搭建高可用mongodb集群（一）——配置mongodb
<p>在大数据的时代，传统的关系型数据库要能更高的服务必须要解决高并发读写、海量数据高效存储、高可扩展性和高可用性这些难题。不过就是因为这些问题Nosql诞生了。</p><p>NOSQL有这些优势：</p>
<p><strong>大数据量</strong>，可以通过廉价服务器存储大量的数据，轻松摆脱传统mysql单表存储量级限制。</p>
<p><strong>高扩展性</strong>，Nosql去掉了关系数据库的关系型特性，很容易横向扩展，摆脱了以往老是纵向扩展的诟病。</p>
<p><strong>高性能</strong>，Nosql通过简单的key-value方式获取数据，非常快速。还有NoSQL的Cache是记录级的，是一种细粒度的Cache，所以NoSQL在这个层面上来说就要性能高很多。</p>
<p><strong>灵活的数据模型</strong>，NoSQL无需事先为要存储的数据建立字段，随时可以存储自定义的数据格式。而在关系数据库里，增删字段是一件非常麻烦的事情。如果是非常大数据量的表，增加字段简直就是一个噩梦。</p>
<p><strong>高可用</strong>，NoSQL在不太影响性能的情况，就可以方便的实现高可用的架构。比如mongodb通过mongos、mongo分片就可以快速配置出高可用配置。</p>
<p>在nosql数据库里，大部分的查询都是键值对（key、value）的方式。MongoDB是一个介于关系数据库和非关系数据库之间的产品，是非关系数据库当中最像关系数据库的。支持类似于面向对象的查询语言，几乎可以实现类似关系数据库单表查询的绝大部分功能，而且还支持对数据建立索引。所以这个非常方便，我们可以用sql操作MongoDB，从关系型数据库迁移过来，开发人员学习成本会大大减少。如果再对底层的sql API做一层封装，开发基本可以感觉不到mongodb和关系型数据库的区别。同样MongoDB也是号称自己能够快速搭建一个高可用可扩展的的分布式集群，网上有很多搭建的文章，在我们搭建的时候还需要查找修改很多东西，所以把自己实战的步骤记录下来以备忘。我们看看如何一步一步搭建这个东东。</p>
<p><strong>一、mongodb单实例</strong>。这种配置只适合简易开发时使用，生产使用不行，因为单节点挂掉整个数据业务全挂，如下图。</p>
<p><img class="alignleft size-full wp-image-593 lazyload" alt="mongodb1" width="259" height="124" data-src="http://www.lanceyan.com/wp-content/uploads/2013/11/mongodb1.png"></p>
<p>虽然不能生产使用，但这个模式可以快速搭建启动，并且能够用mongodb的命令操作数据库。下面列出在linux下安装单节点mongodb的步骤</p>
<p>1、建立mongodb测试文件夹</p>
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<div class="bash codecolorer"><span class="co0">#存放整个mongodb文件</span><br><span class="kw2">mkdir</span> <span class="re5">-p</span> <span class="sy0">/</span>data<span class="sy0">/</span>mongodbtest<span class="sy0">/</span>single <br><br><span class="co0">#存放mongodb数据文件</span><br><span class="kw2">mkdir</span> <span class="re5">-p</span> <span class="sy0">/</span>data<span class="sy0">/</span>mongodbtest<span class="sy0">/</span>single<span class="sy0">/</span>data<br><br><span class="co0">#进入mongodb文件夹</span><br><span class="kw3">cd</span> <span class="sy0">/</span>data<span class="sy0">/</span>mongodbtest<span class="sy0">/</span>single</div>
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<p>2、下载mongodb的安装程序包</p>
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<div class="bash codecolorer"><span class="kw2">wget</span> http:<span class="sy0">//</span>fastdl.mongodb.org<span class="sy0">/</span>linux<span class="sy0">/</span>mongodb-linux-x86_64-2.4.6.tgz<br><br><span class="co0">#解压下载的压缩包 </span><br><span class="kw2">tar</span> xvzf mongodb-linux-x86_64-2.4.6.tgz<br><br><span class="co0">#进入mongodb程序执行文件夹</span><br><span class="kw3">cd</span> mongodb-linux-x86_64-2.4.6<span class="sy0">/</span>bin<span class="sy0">/</span></div>
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<p>3、启动单实例mongodb</p>
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<div class="bash codecolorer">mongod <span class="re5">--dbpath</span> <span class="sy0">/</span>data<span class="sy0">/</span>mongodbtest<span class="sy0">/</span>single<span class="sy0">/</span>data</div>
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<p>输出日志如下，成功！</p>
<p> db version v2.4.6<br>……..<br> waiting for connections on port <strong>27017</strong><br> admin web console waiting for connections on port 28017</p>
<p>mongodb默认自带提供了web访问接口，通过 IP + 端口的形式可以访问。</p>
<p>http://192.168.0.1:28017/</p>
<p><img class="alignleft size-full wp-image-594 lazyload" alt="mongodb2" width="508" height="341" data-src="http://www.lanceyan.com/wp-content/uploads/2013/11/mongodb2.png"></p>
