
<dd>
|
|
|
<p>(No Java system property)</p>
|
|
|
-<p>servers making up the Zookeeper quorum. When the server
|
|
|
- starts up, it determines which server it is by looking for the
|
|
|
- file <span class="codefrag filename">myid</span> in the data directory. That file contains the
|
|
|
- server number, in ASCII, and it should match <strong>x</strong> in <strong>server.x</strong> in the left hand side of this
|
|
|
- setting.</p>
|
|
|
-<p>The list of servers that make up ZooKeeper servers that
|
|
|
- is used by the clients must match the list of ZooKeeper
|
|
|
- servers that each ZooKeeper server has.</p>
|
|
|
-<p>The port numbers <strong>nnnn</strong>
|
|
|
- in this setting are the <em>electionPort</em>
|
|
|
- numbers of the servers (as opposed to clientPorts).
|
|
|
- If you want to test multiple servers on a single
|
|
|
- machine, the individual choices of electionPort for each
|
|
|
- server can be defined in each server's config files using the
|
|
|
- line electionPort=xxxx to avoid clashes.</p>
|
|
|
+<p>servers making up the ZooKeeper quorum. When the server
|
|
|
+ starts up, it determines which server it is by looking for the
|
|
|
+ file <span class="codefrag filename">myid</span> in the data directory. That file
|
|
|
+ contains the server number, in ASCII, and it should match
|
|
|
+ <strong>x</strong> in <strong>server.x</strong> in the left hand side of this
|
|
|
+ setting.</p>
|
|
|
+<p>The list of servers that make up ZooKeeper servers that is
|
|
|
+ used by the clients must match the list of ZooKeeper servers
|
|
|
+ that each ZooKeeper server has.</p>
|
|
|
+<p>The port numbers <strong>nnnn</strong> in
|
|
|
+ this setting are the <em>electionPort</em> numbers
|
|
|
+ of the servers (as opposed to clientPorts). If you want to test
|
|
|
+ multiple servers on a single machine, the individual choices of
|
|
|
+ electionPort for each server can be defined in each server's
|
|
|
+ config files using the line electionPort=xxxx to avoid
|
|
|
+ clashes.</p>
|
|
|
</dd>
|
|
|
|
|
|
-
|
|
|
+
|
|
|
<dt>
|
|
|
<term>syncLimit</term>
|
|
|
</dt>
|
|
|
<dd>
|
|
|
<p>(No Java system property)</p>
|
|
|
-<p>Amount of time, in ticks (see <a href="#id_tickTime">tickTime</a>), to allow followers to
|
|
|
- sync with ZooKeeper. If followers fall too far behind a
|
|
|
- leader, they will be dropped.</p>
|
|
|
+<p>Amount of time, in ticks (see <a href="#id_tickTime">tickTime</a>), to allow followers to sync
|
|
|
+ with ZooKeeper. If followers fall too far behind a leader, they
|
|
|
+ will be dropped.</p>
|
|
|
</dd>
|
|
|
-
|
|
|
+
|
|
|
</dl>
|
|
|
<p></p>
|
|
|
-<a name="N1021F"></a><a name="Unsafe+Options"></a>
|
|
|
+<a name="N10298"></a><a name="Unsafe+Options"></a>
|
|
|
<h4>Unsafe Options</h4>
|
|
|
-<p>The following options can be useful, but be careful when you
|
|
|
- use them. The risk of each is explained along with the explanation
|
|
|
- of what the variable does.</p>
|
|
|
+<p>The following options can be useful, but be careful when you use
|
|
|
+ them. The risk of each is explained along with the explanation of what
|
|
|
+ the variable does.</p>
|
|
|
<dl>
|
|
|
-
|
|
|
-
|
|
|
+
|
|
|
<dt>
|
|
|
<term>forceSync</term>
|
|
|
</dt>
|
|
|
<dd>
|
|
|
<p>(Java system property: <strong>zookeeper.forceSync</strong>)</p>
|
|
|
-<p>Requires updates to be synced to media of the
|
|
|
- transaction log before finishing processing the update. If
|
|
|
- this option is set to no, ZooKeeper will not require updates
|
|
|
- to be synced to the media.</p>
|
|
|
+<p>Requires updates to be synced to media of the transaction
|
|
|
+ log before finishing processing the update. If this option is
|
|
|
+ set to no, ZooKeeper will not require updates to be synced to
|
|
|
+ the media.</p>
|
|
|
</dd>
|
|
|
|
|
|
-
|
|
|
+
|
|
|
<dt>
|
|
|
<term>jute.maxbuffer:</term>
|
|
|
</dt>
|
|
|
<dd>
|
|
|
<p>(Java system property:<strong>
|
|
|
- jute.maxbuffer</strong>)</p>
|
|
|
+ jute.maxbuffer</strong>)</p>
|
|
|
<p>This option can only be set as a Java system property.
