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  102. <h1>Hadoop Cluster Setup</h1>
  103. <div id="minitoc-area">
  104. <ul class="minitoc">
  105. <li>
  106. <a href="#Purpose">Purpose</a>
  107. </li>
  108. <li>
  109. <a href="#Pre-requisites">Pre-requisites</a>
  110. </li>
  111. <li>
  112. <a href="#Installation">Installation</a>
  113. </li>
  114. <li>
  115. <a href="#Configuration">Configuration</a>
  116. <ul class="minitoc">
  117. <li>
  118. <a href="#Configuration+Files">Configuration Files</a>
  119. </li>
  120. <li>
  121. <a href="#Site+Configuration">Site Configuration</a>
  122. <ul class="minitoc">
  123. <li>
  124. <a href="#Configuring+the+Environment+of+the+Hadoop+Daemons">Configuring the Environment of the Hadoop Daemons</a>
  125. </li>
  126. <li>
  127. <a href="#Configuring+the+Hadoop+Daemons">Configuring the Hadoop Daemons</a>
  128. </li>
  129. <li>
  130. <a href="#Slaves">Slaves</a>
  131. </li>
  132. <li>
  133. <a href="#Logging">Logging</a>
  134. </li>
  135. </ul>
  136. </li>
  137. </ul>
  138. </li>
  139. <li>
  140. <a href="#Hadoop+Startup">Hadoop Startup</a>
  141. </li>
  142. <li>
  143. <a href="#Hadoop+Shutdown">Hadoop Shutdown</a>
  144. </li>
  145. </ul>
  146. </div>
  147. <a name="N1000C"></a><a name="Purpose"></a>
  148. <h2 class="h3">Purpose</h2>
  149. <div class="section">
  150. <p>This document describes how to install, configure and manage non-trivial
  151. Hadoop clusters ranging from a few nodes to extremely large clusters with
  152. thousands of nodes.</p>
  153. <p>If you are looking to install Hadoop on a single machine to play
  154. with it, you can find relevant details <a href="quickstart.html">here</a>.
  155. </p>
  156. </div>
  157. <a name="N1001D"></a><a name="Pre-requisites"></a>
  158. <h2 class="h3">Pre-requisites</h2>
  159. <div class="section">
  160. <ol>
  161. <li>
  162. Make sure all <a href="quickstart.html#PreReqs">requisite</a> software
  163. is installed on all nodes in your cluster.
  164. </li>
  165. <li>
  166. <a href="quickstart.html#Download">Get</a> the Hadoop software.
  167. </li>
  168. </ol>
  169. </div>
  170. <a name="N10035"></a><a name="Installation"></a>
  171. <h2 class="h3">Installation</h2>
  172. <div class="section">
  173. <p>Installing a Hadoop cluster typically involves unpacking the software
  174. on all the machines in the cluster.</p>
  175. <p>Typically one machine in the cluster is designated as the
  176. <span class="codefrag">NameNode</span> and another machine the as <span class="codefrag">JobTracker</span>,
  177. exclusively. These are the <em>masters</em>. The rest of the machines in
  178. the cluster act as both <span class="codefrag">DataNode</span> <em>and</em>
  179. <span class="codefrag">TaskTracker</span>. These are the <em>slaves</em>.</p>
  180. <p>The root of the distribution is referred to as
  181. <span class="codefrag">HADOOP_HOME</span>. All machines in the cluster usually have the same
  182. <span class="codefrag">HADOOP_HOME</span> path.</p>
  183. </div>
  184. <a name="N10060"></a><a name="Configuration"></a>
  185. <h2 class="h3">Configuration</h2>
  186. <div class="section">
  187. <p>The following sections describe how to configure a Hadoop cluster.</p>
  188. <a name="N10069"></a><a name="Configuration+Files"></a>
  189. <h3 class="h4">Configuration Files</h3>
  190. <p>Hadoop configuration is driven by two important configuration files
  191. found in the <span class="codefrag">conf/</span> directory of the distribution:</p>
  192. <ol>
  193. <li>
  194. <a href="http://lucene.apache.org/hadoop/hadoop-default.html">hadoop-default.xml</a> - Read-only
  195. default configuration.
