memcached的安装以及SpyMemcached的使用

1、Memcached的安装

• memcached依赖于libevent库，所以先安装libevenet库。

tar -xzf libevent-1.4.14b-stable.tar.gz

cd libevent-1.4.14b-stable

./configure

make

sudo make install

• memcached的下载地址，安装步骤和libevenet一样。
• 安装完memcached以后，执行memcached -h打印帮助信息
  

2、Memcached的JAVA调用

• 建议先到网上找一个介绍Memcached的文档看一下：memcached全面剖析.pdf
  

• memcached客户端使用google的spymemcached，可以直接下载，如果使用maven的话，GAV坐标如下：

    <dependency>
        <groupId>com.google.code.simple-spring-memcached</groupId>
        <artifactId>spymemcached</artifactId>
        <version>2.8.4</version>
    </dependency>

• spymemcached的基本使用很简单：new一个MemcachedClient实例，然后调用set/add/replace/get命令即可，注意用完后要关闭客户端：调用shutdown()：

MemcachedClient mc = new MemcachedClient(new InetSocketAddress(CONSTANT.MEMCACHED_ADDR, CONSTANT.MEMCACHED_PORT));

mc.set(“key”, 0, "value");

mc.shutdown();

• pymemcached的高级用法如下：

在创建MemcachedClient的时候指定Memcached地址列表，支持Memcached集群使用；

使用异步查询asyncGet，防止因为查询不到值导致的客户端挂死问题

      // Get a memcached client connected to several servers
      // over the binary protocol
      MemcachedClient c = new MemcachedClient(new BinaryConnectionFactory(),
              AddrUtil.getAddresses("server1:11211 server2:11211"));

      // Try to get a value, for up to 5 seconds, and cancel if it
      // doesn't return
      Object myObj = null;
      Future<Object> f = c.asyncGet("someKey");
      try {
          myObj = f.get(5, TimeUnit.SECONDS);
      // throws expecting InterruptedException, ExecutionException
      // or TimeoutException
      } catch (Exception e) {  /*  /
          // Since we don't need this, go ahead and cancel the operation.
          // This is not strictly necessary, but it'll save some work on
          // the server.  It is okay to cancel it if running.
          f.cancel(true);
          // Do other timeout related stuff
      }

• 使用二进制协议如下，需要在创建MemcachedClient的时候，指定二进制链接工厂：BinaryConnectionFactory

// Get a memcached client connected to several servers with the binary protocol
MemcachedClient c=new MemcachedClient(
        new BinaryConnectionFactory(),
        AddrUtil.getAddresses("server1:11212 server2:11212"));

// Proceed to do cool stuff with memcached using the binary protocol.

• spymemcached的jar包、源码、api文档可以到google code上下载

• memcached的key有如下限制，可参考这篇文章：
  

key最大250个字节、key中不能有控制字符和空格、item最大1M字节、item的过期时间最大30天