Out-of-process cache injection using Redis in windows azure

Question

I am working on a webpage that displays a table from a database available in my cloudy blue. To reduce the number of calls directly to the database to improve performance, I would like to create a cache for the page. I currently store a cache in memory (in-process) for reading tables. Now I would like to make the cache outside the process, which should be updated from the moment write was created , which means inserts or updates (because after the value is updated or added, the cache in memory will be more invalid).

I was recommended by Redis and, in particular, Book Sleeve, my question is where can I find code samples to help me figure out how to start collecting the cache outside the process with it and combine it in my current project.

Thank you in advance

Answer 1

If you want it purely because of the process, then it's quite simple - something like the following, but noting that BookSleeve is intended for sharing: it is completely thread safe and works as a multiplexer - t create / delete them for each call. Note also that in this context, I assume that you will handle serialization separately, so I just expose the 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); } } 

What is interesting if you need a two-level cache, i.e. using local memory and cache outside the process, since now you need cache invalidation. Pub / sub makes this convenient - the following shows it. This may not be obvious, but it will make far fewer redis calls (you can use monitor to see this) - since most requests are handled by the local cache.

 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"); } } 

Note that with a full implementation, you probably want to handle random connection interruptions, with delayed reconnection, etc.