<p><strong>二、主从模式</strong>。使用mysql数据库时大家广泛用到，采用双机备份后主节点挂掉了后从节点可以接替主机继续服务。所以这种模式比单节点的高可用性要好很多。</p>
<p><img class="alignleft size-full wp-image-595 lazyload" alt="mongodb3" width="281" height="304" data-src="http://www.lanceyan.com/wp-content/uploads/2013/11/mongodb3.png"></p>
<p>下面看一下怎么一步步搭建一个mongodb的主从复制节点：</p>
<ul>
<li>1、准备两台机器 192.168.0.1 和 192.168.0.2。 192.168.0.1 当作<strong>主节点</strong>， 192.168.0.2作为<strong>从节点</strong>。</li>
<li>2、分别下载mongodb安装程序包。在192.168.0.1上建立文件夹 /data/mongodbtest/<strong>master</strong>，192.168.0.2建立文件夹/data/mongodbtest/<strong>slave</strong>。</li>
<li>3、在192.168.0.1启动mongodb主节点程序。注意后面的这个 “ <strong>–master </strong>”参数，标示主节点。
<p>mongod –dbpath /data/mongodbtest/master –master</p>
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<p>输出日志如下，成功！</p>
<p> MongoDB starting : pid=18285 port=27017 dbpath=/data/mongodbtest/master master=1<br>#日志显示主节点参数<br> options: { dbpath: “/data/mongodbtest/master”, <strong>master: true</strong> }<br>……..<br> waiting for connections on port 27017</p>
<p>4、在192.168.0.2启动mongodb从节点程序。关键配置，指定主节点ip地址和端口 –source 192.168.0.1:27017 和 标示从节点 –source 参数。</p>
<p>mongod –dbpath /data/mongodbtest/slave <strong>–slave –source</strong> 192.168.0.1:27017</p>
<p>输出日志如下，成功！</p>
<p> MongoDB starting : pid=17888 port=27017 dbpath=/data/mongodbtest/slave slave=1<br>……..<br>#日志显示从节点参数<br> options: { dbpath: “/data/mongodbtest/slave”, <strong>slave: true, source</strong>: “192.168.0.1:27017″ }<br>……..<br> waiting for connections on port 27017<br>#日志显示从节点 从主节点同步复制数据<br> repl: from host:192.168.0.1:27017</p>
<p>5、测试主从复制。</p>
<p>在主节点上连接到终端：</p>
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<div class="bash codecolorer">mongo 127.0.0.1<br><br><span class="co0">#建立test 数据库。</span><br>use <span class="kw3">test</span>;<br><br>往testdb表插入数据。<br><span class="sy0">></span> db.testdb.insert<span class="br0">(</span><span class="br0">{</span><span class="st0">"test1"</span>:<span class="st0">"testval1"</span><span class="br0">}</span><span class="br0">)</span><br><br>查询testdb数据看看是否成功。<br><span class="sy0">></span> db.testdb.find<span class="br0">(</span><span class="br0">)</span>;<br><span class="br0">{</span> <span class="st0">"_id"</span> : ObjectId<span class="br0">(</span><span class="st0">"5284e5cb1f4eb215b2ecc463"</span><span class="br0">)</span>, <span class="st0">"test1"</span> : <span class="st0">"testval1"</span> <span class="br0">}</span></div>
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<p>可以看到主机的同步日志</p>
<p> connection accepted from 192.168.0.2:37285 #3 (2 connections now open)<br> update local.slaves query: { _id: ObjectId(’5284e6268ed115d6238bdb39′), config: { host: “192.168.0.2:35271″, upgradeNeeded: true }, ns: “local.oplog.$main” } update: { $set: { syncedTo: Timestamp 1384441570000|1 } } nscanned:1 nupdated:1 fastmod:1 keyUpdates:0 locks(micros) w:132015 132ms</p>
<p>检查从主机的数据。</p>
<p>mongo 127.0.0.1</p>
<p>查看当前数据库。</p>
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<div class="bash codecolorer"><span class="sy0">></span> show dbs;<br> <span class="kw3">local</span> 0.203125GB<br> <span class="kw3">test</span> 0.203125GB<br><br>use <span class="kw3">test</span>;<br>db.testdb.find<span class="br0">(</span><span class="br0">)</span>;<br><span class="br0">{</span> <span class="st0">"_id"</span> : ObjectId<span class="br0">(</span><span class="st0">"5284e5cb1f4eb215b2ecc463"</span><span class="br0">)</span>, <span class="st0">"test1"</span> : <span class="st0">"testval1"</span> <span class="br0">}</span></div>
