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ES7.8.1 集群搭建踩坑记录
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<p>时隔两年多时间，再次接触 elasticsearch,准备在测试环境搭建一套 ES 集群用来测试</p>
<p>之前使用ES还是在其1.4.x~2.0.x左右的时候，现在 ES 版本已经发展到了7.x以上了(中间经历过于kibana同步版本号,所以版本变动比较大)</p>
<h2 id="单机安装"><a href="#单机安装" class="headerlink" title="单机安装"></a>单机安装</h2><p>大致安装步骤和之前的版本差别不大,依然保持了其开箱即用的特性,只需要很少的配置即可</p>
<p>单机很简单，修改集群名称，节点名称,数据及日志目录,以及监听绑定的ip,然后直接运行可执行文件即可</p>
<figure class="highlight routeros"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line">注：下载的打包文件中，附带一个openjdk可以直接使用，如果使用 supervisor 来管理 es, 可以使用</span><br><span class="line">supervisor 的 environment 功能，来设置 JAVA_HOME 环境变量</span><br><span class="line"></span><br><span class="line">配置如下，ES_HOME 即 elasticsearch 解压后文件夹所在目录</span><br><span class="line"></span><br><span class="line">[es]</span><br><span class="line"><span class="attribute">command</span>=<span class="variable">$ES_HOME</span>/bin/elasticsearch</span><br><span class="line"><span class="attribute">directory</span>=<span class="variable">$ES_HOME</span></span><br><span class="line"><span class="attribute">environment</span>=JAVA_HOME=$ES_HOME/jdk</span><br></pre></td></tr></table></figure>
<p>单机没什么问题，很顺畅的就启动起来了，通过 curl <a href="http://ip:es_port" target="_blank" rel="noopener">http://ip:es_port</a> 可以得到很熟悉的返回：<br><figure class="highlight json"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line">{</span><br><span class="line"> <span class="attr">"name"</span> : <span class="string">"node1"</span>,</span><br><span class="line"> <span class="attr">"cluster_name"</span> : <span class="string">"cluster-name"</span>,</span><br><span class="line"> <span class="attr">"cluster_uuid"</span> : <span class="string">"2c2jICSxTHK_jUcJjaBucw"</span>,</span><br><span class="line"> <span class="attr">"version"</span> : {</span><br><span class="line"> <span class="attr">"number"</span> : <span class="string">"7.8.1"</span>,</span><br><span class="line"> <span class="attr">"build_flavor"</span> : <span class="string">"default"</span>,</span><br><span class="line"> <span class="attr">"build_type"</span> : <span class="string">"tar"</span>,</span><br><span class="line"> <span class="attr">"build_hash"</span> : <span class="string">"b5ca9c58fb664ca8bf9e4057fc229b3396bf3a89"</span>,</span><br><span class="line"> <span class="attr">"build_date"</span> : <span class="string">"2020-07-21T16:40:44.668009Z"</span>,</span><br><span class="line"> <span class="attr">"build_snapshot"</span> : <span class="literal">false</span>,</span><br><span class="line"> <span class="attr">"lucene_version"</span> : <span class="string">"8.5.1"</span>,</span><br><span class="line"> <span class="attr">"minimum_wire_compatibility_version"</span> : <span class="string">"6.8.0"</span>,</span><br><span class="line"> <span class="attr">"minimum_index_compatibility_version"</span> : <span class="string">"6.0.0-beta1"</span></span><br><span class="line"> },</span><br><span class="line"> <span class="attr">"tagline"</span> : <span class="string">"You Know, for Search"</span></span><br><span class="line">}</span><br></pre></td></tr></table></figure></p>
<h2 id="组建集群"><a href="#组建集群" class="headerlink" title="组建集群"></a>组建集群</h2><p>既然单机的起来的，那如法炮制，将配置文件复制一份，修改了其 node name, scp到另外一台机器上，准备好 supervisor 配置，准备开始组建两个节点组成的集群</p>
<p>满以为不会有什么问题，启动之后，发现，第二个节点，怎么也加入不到第一个节点之中<br>
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<h2 id="初始"><a href="#初始" class="headerlink" title="初始"></a>初始</h2><p><code>git</code> 项目中，可以使用以下命令为项目添加<code>submodule</code></p>