  196. </li>
  197. <li>
  198. <em>hadoop-site.xml</em> - Site-specific configuration.
  199. </li>
  200. </ol>
  201. <p>To learn more about how the Hadoop framework is controlled by these
  202. configuration files, look
  203. <a href="api/org/apache/hadoop/conf/Configuration.html">here</a>.</p>
  204. <p>Additionally, you can control the Hadoop scripts found in the
  205. <span class="codefrag">bin/</span> directory of the distribution, by setting site-specific
  206. values via the <span class="codefrag">conf/hadoop-env.sh</span>.</p>
  207. <a name="N10096"></a><a name="Site+Configuration"></a>
  208. <h3 class="h4">Site Configuration</h3>
  209. <p>To configure the the Hadoop cluster you will need to configure the
  210. <em>environment</em> in which the Hadoop daemons execute as well as
  211. the <em>configuration parameters</em> for the Hadoop daemons.</p>
  212. <p>The Hadoop daemons are <span class="codefrag">NameNode</span>/<span class="codefrag">DataNode</span>
  213. and <span class="codefrag">JobTracker</span>/<span class="codefrag">TaskTracker</span>.</p>
  214. <a name="N100B4"></a><a name="Configuring+the+Environment+of+the+Hadoop+Daemons"></a>
  215. <h4>Configuring the Environment of the Hadoop Daemons</h4>
  216. <p>Administrators should use the <span class="codefrag">conf/hadoop-env.sh</span> script
  217. to do site-specific customization of the Hadoop daemons' process
  218. environment.</p>
  219. <p>At the very least you should specify the
  220. <span class="codefrag">JAVA_HOME</span> so that it is correctly defined on each
  221. remote node.</p>
  222. <p>Other useful configuration parameters that you can customize
  223. include:</p>
  224. <ul>
  225. <li>
  226. <span class="codefrag">HADOOP_LOG_DIR</span> - The directory where the daemons'
  227. log files are stored. They are automatically created if they don't
  228. exist.
  229. </li>
  230. <li>
  231. <span class="codefrag">HADOOP_HEAPSIZE</span> - The maximum amount of heapsize
  232. to use, in MB e.g. <span class="codefrag">2000MB</span>.
  233. </li>
  234. </ul>
  235. <a name="N100DC"></a><a name="Configuring+the+Hadoop+Daemons"></a>
  236. <h4>Configuring the Hadoop Daemons</h4>
  237. <p>This section deals with important parameters to be specified in the
  238. <span class="codefrag">conf/hadoop-site.xml</span> for the Hadoop cluster.</p>
  239. <table class="ForrestTable" cellspacing="1" cellpadding="4">
  240. <tr>
  241. <th colspan="1" rowspan="1">Parameter</th>
  242. <th colspan="1" rowspan="1">Value</th>
  243. <th colspan="1" rowspan="1">Notes</th>
  244. </tr>
  245. <tr>
  246. <td colspan="1" rowspan="1">fs.default.name</td>
  247. <td colspan="1" rowspan="1">Hostname or IP address of <span class="codefrag">NameNode</span>.</td>
  248. <td colspan="1" rowspan="1"><em>host:port</em> pair.</td>
  249. </tr>
  250. <tr>
  251. <td colspan="1" rowspan="1">mapred.job.tracker</td>
  252. <td colspan="1" rowspan="1">Hostname or IP address of <span class="codefrag">JobTracker</span>.</td>
  253. <td colspan="1" rowspan="1"><em>host:port</em> pair.</td>
  254. </tr>
  255. <tr>
  256. <td colspan="1" rowspan="1">dfs.name.dir</td>
  257. <td colspan="1" rowspan="1">
  258. Path on the local filesystem where the <span class="codefrag">NameNode</span>
  259. stores the namespace and transactions logs persistently.</td>
  260. <td colspan="1" rowspan="1">
  261. If this is a comma-delimited list of directories then the name
  262. table is replicated in all of the directories, for redundancy.
