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@@ -273,7 +273,7 @@ document.write("Last Published: " + document.lastModified);
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production environment.</p>
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<a name="N10034"></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 1.6 or greater, as group of hosts
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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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@@ -283,7 +283,7 @@ document.write("Last Published: " + document.lastModified);
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<p>For reliable ZooKeeper service, you should deploy ZooKeeper in a
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cluster known as a <em>quorum</em>. As long as a majority
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of the quorum are up, the service will be available. Because Zookeeper
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- requires a majority <remark>[tbd: why?]</remark>, it is best to use an
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+ requires a majority, it is best to use an
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odd number of machines. For example, with four machines ZooKeeper can
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only handle the failure of a single machine; if two machines fail, the
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remaining two machines do not constitute a majority. However, with five
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@@ -298,8 +298,7 @@ document.write("Last Published: " + document.lastModified);
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<p>Install the Java JDK:</p>
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-<pre class="code">$yinst -i jdk-1.6.0.00_3 -br test <remark>[y! prop - replace with open equiv]</remark>
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-</pre>
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+<pre class="code">$yinst -i jdk-1.6.0.00_3 -br test </pre>
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</li>
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@@ -310,10 +309,7 @@ document.write("Last Published: " + document.lastModified);
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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. <remark>[tbd:
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- where would they do this? Environment variable,
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- etc?]</remark>
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-</p>
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+ - use a maximum heap size of 3GB for a 4GB machine.</p>
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</li>
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@@ -323,8 +319,7 @@ document.write("Last Published: " + document.lastModified);
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<p>Install the Zookeeper Server Package:</p>
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-<pre class="code">$ yinst install -nostart zookeeper_server <remark>[Y! prop - replace with open eq]</remark>
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-</pre>
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+<pre class="code">$ yinst install -nostart zookeeper_server </pre>
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</li>
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@@ -388,9 +383,7 @@ server.3=zoo3:2888</pre>
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<li>
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<p>In Java, you can run the following command to execute
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- simple operations:<remark> [tbd: also, maybe give some of those
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- simple operations?]</remark>
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-</p>
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+ simple operations:</p>
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<pre class="code">$ java -cp zookeeper.jar:java/lib/log4j-1.2.15.jar:conf \
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@@ -421,8 +414,7 @@ server.3=zoo3:2888</pre>
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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. <remark>[tbd: again, sample
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- operations?]</remark> To connect to Zookeeper with the multithreaded
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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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@@ -431,7 +423,7 @@ server.3=zoo3:2888</pre>
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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="N100C0"></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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@@ -450,7 +442,7 @@ server.3=zoo3:2888</pre>
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</div>
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-<a name="N100EF"></a><a name="Administration"></a>
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+<a name="N100E1"></a><a name="Administration"></a>
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<h2 class="h3">Administration</h2>
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<div class="section">
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<p>This chapter contains information about running and maintaining
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@@ -502,17 +494,15 @@ server.3=zoo3:2888</pre>
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</ul>
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</p>
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-<a name="N10122"></a><a name="sc_configuration"></a>
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+<a name="N10114"></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.<remark> [tbd: reformat in
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- standard form, with legal values, etc]</remark>
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-</p>
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-<a name="N1012D"></a><a name="sc_minimumConfiguration"></a>
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+ different configuration files match.</p>
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+<a name="N1011D"></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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@@ -561,7 +551,7 @@ server.3=zoo3:2888</pre>
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</dl>
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-<a name="N10154"></a><a name="sc_advancedConfiguration"></a>
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+<a name="N10144"></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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@@ -650,13 +640,12 @@ server.3=zoo3:2888</pre>
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performance. (Note: The system property has no zookeeper
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prefix, and the configuration variable name is different from
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the system property. Yes - it's not consistent, and it's
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- annoying.<remark> [tbd: is there any explanation for
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- this?]</remark>)</p>
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+ annoying.)</p>
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</dd>
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</dl>
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-<a name="N101B7"></a><a name="sc_clusterOptions"></a>
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+<a name="N101A4"></a><a name="sc_clusterOptions"></a>
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<h4>Cluster Options</h4>
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<p>The options in this section are designed for use in quorums --
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that is, when deploying clusters of servers.</p>
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@@ -685,9 +674,7 @@ server.3=zoo3:2888</pre>
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election algorithm is not "0". When the election algorithm is
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"0" a UDP port with the same port number as the port listed in
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the <strong>server.num</strong> option will be
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- used. <remark>[tbd: should that be <strong>server.id</strong>? Also, why isn't server.id
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- documented anywhere?]</remark>
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|
-</p>
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+ used.</p>
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</dd>
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@@ -713,9 +700,7 @@ server.3=zoo3:2888</pre>
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the leader can be configured to not accept clients and focus
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on coordination. The default to this option is yes, which
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means that a leader will accept client connections.
