实战Memcached缓存系统(5)Memcached的CAS程序实例
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1. 非CAS
首先看一个不是CAS的Memcached程序实例。实例的问题原型,见上一篇博文。
程序实例:
- package com.sinosuperman.memcached;
-
- import java.io.IOException;
- import java.net.InetSocketAddress;
-
- import net.spy.memcached.MemcachedClient;
-
- public class Test {
- public static void main(String[] args) throws IOException {
- MemcachedClient cache = new MemcachedClient(new InetSocketAddress("127.0.0.1", 11211));
-
- cache.set("x", 1800, "Love");
-
- String obj1 = (String) cache.get("x");
- String obj2 = (String) cache.get("x");
- obj2 = "Michael";
-
- cache.set("x", 1800, obj2);
- System.out.println("Non-CAS 2:\t" + obj2);
- System.out.println("Non-CAS 1:\t" + obj1);
- }
- }
运行结果:
- 2011-12-18 23:12:39.836 INFO net.spy.memcached.MemcachedConnection: Added {QA sa=/127.0.0.1:11211, #Rops=0, #Wops=0, #iq=0, topRop=null, topWop=null, toWrite=0, interested=0} to connect queue
- 2011-12-18 23:12:39.843 INFO net.spy.memcached.MemcachedConnection: Connection state changed for sun.nio.ch.SelectionKeyImpl@b09e89
- Non-CAS 2: Michael
- Non-CAS 1: Love
可见在多个Client操作时,一定会引起写不一致性的问题。
2. CAS
程序实例:
- package com.sinosuperman.memcached;
-
- import java.io.IOException;
- import java.net.InetSocketAddress;
-
- import net.spy.memcached.CASValue;
- import net.spy.memcached.MemcachedClient;
-
- public class Test {
- @SuppressWarnings("unchecked")
- public static void main(String[] args) throws IOException {
- MemcachedClient cache = new MemcachedClient(new InetSocketAddress("127.0.0.1", 11211));
-
- cache.set("y", 1800, "Michael");
-
- CASValue casValue1 = cache.gets("y");
- CASValue casValue2 = cache.gets("y");
- cache.cas("y", casValue2.getCas(), "Love");
-
- System.out.println("CAS 2:\t" + casValue2.getCas());
- System.out.println("Value 2:\t" + casValue2.getValue());
-
- System.out.println("CAS 1:\t" + casValue1.getCas());
- System.out.println("Value 1:\t" + casValue1.getValue());
- }
- }
运行结果:- 2011-12-18 23:07:14.528 INFO net.spy.memcached.MemcachedConnection: Added {QA sa=/127.0.0.1:11211, #Rops=0, #Wops=0, #iq=0, topRop=null, topWop=null, toWrite=0, interested=0} to connect queue
- 2011-12-18 23:07:14.541 INFO net.spy.memcached.MemcachedConnection: Connection state changed for sun.nio.ch.SelectionKeyImpl@1621e42
- CAS 2: 11
- Value 2: Love
- CAS 1: 11
- Value 1: Love
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