Windows上memcached的使用

时间 2019-11-09

原文原文链接

Memcached是什么?
Memcached是由Danga Interactive开发的，高性能的，分布式的内存对象缓存系统，用于在动态应用中减小数据库负载，提高访问速度。html

Memcached能缓存什么？
经过在内存里维护一个统一的巨大的hash表，Memcached可以用来存储各类格式的数据，包括图像、视频、文件以及数据库检索的结果等。
Memcached快么？
很是快。Memcached使用了libevent（若是能够的话，在linux下使用epoll）来均衡任何数量的打开连接，使用非阻塞的网络I/O，对内部对象实现引用计数(所以，针对多样的客户端，对象能够处在多样的状态)，使用本身的页块分配器和哈希表，所以虚拟内存不会产生碎片而且虚拟内存分配的时间复杂度能够保证为O(1).。
Memcached的特色？
Memcached的缓存是一种分布式的，可让不一样主机上的多个用户同时访问，所以解决了共享内存只能单机应用的局限，更不会出现使用数据库作相似事情的时候，磁盘开销和阻塞的发生。linux

Memcached的使用须要服务端和客户端同时合做完成。算法

服务端通常用Danga Interactive开发的：数据库

Memcached官方站点：http://www.danga.com/memcached/windows

Memcached Win32 1.2.6下载：http://code.jellycan.com/memcached/ 或者 http://code.google.com/p/beitmemcached/（windows）缓存

1.解压Memcached_1.2.5.zip ，它是memcached的服务器端。
2.把Memcached_1.2.5复制到你指定的作为缓存服务器的电脑上，好比叫作192.168.0.1。
3.cmd下运行相似命令 'd:/memcached/memcached.exe -d install' 安装服务器端，这时候它应该会出如今windows服务中
4.cmd下运行相似命令 'd:/memcached/memcached.exe -d start'启动服务，看服务器进程中是否有memcached进程。
5.确认服务器端口11211是否开放（防火墙设置中），不然其余机器没法访问
6.服务器端这时已经安装完毕、在其余机器上测试一下，cmd输入telnet 192.168.0.1 11211看可否登陆服务器

telnet添加数据到memcached：网络

add key值 0 时间(秒) 长度(存放多长时间由你指定, 键名不能重复，可是值能够重复app

）例：add name 0 5 5不能够在add name 0 77 44socket

获取数据

get key值【key-val key不能重复，可是val能够重复】

修改数据

replace key值 0 60 5 【若是key值不存在，则失败】

set key值 0 60 5 【若是key值不存在，至关于添加，若是存在，则至关于修改.】

删除数据

delete 键值

例：

至此服务端配置完成

客户端的版本比较多，而且不能互用，由于采用了压缩机制，日志等功能，因此在选择客户端时要注意这些。

Memcached .NET客户端：

1).NET memcached client library

　　下载地址：https://sourceforge.net/projects/memcacheddotnet

2）enyim.com Memcached Client

　　下载地址：http://www.codeplex.com/EnyimMemcached/

3）Memcached Providers

　　下载地址：http://www.codeplex.com/memcachedproviders

4) BeIT Memcached

　　下载地址：http://code.google.com/p/beitmemcached/

我这里用BeIT，BeITMemcached_source_2008_05_31.zip压缩包下栽下来，里面有Sample

class Example {
        public static void Main(string[] args) {
            //---------------------
            // Setting up a client.
            //---------------------
            Console.Out.WriteLine("Setting up Memcached Client.");
            MemcachedClient.Setup("MyCache", new string[] { "localhost" });

            //It is possible to have several clients with different configurations:
            //If it is impossible to resolve the hosts, this method will throw an exception.
            try {
                MemcachedClient.Setup("MyOtherCache", new string[]{ "server1.example.com:12345", "server2.example.com:12345"});
            } catch (Exception e) {
                Console.WriteLine(e.Message);
            }

            //Get the instance we just set up so we can use it. You can either store this reference yourself in
            //some field, or fetch it every time you need it, it doesn't really matter.
            MemcachedClient cache = MemcachedClient.GetInstance("MyCache");

            //It is also possible to set up clients in the standard config file. Check the section "beitmemcached" 
            //in the App.config file in this project and you will see that a client called "MyConfigFileCache" is defined.
            MemcachedClient configFileCache = MemcachedClient.GetInstance("MyConfigFileCache");

            //Change client settings to values other than the default like this:
            cache.SendReceiveTimeout = 5000;
            cache.ConnectTimeout = 5000;
            cache.MinPoolSize = 1;
            cache.MaxPoolSize = 5;

