Memcached的使用
一 、 安装Memcached及Memcached配置和状态查询 （此处将其作为系统服务安装）
要想使用Memcached做缓存首先需要安装Memcached服务，安装方法如下：
1. 下载Memcached：http://code.jellycan.com/memcached/ 现在的最新版本是1.2.6.注意下载正确的版本，windows 服务的话下载win32 binary。
2.解压之后放在硬盘的目录下，如：D:\memcached. 然后在运行中输入cmd进入命令行，进入到Memcached.exe 所在的目录，例如：D:\memcached,然后输入：Memcached –d install,即可完成安装。
Memcached还有其他的一些常用的命令如下：
-p 监听的端口
-l 连接的IP地址, 默认是本机
-d start 启动memcached服务
-d restart 重起memcached服务
-d stop|shutdown 关闭正在运行的memcached服务
-d install 安装memcached服务
-d uninstall 卸载memcached服务
-u 以的身份运行 (仅在以root运行的时候有效)
-m 最大内存使用，单位MB。默认64MB
-M 内存耗尽时返回错误，而不是删除项
-c 最大同时连接数，默认是1024
-f 块大小增长因子，默认是1.25
-n 最小分配空间，key+value+flags默认是48
-h 显示帮助
按照上面的安装步骤安装之后，使用memcached –m 200来调整最大内存占用之后会发现没有起作用，总是默认的64MB的内存，在网上搜了一下，原因是注册表中并没有写入信息，可以这样来修改。
1. memcached –d shutdown 首先关闭memcached服务。
2.进入注册表，找到HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\memcached Server， 在其中有一个ImagePath项，值为"d:\memcached\memcached.exe" -d runservice，在后面加上-l 127.0.0.1 -m 3000 -c 2048。
3.memcached –d start 启动memcached服务，这样就将memcached的最大内存修改为了3000MB。
对Memcached缓存服务的状态查询，可以先telnet连接上服务：telnet 127.0.0.1 11211 ，然后使用 stats命令查看缓存服务的状态，会返回如下的数据：
time: 1255537291 服务器当前的unix时间戳
total_items: 54 从服务器启动以后存储的items总数量
connection_structures: 19 服务器分配的连接构造数
version: 1.2.6 memcache版本
limit_maxbytes: 67108864 分配给memcache的内存大小（字节）
cmd_get: 1645 get命令（获取）总请求次数
evictions: 0 为获取空闲内存而删除的items数（分配给memcache的空间用满后需
要删除旧的items来得到空间分配给新的items）
total_connections: 19 从服务器启动以后曾经打开过的连接数
bytes: 248723 当前服务器存储items占用的字节数
threads: 1 当前线程数
get_misses: 82 总未命中次数
pointer_size: 32 当前操作系统的指针大小（32位系统一般是32bit）
bytes_read: 490982 总读取字节数（请求字节数）
uptime: 161 服务器已经运行的秒数
curr_connections: 18 当前打开着的连接数
pid: 2816 memcache服务器的进程ID
bytes_written: 16517259 总发送字节数（结果字节数）
get_hits: 1563 总命中次数
cmd_set: 54 set命令（保存）总请求次数
curr_items: 28 服务器当前存储的items数量
二、客户端使用
下载memcached java client：[url]https://github.com/gwhalin/Memcached-Java-Client [/url] 1 解压后将java_memcached-release_2.5.3.jar jar包添加到工程的classpath中
2 利用memcached java client 一个简单的应用
/**
* Copyright (c) 2008 Greg Whalin
* All rights reserved.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the BSD license
*
* This library is distributed in the hope that it will be
* useful, but WITHOUT ANY WARRANTY; without even the implied
* warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
* PURPOSE.
*
* You should have received a copy of the BSD License along with this
* library.
*
* @author Greg Whalin <[email protected]>
*/
package com.danga.MemCached.test;
import java.util.Hashtable;
import com.danga.MemCached.MemCachedClient;
import com.danga.MemCached.SockIOPool;
public class MemcachedTest {
// store results from threads
private static Hashtable<Integer,StringBuilder> threadInfo =
new Hashtable<Integer,StringBuilder>();
/**
* This runs through some simple tests of the MemcacheClient.