|
|
|
- There is no zookeeper prefix on it. It specifies the maximum
|
|
|
- size of the data that can be stored in a znode. The default is
|
|
|
- 0xfffff, or just under 1M. If this option is changed, the
|
|
|
- system property must be set on all servers and clients
|
|
|
- otherwise problems will arise. This is really a sanity check.
|
|
|
- ZooKeeper is designed to store data on the order of kilobytes
|
|
|
- in size.</p>
|
|
|
+ There is no zookeeper prefix on it. It specifies the maximum
|
|
|
+ size of the data that can be stored in a znode. The default is
|
|
|
+ 0xfffff, or just under 1M. If this option is changed, the system
|
|
|
+ property must be set on all servers and clients otherwise
|
|
|
+ problems will arise. This is really a sanity check. ZooKeeper is
|
|
|
+ designed to store data on the order of kilobytes in size.</p>
|
|
|
</dd>
|
|
|
-
|
|
|
-
|
|
|
+
|
|
|
+
|
|
|
<dt>
|
|
|
<term>skipACL</term>
|
|
|
</dt>
|
|
|
<dd>
|
|
|
<p>(Java system property: <strong>zookeeper.skipACL</strong>)</p>
|
|
|
-<p>Skips ACL checks.
|
|
|
- This results in a boost in throughput, but opens up full
|
|
|
- access to the data tree to everyone.</p>
|
|
|
+<p>Skips ACL checks. This results in a boost in throughput,
|
|
|
+ but opens up full access to the data tree to everyone.</p>
|
|
|
</dd>
|
|
|
-
|
|
|
-
|
|
|
-
|
|
|
+
|
|
|
</dl>
|
|
|
-<a name="N10251"></a><a name="sc_zkCommands"></a>
|
|
|
-<h3 class="h4">Zookeeper Commands: The Four Letter Words</h3>
|
|
|
-<p>Zookeeper responds to a small set of commands. Each command is composed of
|
|
|
- four letters. You issue the commands to Zookeeper via telnet or nc, at
|
|
|
- the client port.</p>
|
|
|
+<a name="N102CA"></a><a name="sc_zkCommands"></a>
|
|
|
+<h3 class="h4">ZooKeeper Commands: The Four Letter Words</h3>
|
|
|
+<p>ZooKeeper responds to a small set of commands. Each command is
|
|
|
+ composed of four letters. You issue the commands to ZooKeeper via telnet
|
|
|
+ or nc, at the client port.</p>
|
|
|
<dl>
|
|
|
-
|
|
|
-
|
|
|
+
|
|
|
<dt>
|
|
|
<term>dump</term>
|
|
|
</dt>
|
|
|
<dd>
|
|
|
<p>Lists the outstanding sessions and ephemeral nodes. This
|
|
|
- only works on the leader.</p>
|
|
|
+ only works on the leader.</p>
|
|
|
</dd>
|
|
|
-
|
|
|
-
|
|
|
+
|
|
|
+
|
|
|
<dt>
|
|
|
<term>kill</term>
|
|
|
</dt>
|
|
|
<dd>
|
|
|
-<p>Shuts down the server. This must be issued from the
|
|
|
- machine the Zookeeper server is running on.</p>
|
|
|
+<p>Shuts down the server. This must be issued from the machine
|
|
|
+ the ZooKeeper server is running on.</p>
|
|
|
</dd>
|
|
|
-
|
|
|
-
|
|
|
+
|
|
|
+
|
|
|
<dt>
|
|
|
<term>ruok</term>
|
|
|
</dt>
|
|
|
<dd>
|
|
|
-<p>Tests if server is running in a non-error state. The
|
|
|
- server will respond with imok if it is running. Otherwise it
|
|
|
- will not respond at all.</p>
|
|
|
+<p>Tests if server is running in a non-error state. The server
|
|
|
+ will respond with imok if it is running. Otherwise it will not
|
|
|
+ respond at all.</p>
|
|
|
</dd>
|
|
|
|
|
|
-
|
|
|
+
|
|
|
<dt>
|
|
|
<term>stat</term>
|
|
|
</dt>
|
|
|
<dd>
|
|
|
<p>Lists statistics about performance and connected
|
|
|
- clients.</p>
|
|
|
+ clients.</p>
|
|
|
</dd>
|
|
|
-
|
|
|
+
|
|
|
</dl>
|
|
|
<p>Here's an example of the <strong>ruok</strong>
|
|
|
- command:</p>
|
|
|
-<p>
|
|
|
-<span class="codefrag computeroutput">$ echo ruok | nc 127.0.0.1 5111
|
|
|
-
|
|
|
-imok</span>
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|
-
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|
-</p>
|
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|
-<a name="N10286"></a><a name="sc_monitoring"></a>
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|
|
-<h3 class="h4">Monitoring</h3>
|
|
|
-<p>
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|
|
-<em>[tbd]</em>
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|
-</p>
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|
-<a name="N10291"></a><a name="sc_dataFileManagement"></a>
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|
|
+ command:</p>
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|
|
+<pre class="code">$ echo ruok | nc 127.0.0.1 5111
|
|
|
+imok
|
|
|
+</pre>
|
|
|
+<a name="N102FC"></a><a name="sc_dataFileManagement"></a>
|
|
|
<h3 class="h4">Data File Management</h3>
|
|
|
<p>ZooKeeper stores its data in a data directory and its transaction
|
|
|
log in a transaction log directory. By default these two directories are
|
|
|
@@ -881,7 +970,7 @@ imok</span>
|
|
|
transaction log files in a separate directory than the data files.