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<p>查询后数据已经同步过来了。再看看日志，发现从主机确实从主机同步了数据。</p>
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<div class="bash codecolorer">Thu Nov <span class="nu0">14</span> <span class="nu0">23</span>:05:<span class="nu0">13</span> <span class="br0">[</span>replslave<span class="br0">]</span> repl: checkpoint applied <span class="nu0">15</span> operations<br>Thu Nov <span class="nu0">14</span> <span class="nu0">23</span>:05:<span class="nu0">13</span> <span class="br0">[</span>replslave<span class="br0">]</span> repl: syncedTo: Nov <span class="nu0">14</span> <span class="nu0">23</span>:08:<span class="nu0">10</span> 5284e75a:<span class="nu0">1</span></div>
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<p>查看服务状态</p>
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<div class="bash codecolorer"><span class="sy0">></span> db.printReplicationInfo<span class="br0">(</span><span class="br0">)</span>;<br> this is a slave, printing slave replication info.<br> source: 192.168.0.1:<span class="nu0">27017</span><br> syncedTo: Sun Nov <span class="nu0">17</span> <span class="nu0">2013</span> <span class="nu0">16</span>:04:02 GMT+0800 <span class="br0">(</span>CST<span class="br0">)</span><br> = <span class="re5">-54</span> secs ago <span class="br0">(</span>-0.01hrs<span class="br0">)</span></div>
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<p>到此主从结构的mongodb搭建好了。</p>
<p><strong>故障转移测试</strong>，现在两台服务器如果主服务器挂掉了，从服务器可以正常运转吗？</p>
<p>a、先测试下从服务器可以当成主服务器吗，也就是往从服务器里写能够同步主服务器吗？</p>
<p> </p>
<p>在192.168.0.2上连接mongodb。</p>
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<div class="bash codecolorer">mongo 127.0.0.1:<span class="nu0">27017</span><br><span class="sy0">></span> db.testdb.insert<span class="br0">(</span><span class="br0">{</span><span class="st0">"test3"</span>:<span class="st0">"testval3"</span><span class="br0">}</span><span class="br0">)</span>;<br>not master</div>
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<p>可以看到 mongodb的从节点是不能提供写操作的，只能提供读操作。</p>
<p>b、如果从服务器挂掉，主服务器还可以提供服务。如果主服务器挂掉了从服务器能否自动变为可写。<br>测试一下！</p>
<p>先杀掉原来的mongodb主服务器。</p>
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<div class="bash codecolorer"><span class="kw2">kill</span> <span class="re5">-3</span> <span class="sy0">`</span><span class="kw2">ps</span> <span class="re5">-ef</span><span class="sy0">|</span><span class="kw2">grep</span> mongod<span class="sy0">|</span><span class="kw2">grep</span> <span class="re5">-v</span> <span class="kw2">grep</span><span class="sy0">|</span><span class="kw2">awk</span> <span class="st_h">'{print $2}'</span><span class="sy0">`</span></div>
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<p>测试从服务器能否可写。在192.168.0.2上连接mongodb测试。</p>
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<div class="bash codecolorer"><span class="sy0">></span> db.testdb.insert<span class="br0">(</span><span class="br0">{</span><span class="st0">"test3"</span>:<span class="st0">"testval3"</span><span class="br0">}</span><span class="br0">)</span>;<br>not master</div>
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<p>看起来从服务器没有自动接替主服务器的功能，只有手工处理了！</p>
<p>停止从服务器，在原数据文件启动并添加主服务器标示。</p>
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<div class="bash codecolorer">mongod <span class="re5">--dbpath</span> <span class="sy0">/</span>data<span class="sy0">/</span>mongodbtest<span class="sy0">/</span>slave <span class="re5">--master</span></div>
