memcached

一时失言乱红尘 2022-08-06 17:04 188阅读 0赞

memcached是高性能的分布式内存缓存数据库。 一般的使用目的是，通过缓存数据库查询结果，减少数据库访问次数，以提高动态Web应用的速度、 提高可扩展性。

![2008092816494460.png][]

memcached的特点

一、memcached的服务器客户端通信使用简单的基于文本行的协议。因此，通过telnet 也能在memcached上保存数据、取得数据。

$ telnet localhost 11211

二、基于libevent的事件处理

三、内容容量达到指定值之后，就基于LRU(Least Recently Used)算法自动删除不使用的缓存。

四、 各个memcached不会互相通信以共享信息。分布式算法完全由客户端实现。

memcached的使用

默认情况下memcached安装到/usr/local/bin下。

启动命令

保存数据命令与方法

向memcached保存数据时可以指定期限(秒)。不指定期限时，memcached按照LRU算法保存数据。

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   <td style="margin:0px; padding:5px; line-height:21.6000003814697px; border:1px solid rgb(192,192,192); border-collapse:collapse"> 选项</td> 
   <td style="margin:0px; padding:5px; line-height:21.6000003814697px; border:1px solid rgb(192,192,192); border-collapse:collapse"> 说明</td> 
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   <td style="margin:0px; padding:5px; line-height:21.6000003814697px; border:1px solid rgb(192,192,192); border-collapse:collapse"> add</td> 
   <td style="margin:0px; padding:5px; line-height:21.6000003814697px; border:1px solid rgb(192,192,192); border-collapse:collapse"> 仅当存储空间中不存在键相同的数据时才保存</td> 
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   <td style="margin:0px; padding:5px; line-height:21.6000003814697px; border:1px solid rgb(192,192,192); border-collapse:collapse"> replace</td> 
   <td style="margin:0px; padding:5px; line-height:21.6000003814697px; border:1px solid rgb(192,192,192); border-collapse:collapse"> 仅当存储空间中存在键相同的数据时才保存</td> 
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   <td style="margin:0px; padding:5px; line-height:21.6000003814697px; border:1px solid rgb(192,192,192); border-collapse:collapse"> set</td> 
   <td style="margin:0px; padding:5px; line-height:21.6000003814697px; border:1px solid rgb(192,192,192); border-collapse:collapse"> 与add和replace不同，无论何时都保存</td> 
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数据操作

command <key> <flags> <expiration time> <bytes>
    <value>

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   <th style="margin:0px; padding:10px 5px 10px 3px; outline:0px; font-size:undefined; vertical-align:top; border-width:1px 0px 0px; border-style:solid none none; border-top-color:rgb(221,221,221)"> 参数</th> 
   <th style="margin:0px; padding:10px 5px 10px 3px; outline:0px; font-size:undefined; vertical-align:top; border-width:1px 0px 0px; border-style:solid none none; border-top-color:rgb(221,221,221)"> 用法</th> 
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   <td style="margin:0px; padding:8px 10px 5px 3px; outline:0px; font-size:undefined; vertical-align:top; border-left-width:0px; border-left-style:none; border-top-width:2px; border-top-style:solid; border-top-color:rgb(153,153,153); color:rgb(85,85,85); border-right-width:0px; border-right-style:none"> key</td> 
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   <td style="margin:0px; padding:8px 10px 5px 3px; outline:0px; font-size:undefined; vertical-align:top; border-left-width:0px; border-left-style:none; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221); color:rgb(85,85,85); border-right-width:0px; border-right-style:none; background:rgb(215,237,248)"> flags</td> 
   <td style="margin:0px; padding:8px 5px 5px 3px; outline:0px; font-size:undefined; vertical-align:top; border-left-width:3px; border-left-style:solid; border-left-color:rgb(255,255,255); border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221); color:rgb(85,85,85); border-right-width:0px; border-right-style:none; background:rgb(215,237,248)"> 可以包括键值对的整型参数，客户机使用它存储关于键值对的额外信息</td> 
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  <tr style="margin:0px; padding:0px; outline:0px; font-size:undefined; vertical-align:baseline"> 
   <td style="margin:0px; padding:8px 10px 5px 3px; outline:0px; font-size:undefined; vertical-align:top; border-left-width:0px; border-left-style:none; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221); color:rgb(85,85,85); border-right-width:0px; border-right-style:none"> expiration time</td> 
   <td style="margin:0px; padding:8px 5px 5px 3px; outline:0px; font-size:undefined; vertical-align:top; border-left-width:3px; border-left-style:solid; border-left-color:rgb(255,255,255); border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221); color:rgb(85,85,85); border-right-width:0px; border-right-style:none"> 在缓存中保存键值对的时间长度（以秒为单位，0 表示永远）</td> 
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   <td style="margin:0px; padding:8px 10px 5px 3px; outline:0px; font-size:undefined; vertical-align:top; border-left-width:0px; border-left-style:none; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221); color:rgb(85,85,85); border-right-width:0px; border-right-style:none"> bytes</td> 
   <td style="margin:0px; padding:8px 5px 5px 3px; outline:0px; font-size:undefined; vertical-align:top; border-left-width:3px; border-left-style:solid; border-left-color:rgb(255,255,255); border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221); color:rgb(85,85,85); border-right-width:0px; border-right-style:none"> 在缓存中存储的字节点</td> 
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   <td style="margin:0px; padding:8px 10px 5px 3px; outline:0px; font-size:undefined; vertical-align:top; border-left-width:0px; border-left-style:none; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221); color:rgb(85,85,85); border-right-width:0px; border-right-style:none"> value</td> 
   <td style="margin:0px; padding:8px 5px 5px 3px; outline:0px; font-size:undefined; vertical-align:top; border-left-width:3px; border-left-style:solid; border-left-color:rgb(255,255,255); border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221); color:rgb(85,85,85); border-right-width:0px; border-right-style:none"> 存储的值（始终位于第二行）</td> 
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1.获取数据可以使用get和get\_multi方法。

2.删除数据使用delete方法。

数值加减

incr  <key> <num>

decr <key> <num>

增添内容

在数据末尾添加内容

append  <key> <flags> <expiration time> <bytes>

<value>

在数据开头添加内容

prepend

### 缓存管理命令 ###