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- <remark>[tbd: how do you specifiy which server is the
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- leader?]</remark>
|
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|
-</p>
|
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+ </p>
|
|
|
<div class="note">
|
|
|
<div class="label">Note</div>
|
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<div class="content">
|
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@@ -736,9 +721,7 @@ server.3=zoo3:2888</pre>
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<p>(No Java system property)</p>
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<p>servers making up the Zookeeper quorum. When the server
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starts up, it determines which server it is by looking for the
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- file <span class="codefrag filename">myid</span> in the data directory.<remark>
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|
- [tdb: should we mention somewhere about creating this file,
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- myid, in the setup procedure?]</remark> That file contains the
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+ file <span class="codefrag filename">myid</span> in the data directory. That file contains the
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server number, in ASCII, and it should match <strong>x</strong> in <strong>server.x</strong> in the left hand side of this
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setting.</p>
|
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|
<p>The list of servers that make up ZooKeeper servers that
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@@ -747,9 +730,7 @@ server.3=zoo3:2888</pre>
|
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|
<p>The port numbers <strong>nnnn</strong>
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|
|
in this setting are the <em>electionPort</em>
|
|
|
numbers of the servers (as opposed to clientPorts).
|
|
|
- <remark>[tbd: is the next sentence explanation an of what the
|
|
|
- election port or is it a description of a special case?]
|
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|
- </remark>If you want to test multiple servers on a single
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+ If you want to test multiple servers on a single
|
|
|
machine, the individual choices of electionPort for each
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|
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server can be defined in each server's config files using the
|
|
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line electionPort=xxxx to avoid clashes.</p>
|
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@@ -763,15 +744,12 @@ server.3=zoo3:2888</pre>
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<p>(No Java system property)</p>
|
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<p>Amount of time, in ticks (see <a href="#id_tickTime">tickTime</a>), to allow followers to
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|
|
sync with ZooKeeper. If followers fall too far behind a
|
|
|
- leader, they will be dropped. <remark>[tbd: is this a correct
|
|
|
- rewording: if followers fall beyond this limit, they are
|
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- dropped?]</remark>
|
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|
-</p>
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|
+ leader, they will be dropped.</p>
|
|
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</dd>
|
|
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|
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</dl>
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|
<p></p>
|
|
|
-<a name="N10232"></a><a name="Unsafe+Options"></a>
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|
|
+<a name="N10210"></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
|
|
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@@ -787,9 +765,7 @@ server.3=zoo3:2888</pre>
|
|
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<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. <remark>[tbd: useful because...,
|
|
|
- dangerous because...]</remark>
|
|
|
-</p>
|
|
|
+ to be synced to the media.</p>
|
|
|
</dd>
|
|
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|
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|
|
|
|
@@ -815,7 +791,7 @@ server.3=zoo3:2888</pre>
|
|
|
</dt>
|
|
|
<dd>
|
|
|
<p>(Java system property: <strong>zookeeper.skipACL</strong>)</p>
|
|
|
-<p>Skips ACL checks. <remark>[tbd: when? where?]</remark>
|
|
|
+<p>Skips ACL checks.