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<p>等到启动成功（时间有点长）。在192.168.0.2 上 连接</p>
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<div class="bash codecolorer">mongo 192.168.0.2:<span class="nu0">27017</span></div>
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<p>。</p>
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<div class="bash codecolorer"><span class="sy0">></span> db.testdb.find<span class="br0">(</span><span class="br0">)</span>;<br><span class="br0">{</span> <span class="st0">"_id"</span> : ObjectId<span class="br0">(</span><span class="st0">"5288629e9b0318be4b20bd4c"</span><span class="br0">)</span>, <span class="st0">"test1"</span> : <span class="st0">"testval1"</span> <span class="br0">}</span><br><span class="br0">{</span> <span class="st0">"_id"</span> : ObjectId<span class="br0">(</span><span class="st0">"528862d69b0318be4b20bd4d"</span><span class="br0">)</span>, <span class="st0">"test2"</span> : <span class="st0">"testval2"</span> <span class="br0">}</span></div>
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<p>成功！</p>
<p><strong>多个从节点</strong>。现在只是一个数据库服务器又提供写又提供读，机器承载会出现瓶颈。大家还记得mysql里的读写分离吗？把20%的写放到主节点，80%的读放到从节点分摊了减少了服务器的负载。但是大部分应用都是读操作带来的压力，一个从节点压力负载不了，可以把一个从节点变成多个节点。那mongodb的一主多从可以支持吗？答案是肯定的。</p>
<p><img class="alignleft size-full wp-image-596 lazyload" alt="mongodb4" width="323" height="335" data-src="http://www.lanceyan.com/wp-content/uploads/2013/11/mongodb4.png"></p>
<p>为了方便测试，在192.168.0.2上再建立一个文件夹 /data/mongodbtest/slave2 作为另一个slave服务器。<br>启动slave2服务，</p>
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<div class="bash codecolorer">mongod <span class="re5">--dbpath</span> <span class="sy0">/</span>data<span class="sy0">/</span>mongodbtest<span class="sy0">/</span>slave1 <span class="re5">--slave</span> <span class="re5">--port</span> <span class="nu0">27017</span> <span class="re5">--source</span> 192.168.0.1:<span class="nu0">27017</span>。</div>
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<p>成功启动后通过mongodb连接测试：</p>
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<div class="bash codecolorer"><span class="sy0">></span> db.testdb.find<span class="br0">(</span><span class="br0">)</span>;<br><span class="br0">{</span> <span class="st0">"_id"</span> : ObjectId<span class="br0">(</span><span class="st0">"5288629e9b0318be4b20bd4c"</span><span class="br0">)</span>, <span class="st0">"test1"</span> : <span class="st0">"testval1"</span> <span class="br0">}</span><br><span class="br0">{</span> <span class="st0">"_id"</span> : ObjectId<span class="br0">(</span><span class="st0">"528862d69b0318be4b20bd4d"</span><span class="br0">)</span>, <span class="st0">"test2"</span> : <span class="st0">"testval2"</span> <span class="br0">}</span></div>
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<p>搭建了这套主从复制系统是不是就很稳健了，其实不然。。。看看这几个问题？</p>
<ul>
<li>主节点挂了能否自动切换连接？目前需要手工切换。</li>
<li>主节点的写压力过大如何解决？</li>
<li>从节点每个上面的数据都是对数据库全量拷贝，从节点压力会不会过大？</li>
<li>就算对从节点路由实施路由访问策略能否做到自动扩展？</li>
</ul>
<p>还有这么多问题，有其他解决方案吗？下一篇接着弄。</p>
<p>参考：<br>NoSQL开篇——为什么要使用NoSQL http://www.infoq.com/cn/news/2011/01/nosql-why/<br>mongodb手册 http://cn.docs.mongodb.org/manual/single/</p>
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<p><strong>原创文章，转载请注明：</strong> 转载自LANCEYAN.COM</p>
<p><strong>本文链接地址:</strong> 搭建高可用mongodb集群（一）——配置mongodb</p>
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来源：https://www.cnblogs.com/lanceyan/p/3428741.html
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