  263. </td>
  264. </tr>
  265. <tr>
  266. <td colspan="1" rowspan="1">dfs.data.dir</td>
  267. <td colspan="1" rowspan="1">
  268. Comma separated list of paths on the local filesystem of a
  269. <span class="codefrag">DataNode</span> where it should store its blocks.
  270. </td>
  271. <td colspan="1" rowspan="1">
  272. If this is a comma-delimited list of directories, then data will
  273. be stored in all named directories, typically on different
  274. devices.
  275. </td>
  276. </tr>
  277. <tr>
  278. <td colspan="1" rowspan="1">mapred.system.dir</td>
  279. <td colspan="1" rowspan="1">
  280. Path on the HDFS where where the Map-Reduce framework stores
  281. system files e.g. <span class="codefrag">/hadoop/mapred/system/</span>.
  282. </td>
  283. <td colspan="1" rowspan="1">
  284. This is in the default filesystem (HDFS) and must be accessible
  285. from both the server and client machines.
  286. </td>
  287. </tr>
  288. <tr>
  289. <td colspan="1" rowspan="1">mapred.local.dir</td>
  290. <td colspan="1" rowspan="1">
  291. Comma-separated list of paths on the local filesystem where
  292. temporary Map-Reduce data is written.
  293. </td>
  294. <td colspan="1" rowspan="1">Multiple paths help spread disk i/o.</td>
  295. </tr>
  296. <tr>
  297. <td colspan="1" rowspan="1">mapred.tasktracker.tasks.maximum</td>
  298. <td colspan="1" rowspan="1">
  299. The maximum number of map and reduce tasks, which are run
  300. simultaneously on a given <span class="codefrag">TaskTracker</span>, individually.
  301. </td>
  302. <td colspan="1" rowspan="1">
  303. Defaults to 2 (2 maps and 2 reduces), but vary it depending on
  304. your hardware.
  305. </td>
  306. </tr>
  307. <tr>
  308. <td colspan="1" rowspan="1">dfs.hosts/dfs.hosts.exclude</td>
  309. <td colspan="1" rowspan="1">List of permitted/excluded DataNodes.</td>
  310. <td colspan="1" rowspan="1">
  311. If necessary, use these files to control the list of allowable
  312. datanodes.
  313. </td>
  314. </tr>
  315. <tr>
  316. <td colspan="1" rowspan="1">mapred.hosts/mapred.hosts.exclude</td>
  317. <td colspan="1" rowspan="1">List of permitted/excluded TaskTrackers.</td>
  318. <td colspan="1" rowspan="1">
  319. If necessary, use these files to control the list of allowable
  320. tasktrackers.
  321. </td>
  322. </tr>
  323. </table>
  324. <p>Typically all the above parameters are marked as
  325. <a href="api/org/apache/hadoop/conf/Configuration.html#FinalParams">
  326. final</a> to ensure that they cannot be overriden by user-applications.
  327. </p>
  328. <a name="N101BC"></a><a name="Real-World+Cluster+Configurations"></a>
  329. <h5>Real-World Cluster Configurations</h5>
  330. <p>This section lists some non-default configuration parameters which
  331. have been used to run the <em>sort</em> benchmark on very large
  332. clusters.</p>
  333. <ul>
  334. <li>
  335. <p>Some non-default configuration values used to run sort900,
  336. that is 9TB of data sorted on a cluster with 900 nodes:</p>
  337. <table class="ForrestTable" cellspacing="1" cellpadding="4">
  338. <tr>
  339. <th colspan="1" rowspan="1">Parameter</th>
  340. <th colspan="1" rowspan="1">Value</th>
  341. <th colspan="1" rowspan="1">Notes</th>
  342. </tr>
  343. <tr>
  344. <td colspan="1" rowspan="1">dfs.block.size</td>
  345. <td colspan="1" rowspan="1">134217728</td>
  346. <td colspan="1" rowspan="1">HDFS blocksize of 128MB for large file-systems.</td>
  347. </tr>
  348. <tr>
  349. <td colspan="1" rowspan="1">dfs.namenode.handler.count</td>
  350. <td colspan="1" rowspan="1">40</td>
  351. <td colspan="1" rowspan="1">
  352. More NameNode server threads to handle RPCs from large
  353. number of DataNodes.