|
|
|
Throughput increases and latency decreases when transaction logs reside
|
|
|
on a dedicated log devices.</p>
|
|
|
-<a name="N1029A"></a><a name="The+Data+Directory"></a>
|
|
|
+<a name="N10305"></a><a name="The+Data+Directory"></a>
|
|
|
<h4>The Data Directory</h4>
|
|
|
<p>This directory has two files in it:</p>
|
|
|
<ul>
|
|
|
@@ -927,14 +1016,14 @@ imok</span>
|
|
|
idempotent nature of its updates. By replaying the transaction log
|
|
|
against fuzzy snapshots ZooKeeper gets the state of the system at the
|
|
|
end of the log.</p>
|
|
|
-<a name="N102D6"></a><a name="The+Log+Directory"></a>
|
|
|
+<a name="N10341"></a><a name="The+Log+Directory"></a>
|
|
|
<h4>The Log Directory</h4>
|
|
|
<p>The Log Directory contains the ZooKeeper transaction logs.
|
|
|
Before any update takes place, ZooKeeper ensures that the transaction
|
|
|
that represents the update is written to non-volatile storage. A new
|
|
|
log file is started each time a snapshot is begun. The log file's
|
|
|
suffix is the first zxid written to that log.</p>
|
|
|
-<a name="N102E0"></a><a name="File+Management"></a>
|
|
|
+<a name="N1034B"></a><a name="File+Management"></a>
|
|
|
<h4>File Management</h4>
|
|
|
<p>The format of snapshot and log files does not change between
|
|
|
standalone ZooKeeper servers and different configurations of
|
|
|
@@ -951,7 +1040,7 @@ imok</span>
|
|
|
needs the latest complete fuzzy snapshot and the log files from the
|
|
|
start of that snapshot. The PurgeTxnLog utility implements a simple
|
|
|
retention policy that administrators can use.</p>
|
|
|
-<a name="N102F1"></a><a name="sc_commonProblems"></a>
|
|
|
+<a name="N1035C"></a><a name="sc_commonProblems"></a>
|
|
|
<h3 class="h4">Things to Avoid</h3>
|
|
|
<p>Here are some common problems you can avoid by configuring
|
|
|
ZooKeeper correctly:</p>
|
|
|
@@ -961,7 +1050,7 @@ imok</span>
|
|
|
<term>inconsistent lists of servers</term>
|
|
|
</dt>
|
|
|
<dd>
|
|
|
-<p>The list of Zookeeper servers used by the clients must match
|
|
|
+<p>The list of ZooKeeper servers used by the clients must match
|
|
|
the list of ZooKeeper servers that each ZooKeeper server has.
|
|
|
Things work okay if the client list is a subset of the real list,
|
|
|
but things will really act strange if clients have a list of
|
|
|
@@ -976,7 +1065,7 @@ imok</span>
|
|
|
</dt>
|
|
|
<dd>
|
|
|
<p>The most performance critical part of ZooKeeper is the
|
|
|
- transaction log. Zookeeper syncs transactions to media before it
|
|
|
+ transaction log. ZooKeeper syncs transactions to media before it
|
|
|
returns a response. A dedicated transaction log device is key to
|
|
|
consistent good performance. Putting the log on a busy device will
|
|
|
adversely effect performance. If you only have one storage device,
|
|
|
@@ -991,7 +1080,7 @@ imok</span>
|
|
|
<dd>
|
|
|
<p>You should take special care to set your Java max heap size
|
|
|
correctly. In particular, you should not create a situation in
|
|
|
- which Zookeeper swaps to disk. The disk is death to ZooKeeper.
|
|
|
+ which ZooKeeper swaps to disk. The disk is death to ZooKeeper.
|
|
|
Everything is ordered, so if processing one request swaps the
|
|
|
disk, all other queued requests will probably do the same. the
|
|
|
disk. DON'T SWAP.</p>
|
|
|
@@ -1005,7 +1094,7 @@ imok</span>
|
|
|
</dd>
|
|
|
|
|
|
</dl>
|
|
|
-<a name="N10315"></a><a name="sc_bestPractices"></a>
|
|
|
+<a name="N10380"></a><a name="sc_bestPractices"></a>
|
|
|
<h3 class="h4">Best Practices</h3>
|
|
|
<p>For best results, take note of the following list of good
|
|
|
Zookeeper practices. <em>[tbd...]</em>
|
Patrick D. Hunt