在Windows Azure中使用Redis实现进程外缓存

Question

我一直在研究一个网页，该网页显示我在天蓝色云中的数据库中的表。为了减少直接调用数据库以提高性能，我想为页面建立一个缓存。当前，我为表的 读取
保留了一个内存中的缓存（进程内）。现在，我要创建一个进程外缓存，该缓存应在进行 写
操作时进行更新，这意味着插入或更新（因为在更新或添加了一个值之后，内存中缓存将不再有效）。

我被推荐使用Redis，尤其是Book Sleeve，我的问题是在哪里可以找到一些代码示例来帮助我弄清楚如何开始使用它构建进程外缓存并将其组合到当前项目中。

提前致谢

Answer 1

如果你想 单纯 外的过程，那么它是非常简单的-类似于以下，但指出对于BookSleeve被设计为 共享的 ：它完全线程安全的，作为一部多路复用器-
你不应该创建/在每次通话时都要处理它们。还要注意，在这种情况下，我假设您将单独处理序列化，因此我只是公开一个byte[]API：

class MyCache : IDisposable
{
    public void Dispose()
    {
        var tmp = conn;
        conn = null;
        if (tmp != null)
        {
            tmp.Close(true);
            tmp.Dispose();
        }
    }
    private RedisConnection conn;
    private readonly int db;
    public MyCache(string configuration = "127.0.0.1:6379", int db = 0)
    {
        conn = ConnectionUtils.Connect(configuration);
        this.db = db;
        if (conn == null) throw new ArgumentException("It was not possible to connect to redis", "configuration");
    }
    public byte[] Get(string key)
    {
        return conn.Wait(conn.Strings.Get(db, key));
    }
    public void Set(string key, byte[] value, int timeoutSeconds = 60)
    {
        conn.Strings.Set(db, key, value, timeoutSeconds);
    }
}

什么变得 有趣 ，即使用本地内存-如果你想有一个2级高速缓存是 和 进程外的高速缓存，因为现在你需要缓存失效。发布/订阅很方便-
下面显示了这一点。可能并不明显，但这将减少对redis的调用（您可以monitor用来查看此信息）-因为大多数请求都是从本地缓存中处理的。

using BookSleeve;
using System;
using System.Runtime.Caching;
using System.Text;
using System.Threading;

class MyCache : IDisposable
{
    public void Dispose()
    {
        var tmp0 = conn;
        conn = null;
        if (tmp0 != null)
        {
            tmp0.Close(true);
            tmp0.Dispose();
        }

        var tmp1 = localCache;
        localCache = null;
        if (tmp1 != null)
            tmp1.Dispose();

        var tmp2 = sub;
        sub = null;
        if (tmp2 != null)
        {
            tmp2.Close(true);
            tmp2.Dispose();
        }

    }
    private RedisSubscriberConnection sub;
    private RedisConnection conn;
    private readonly int db;
    private MemoryCache localCache;
    private readonly string cacheInvalidationChannel;
    public MyCache(string configuration = "127.0.0.1:6379", int db = 0)
    {
        conn = ConnectionUtils.Connect(configuration);
        this.db = db;
        localCache = new MemoryCache("local:" + db.ToString());
        if (conn == null) throw new ArgumentException("It was not possible to connect to redis", "configuration");
        sub = conn.GetOpenSubscriberChannel();
        cacheInvalidationChannel = db.ToString() + ":inval"; // note that pub/sub is server-wide; use
                                                             // a channel per DB here
        sub.Subscribe(cacheInvalidationChannel, Invalidate);   
    }

    private void Invalidate(string channel, byte[] payload)
    {
        string key = Encoding.UTF8.GetString(payload);
        var tmp = localCache;
        if (tmp != null) tmp.Remove(key);
    }
    private static readonly object nix = new object();
    public byte[] Get(string key)
    {
        // try local, noting the "nix" sentinel value
        object found = localCache[key];
        if (found != null)
        {
            return found == nix ? null : (byte[])found;
        }

        // fetch and store locally
        byte[] blob = conn.Wait(conn.Strings.Get(db, key));
        localCache[key] = blob ?? nix;
        return blob;
    }

    public void Set(string key, byte[] value, int timeoutSeconds = 60, bool broadcastInvalidation = true)
    {
        localCache[key] = value;
        conn.Strings.Set(db, key, value, timeoutSeconds);
        if (broadcastInvalidation)
            conn.Publish(cacheInvalidationChannel, key);
    }
}

static class Program
{
    static void ShowResult(MyCache cache0, MyCache cache1, string key, string caption)
    {
        Console.WriteLine(caption);
        byte[] blob0 = cache0.Get(key), blob1 = cache1.Get(key);
        Console.WriteLine("{0} vs {1}",
            blob0 == null ? "(null)" : Encoding.UTF8.GetString(blob0),
            blob1 == null ? "(null)" : Encoding.UTF8.GetString(blob1)
            );
    }
    public static void Main()
    {
        MyCache cache0 = new MyCache(), cache1 = new MyCache();
        string someRandomKey = "key" + new Random().Next().ToString();
        ShowResult(cache0, cache1, someRandomKey, "Initially");
        cache0.Set(someRandomKey, Encoding.UTF8.GetBytes("hello"));
        Thread.Sleep(10); // the pub/sub is fast, but not *instant*
        ShowResult(cache0, cache1, someRandomKey, "Write to 0");
        cache1.Set(someRandomKey, Encoding.UTF8.GetBytes("world"));
        Thread.Sleep(10); // the pub/sub is fast, but not *instant*
        ShowResult(cache0, cache1, someRandomKey, "Write to 1");
    }
}

请注意，在完整的实现中，您可能希望处理偶尔断开的连接，稍微延迟的重新连接等。