  354. </td>
  355. </tr>
  356. <tr>
  357. <td colspan="1" rowspan="1">mapred.reduce.parallel.copies</td>
  358. <td colspan="1" rowspan="1">20</td>
  359. <td colspan="1" rowspan="1">
  360. Higher number of parallel copies run by reduces to fetch
  361. outputs from very large number of maps.
  362. </td>
  363. </tr>
  364. <tr>
  365. <td colspan="1" rowspan="1">mapred.child.java.opts</td>
  366. <td colspan="1" rowspan="1">-Xmx512M</td>
  367. <td colspan="1" rowspan="1">
  368. Larger heap-size for child jvms of maps/reduces.
  369. </td>
  370. </tr>
  371. <tr>
  372. <td colspan="1" rowspan="1">fs.inmemory.size.mb</td>
  373. <td colspan="1" rowspan="1">200</td>
  374. <td colspan="1" rowspan="1">
  375. Larger amount of memory allocated for the in-memory
  376. file-system used to merge map-outputs at the reduces.
  377. </td>
  378. </tr>
  379. <tr>
  380. <td colspan="1" rowspan="1">io.sort.factor</td>
  381. <td colspan="1" rowspan="1">100</td>
  382. <td colspan="1" rowspan="1">More streams merged at once while sorting files.</td>
  383. </tr>
  384. <tr>
  385. <td colspan="1" rowspan="1">io.sort.mb</td>
  386. <td colspan="1" rowspan="1">200</td>
  387. <td colspan="1" rowspan="1">Higher memory-limit while sorting data.</td>
  388. </tr>
  389. <tr>
  390. <td colspan="1" rowspan="1">io.file.buffer.size</td>
  391. <td colspan="1" rowspan="1">131072</td>
  392. <td colspan="1" rowspan="1">Size of read/write buffer used in SequenceFiles.</td>
  393. </tr>
  394. </table>
  395. </li>
  396. <li>
  397. <p>Updates to some configuration values to run sort1400 and
  398. sort2000, that is 14TB of data sorted on 1400 nodes and 20TB of
  399. data sorted on 2000 nodes:</p>
  400. <table class="ForrestTable" cellspacing="1" cellpadding="4">
  401. <tr>
  402. <th colspan="1" rowspan="1">Parameter</th>
  403. <th colspan="1" rowspan="1">Value</th>
  404. <th colspan="1" rowspan="1">Notes</th>
  405. </tr>
  406. <tr>
  407. <td colspan="1" rowspan="1">mapred.job.tracker.handler.count</td>
  408. <td colspan="1" rowspan="1">60</td>
  409. <td colspan="1" rowspan="1">
  410. More JobTracker server threads to handle RPCs from large
  411. number of TaskTrackers.
  412. </td>
  413. </tr>
  414. <tr>
  415. <td colspan="1" rowspan="1">mapred.reduce.parallel.copies</td>
  416. <td colspan="1" rowspan="1">50</td>
  417. <td colspan="1" rowspan="1"></td>
  418. </tr>
  419. <tr>
  420. <td colspan="1" rowspan="1">tasktracker.http.threads</td>
  421. <td colspan="1" rowspan="1">50</td>
  422. <td colspan="1" rowspan="1">
  423. More worker threads for the TaskTracker's http server. The
  424. http server is used by reduces to fetch intermediate
  425. map-outputs.