|
|
|
This results in a boost in throughput, but opens up full
|
|
|
access to the data tree to everyone.</p>
|
|
|
</dd>
|
|
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@@ -823,7 +799,7 @@ server.3=zoo3:2888</pre>
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|
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|
|
|
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|
|
</dl>
|
|
|
-<a name="N10269"></a><a name="sc_zkCommands"></a>
|
|
|
+<a name="N10242"></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
|
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@@ -874,16 +850,10 @@ server.3=zoo3:2888</pre>
|
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|
imok
|
|
|
</pre>
|
|
|
-<a name="N1029B"></a><a name="sc_monitoring"></a>
|
|
|
+<a name="N10274"></a><a name="sc_monitoring"></a>
|
|
|
<h3 class="h4">Monitoring</h3>
|
|
|
-<p>
|
|
|
-<remark>[tbd: Patrick, Ben, et al: I believe the Message Broker
|
|
|
- team does perform routine monitoring of Zookeeper. But I might be
|
|
|
- wrong. To your knowledge, is there any monitoring of a Zookeeper
|
|
|
- deployment that will a Zookeeper sys admin will want to do, outside of
|
|
|
- Yahoo?]</remark>
|
|
|
-</p>
|
|
|
-<a name="N102A6"></a><a name="sc_dataFileManagement"></a>
|
|
|
+<remark>[tbd]</remark>
|
|
|
+<a name="N1027E"></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
|
|
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@@ -891,7 +861,7 @@ imok
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|
|
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="N102AF"></a><a name="The+Data+Directory"></a>
|
|
|
+<a name="N10287"></a><a name="The+Data+Directory"></a>
|
|
|
<h4>The Data Directory</h4>
|
|
|
<p>This directory has two files in it:</p>
|
|
|
<ul>
|
|
|
@@ -937,14 +907,14 @@ imok
|
|
|
idempotent nature of its updates. By replaying the transaction log
|
|
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against fuzzy snapshots ZooKeeper gets the state of the system at the
|
|
|
end of the log.</p>
|
|
|
-<a name="N102EB"></a><a name="The+Log+Directory"></a>
|
|
|
+<a name="N102C3"></a><a name="The+Log+Directory"></a>
|
|
|
<h4>The Log Directory</h4>
|
|
|
<p>The Log Directory contains the ZooKeeper transaction logs.
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|
|
Before any update takes place, ZooKeeper ensures that the transaction
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|
|
that represents the update is written to non-volatile storage. A new
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|
|
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="N102F5"></a><a name="File+Management"></a>
|
|
|
+<a name="N102CD"></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
|
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@@ -961,7 +931,7 @@ imok
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|
|
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="N10306"></a><a name="sc_commonProblems"></a>
|
|
|
+<a name="N102DE"></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>
|
|
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@@ -977,9 +947,7 @@ imok
|
|
|
but things will really act strange if clients have a list of
|
|
|
ZooKeeper servers that are in different ZooKeeper clusters. Also,
|
|
|
the server lists in each Zookeeper server configuration file
|
|
|
- should be consistent with one another. <remark>[tbd: I'm assuming
|
|
|
- this last part is true. Is it?]</remark>
|
|
|
-</p>
|
|
|
+ should be consistent with one another.</p>
|
|
|
</dd>
|
|
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|
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@@ -1017,12 +985,10 @@ imok
|
|
|
</dd>
|
|
|
|
|
|
</dl>
|
|
|
-<a name="N1032C"></a><a name="sc_bestPractices"></a>
|
|
|
+<a name="N10302"></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. <remark>[tbd: I just threw this section in. Do we
|
|
|
- have list that is is different from the "things to avoid"? If not, I can
|
|
|
- easily remove this section.]</remark>
|
|
|
+ Zookeeper practices. <remark>[tbd...]</remark>
|
|
|
</p>
|
|
|
</div>
|
|
|
|
Patrick D. Hunt