<figure class="highlight stylus"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git submodule add -<span class="selector-tag">b</span> branch_name git@github<span class="selector-class">.com</span>:javasgl/xxx<span class="selector-class">.git</span> module_path</span><br></pre></td></tr></table></figure>
<p>执行以上命令后，会在当前项目下生成一个<code>.gitmodules</code> 文件，内容如下</p>
<figure class="highlight stylus"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">[submodule <span class="string">"module_path"</span>]</span><br><span class="line"> path = module_path</span><br><span class="line"> url = git@github<span class="selector-class">.com</span>:javasgl/xxx.git</span><br><span class="line"> branch = branch_name</span><br></pre></td></tr></table></figure>
<p>同时也将修改 <code>.git/config</code>文件<br><figure class="highlight stylus"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">[submodule <span class="string">"module_path"</span>]</span><br><span class="line"> url = git@github<span class="selector-class">.com</span>:javasgl/xxx.git</span><br><span class="line"> active = true</span><br></pre></td></tr></table></figure></p>
<p>此时，执行以下命令即可从远程拉取相关代码到<code>submodule</code>中:<br><figure class="highlight armasm"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="symbol">git</span> <span class="keyword">submodule </span>update --init</span><br><span class="line"></span><br><span class="line">// 可以使用 git <span class="keyword">submodule </span>deinit 重新初始化</span><br></pre></td></tr></table></figure></p>
<p>执行之后，会在 <code>.git/modules/module_path/</code> 下看到 <code>submodeule</code>相关的代码</p>
<figure class="highlight asciidoc"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="title">.git/modules</span></span><br><span class="line">└── module<span class="emphasis">_path</span></span><br></pre></td></tr></table></figure>
<h2 id="变更"><a href="#变更" class="headerlink" title="变更"></a>变更</h2><p>有时候，对于已经添加了submodule的项目，如果想更换 <code>submodule</code> 的地址，那个这就比较麻烦，目前<code>git</code>并没有直接提供相关命令,需要进行一系列的手工操作</p>
<p>简单记录如下，备查</p>
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<p>缓存使用过过程中常见问题基本是以下几个问题：</p>
<ul>
<li>缓存穿透问题 </li>
<li>缓存并发问题 </li>
<li>热点数据问题</li>
<li>数据一致问题</li>
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<p>这些问题不是独立的，一般都会存在因果关系或者同时存在</p>
<p>下面列举一下问题原因及基本解决思路</p>
<h2 id="缓存穿透-过期"><a href="#缓存穿透-过期" class="headerlink" title="缓存穿透/过期"></a>缓存穿透/过期</h2><p>缓存穿透问题是指请求数据在缓存中没有找到，导致请求直接打到数据库的情况</p>
<p>这种场景下，大致有两类原因可以导致这类问题：<br>
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<p>mysql 5.7 以后带来了一个新的功能，即 “Generated Columns”,字面意思可翻译为 “生成列”，顾名思义，这列的数据不能被直接插入或者更新，而是依据一定的规则自动生成。</p>
<p>Generated Columns 定义方式如下:<br><figure class="highlight prolog"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">col_name data_type [<span class="symbol">GENERATED</span> <span class="symbol">ALWAYS</span>] <span class="symbol">AS</span> (expr)</span><br><span class="line"> [<span class="symbol">VIRTUAL</span> | <span class="symbol">STORED</span>] [<span class="symbol">NOT</span> <span class="symbol">NULL</span> | <span class="symbol">NULL</span>]</span><br><span class="line"> [<span class="symbol">UNIQUE</span> [<span class="symbol">KEY</span>]] [[<span class="symbol">PRIMARY</span>] <span class="symbol">KEY</span>]</span><br><span class="line"> [<span class="symbol">COMMENT</span> <span class="string">'string'</span>]</span><br></pre></td></tr></table></figure></p>
<p>注：</p>
<blockquote>
<p>默认是 VIRTUAL,即 虚拟列，不实际占用存储空间，在读取数据时即时计算而来；<br>STORED 则与之相反，它会生成真实的数据列，和正常的列无异，占用存储空间;<br>两者在限制上各有细微区别，具体可查看文末 mysql/mariadb 链接阅读详情</p>
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<p>以下样例,展示了自动生成指定时间字段的月份:<br>
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