  426. </td>
  427. </tr>
  428. <tr>
  429. <td colspan="1" rowspan="1">mapred.child.java.opts</td>
  430. <td colspan="1" rowspan="1">-Xmx1024M</td>
  431. <td colspan="1" rowspan="1"></td>
  432. </tr>
  433. </table>
  434. </li>
  435. </ul>
  436. <a name="N102D9"></a><a name="Slaves"></a>
  437. <h4>Slaves</h4>
  438. <p>Typically you choose one machine in the cluster to act as the
  439. <span class="codefrag">NameNode</span> and one machine as to act as the
  440. <span class="codefrag">JobTracker</span>, exclusively. The rest of the machines act as
  441. both a <span class="codefrag">DataNode</span> and <span class="codefrag">TaskTracker</span> and are
  442. referred to as <em>slaves</em>.</p>
  443. <p>List all slave hostnames or IP addresses in your
  444. <span class="codefrag">conf/slaves</span> file, one per line.</p>
  445. <a name="N102F8"></a><a name="Logging"></a>
  446. <h4>Logging</h4>
  447. <p>Hadoop uses the <a href="http://logging.apache.org/log4j/">Apache
  448. log4j</a> via the <a href="http://commons.apache.org/logging/">Apache
  449. Commons Logging</a> framework for logging. Edit the
  450. <span class="codefrag">conf/log4j.properties</span> file to customize the Hadoop
  451. daemons' logging configuration (log-formats and so on).</p>
  452. <p>Once all the necessary configuration is complete, distribute the files
  453. to the <span class="codefrag">HADOOP_CONF_DIR</span> directory on all the machines,
  454. typically <span class="codefrag">${HADOOP_HOME}/conf</span>.</p>
  455. </div>
  456. <a name="N10318"></a><a name="Hadoop+Startup"></a>
  457. <h2 class="h3">Hadoop Startup</h2>
  458. <div class="section">
  459. <p>To start a Hadoop cluster you will need to start both the HDFS and
  460. Map-Reduce cluster.</p>
  461. <p>
  462. Format a new distributed filesystem:<br>
  463. <span class="codefrag">$ bin/hadoop namenode -format</span>
  464. </p>
  465. <p>
  466. Start the HDFS with the following command, run on the designated
  467. <span class="codefrag">NameNode</span>:<br>
  468. <span class="codefrag">$ bin/start-dfs.sh</span>
  469. </p>
  470. <p>The <span class="codefrag">bin/start-dfs.sh</span> script also consults the
  471. <span class="codefrag">${HADOOP_CONF_DIR}/slaves</span> file on the <span class="codefrag">NameNode</span>
  472. and starts the <span class="codefrag">DataNode</span> daemon on all the listed slaves.</p>
  473. <p>
  474. Start Map-Reduce with the following command, run on the designated
  475. <span class="codefrag">JobTracker</span>:<br>
  476. <span class="codefrag">$ bin/start-mapred.sh</span>
  477. </p>
  478. <p>The <span class="codefrag">bin/start-mapred.sh</span> script also consults the
  479. <span class="codefrag">${HADOOP_CONF_DIR}/slaves</span> file on the <span class="codefrag">JobTracker</span>
  480. and starts the <span class="codefrag">TaskTracker</span> daemon on all the listed slaves.
  481. </p>
  482. </div>
  483. <a name="N1035E"></a><a name="Hadoop+Shutdown"></a>
  484. <h2 class="h3">Hadoop Shutdown</h2>
  485. <div class="section">
  486. <p>
  487. Stop HDFS with the following command, run on the designated
  488. <span class="codefrag">NameNode</span>:<br>
  489. <span class="codefrag">$ bin/stop-dfs.sh</span>
  490. </p>
  491. <p>The <span class="codefrag">bin/stop-dfs.sh</span> script also consults the
  492. <span class="codefrag">${HADOOP_CONF_DIR}/slaves</span> file on the <span class="codefrag">NameNode</span>
  493. and stops the <span class="codefrag">DataNode</span> daemon on all the listed slaves.</p>
  494. <p>
  495. Stop Map-Reduce with the following command, run on the designated
  496. the designated <span class="codefrag">JobTracker</span>:<br>
  497. <span class="codefrag">$ bin/stop-mapred.sh</span>
  498. <br>
  499. </p>
  500. <p>The <span class="codefrag">bin/stop-mapred.sh</span> script also consults the
  501. <span class="codefrag">${HADOOP_CONF_DIR}/slaves</span> file on the <span class="codefrag">JobTracker</span>
  502. and stops the <span class="codefrag">TaskTracker</span> daemon on all the listed slaves.</p>
  503. </div>
  504. </div>
  505. <div class="clearboth">&nbsp;</div>
  506. </div>
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  515. 2007 <a href="http://www.apache.org/licenses/">The Apache Software Foundation.</a>
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