            //----------------
            // Using a client.
            //----------------

            //Set some items
            Console.Out.WriteLine("Storing some items.");
            cache.Set("mystring", "The quick brown fox jumped over the lazy dog.");
            cache.Set("myarray", new string[]{"This is the first string.", "This is the second string."});
            cache.Set("myinteger", 4711);
            cache.Set("mydate", new DateTime(2008, 02, 23));
            //Use custom hash
            cache.Set("secondstring", "Flygande b鋍kasiner s鰇a hwila p?mjuka tufvor", 4711);

            //Get a string
            string str = cache.Get("mystring") as string;
            if (str != null) {
                Console.Out.WriteLine("Fetched item with key: mystring, value: " + str);
            }

            //Get an object
            string[] array = cache.Get("myarray") as string[];
            if (array != null) {
                Console.Out.WriteLine("Fetched items with key: myarray, value 1: " + array[0] + ", value 2: " + array[1]);
            }

            //Get several values at once
            object[] result = cache.Get(new string[]{"myinteger", "mydate"});
            if (result[0] != null && result[0] is int) {
                Console.Out.WriteLine("Fetched item with key: myinteger, value: " + (int)result[0]);
            }
            if (result[1] != null && result[1] is DateTime) {
                Console.Out.WriteLine("Fetched item with key: mydate, value: " + (DateTime)result[1]);
            }

            str = cache.Get("secondstring", 4711) as string;
            if (str != null) {
                Console.Out.WriteLine("Fetched item with key and custom hash: secondstring, value: " + str);
            }

            //Set a counter
            Console.Out.WriteLine("Setting an item for incrementing and decrementing.");
            cache.SetCounter("mycounter", 9000);
            ulong? counter = cache.GetCounter("mycounter");
            if (counter.HasValue) {
                Console.Out.WriteLine("Fetched mycounter, value: " + counter.Value);
            }

            //Increment the counter
            counter = cache.Increment("mycounter", 1);
            if (counter.HasValue) {
                Console.Out.WriteLine("Incremented mycounter with 1, new value: " + counter.Value);
            }

            //Decrement the counter
            counter = cache.Decrement("mycounter", 9000);
            if (counter.HasValue) {
                Console.Out.WriteLine("Decremented mycounter with 9000, new value: " + counter.Value);
            }

            //Append and prepend
            Console.Out.WriteLine("Storing bar for append/prepend");
            cache.Set("foo", "bar");
            Console.Out.WriteLine("Appending baz");
            cache.Append("foo", " baz");
            Console.Out.WriteLine("Prepending foo");
            cache.Prepend("foo", "foo ");
            Console.Out.WriteLine("New value: " + cache.Get("foo"));

            //Cas
            cache.Delete("castest");
            Console.Out.WriteLine("Trying to CAS non-existant key castest: " + cache.CheckAndSet("castest", "a", 0));
            Console.Out.WriteLine("Setting value for key: castest, value: a");
            cache.Set("castest", "a");
            Console.Out.WriteLine("Trying to CAS key castest with the wrong unique: " + cache.CheckAndSet("castest", "a", 0));
            ulong unique;
            cache.Gets("castest", out unique);
            Console.Out.WriteLine("Getting cas unique for key castest: " + unique);
            Console.Out.WriteLine("Trying to CAS again with the above unique: " + cache.CheckAndSet("castest", "b", unique));
            string value = cache.Gets("castest", out unique) as string;
            Console.Out.WriteLine("New value: " + value + ", new unique: " + unique);

            Console.Out.WriteLine("Displaying the socketpool status:");
            foreach (KeyValuePair<string, Dictionary<string, string>> host in cache.Status()) {
                Console.Out.WriteLine("Host: " + host.Key);
                foreach (KeyValuePair<string, string> item in host.Value) {
                    Console.Out.WriteLine("\t" + item.Key + ": " + item.Value);
                }
                Console.Out.WriteLine();
            }

            Console.Out.WriteLine();
            Console.Out.WriteLine("Finished. Press enter to exit.");
            Console.In.ReadLine();
        }
    }

最先的客户端是采用取余的hash算法来查找服务器的，咱们知道以往资料要放到 M 台服务器上，最简单的方法就是取余数 (hash_value % M) 而后放到对应的服务器上，那就是当添加或移除服务器时，缓存重组的代价至关巨大。添加服务器后，余数就会产生巨变，这样就没法获取与保存时相同的服务器，从而影响缓存的命中率。
现在采用了Consistent Hashing算法来改善性能，具体能够看最后的参考网址。

参考

http://blog.csdn.net/jinjazz/article/details/2664136

http://www.cnblogs.com/dudu/archive/2009/07/19/1526407.html

http://www.cnblogs.com/mecity/archive/2011/06/13/2079548.html

http://www.cnblogs.com/wucg/archive/2011/03/01/1968185.html

http://blog.csdn.net/whjwhja6/article/details/9172463

http://blog.csdn.net/hguisu/article/details/7353551