*
* Command line args:
* args[0] = number of threads to spawn生产的线程的数目
* args[1] = number of runs per thread 每个线程操作次数
* args[2] = size of object to store
*
* @param args the command line arguments
*/
public static void main(String[] args) {
//String[] serverlist = { "hengtiandesk144:11211", "hengtiandesk144:11212" };
String[] serverlist = { "localhost:11211" };
// initialize the pool for memcache servers
SockIOPool pool = SockIOPool.getInstance();
pool.setServers( serverlist );
pool.setInitConn(5);
pool.setMinConn(5);
pool.setMaxConn(50);
//Set the sleep time between runs of the pool maintenance thread.
pool.setMaintSleep(30);
//Sets the Nagle alg flag for the pool.
pool.setNagle(false);
pool.initialize();
/*int threads = Integer.parseInt(args[0]);
int runs = Integer.parseInt(args[1]);
int size = 1024 * Integer.parseInt(args[2]); // how many kilobytes
*/
int threads = Integer.parseInt("20");
int runs = Integer.parseInt("30");
int size = 1024 * Integer.parseInt("10"); // how many kilobytes
// get object to store
int[] obj = new int[size];
for (int i = 0; i < size; i++) {
obj[i] = i;
}
String[] keys = new String[size];
for (int i = 0; i < size; i++) {
keys[i] = "test_key" + i;
}
for (int i = 0; i < threads; i++) { //模仿连接服务器数目
bench b = new bench(runs, i, obj, keys);
b.start();
}
int i = 0;
while (i < threads) {
if (threadInfo.containsKey(new Integer(i))) {
System.out.println(threadInfo.get( new Integer( i ) ) );
i++;
}
else {
try {
Thread.sleep(1000);
}
catch (InterruptedException e) {
e.printStackTrace();
}
}
}
pool.shutDown();
System.exit(1);
}
/**
* Test code per thread.
*/
private static class bench extends Thread {
private int runs;
private int threadNum;
private int[] object;
private String[] keys;
private int size;
public bench(int runs, int threadNum, int[] object, String[] keys) {
this.runs = runs;
this.threadNum = threadNum;
this.object = object;
this.keys = keys;
this.size = object.length;
}
@SuppressWarnings("deprecation")
public void run() {
//单线程，多线程不安全
StringBuilder result = new StringBuilder();
// get client instance
MemCachedClient mc = new MemCachedClient();
mc.setCompressEnable(false);
mc.setCompressThreshold(0);
// time deletes
long start = System.currentTimeMillis();
for (int i = 0; i < runs; i++) {
mc.delete(keys[i]);
}
long elapse = System.currentTimeMillis() - start;
float avg = (float) elapse / runs;
result.append("\nthread " + threadNum + ": runs: " + runs + " deletes of obj " + (size/1024) + "KB -- avg time per req " + avg + " ms (total: " + elapse + " ms)");
// time stores
start = System.currentTimeMillis();
for (int i = 0; i < runs; i++) {
//System.out.println(keys[i]+object[i]);
mc.set(keys[i], object[i]);
}
elapse = System.currentTimeMillis() - start;
avg = (float) elapse / runs;
result.append("\nthread " + threadNum + ": runs: " + runs + " stores of obj " + (size/1024) + "KB -- avg time per req " + avg + " ms (total: " + elapse + " ms)");
// time gets
start = System.currentTimeMillis();
for (int i = 0; i < runs; i++) {
mc.get(keys[i]);
}
elapse = System.currentTimeMillis() - start;
avg = (float) elapse / runs;
result.append("\nthread " + threadNum + ": runs: " + runs + " gets of obj " + (size/1024) + "KB -- avg time per req " + avg + " ms (total: " + elapse + " ms)");
threadInfo.put(new Integer(threadNum), result);
}
}
}