Fix/issue666 (#889)

* cache key now can generate from query string for request with Get Methods and request content for requests with post methods

* MD5Helper Added. OutputCacheMiddleware now can generate cache key using method, url and content

* unit test created for CacheKeyGenerator

* CacheKeyGenerator Registered in OcelotBuilder as singletone

src/Ocelot.Cache.CacheManager/OcelotBuilderExtensions.cs

@@ -33,6 +33,10 @@
             builder.Services.RemoveAll(typeof(IOcelotCache<FileConfiguration>));
             builder.Services.AddSingleton<ICacheManager<FileConfiguration>>(fileConfigCacheManagerOutputCache);
             builder.Services.AddSingleton<IOcelotCache<FileConfiguration>>(fileConfigCacheManager);
+
+            builder.Services.RemoveAll(typeof(ICacheKeyGenerator));
+            builder.Services.AddSingleton<ICacheKeyGenerator, CacheKeyGenerator>();
+
             return builder;
         }
     }

src/Ocelot/Cache/CacheKeyGenerator.cs

@@ -0,0 +1,19 @@
+using System.Text;
+using System.Threading.Tasks;
+using Ocelot.Middleware;
+
+namespace Ocelot.Cache {
+    public class CacheKeyGenerator : ICacheKeyGenerator {
+        public string GenerateRequestCacheKey(DownstreamContext context) {
+            string hashedContent = null;
+            StringBuilder downStreamUrlKeyBuilder = new StringBuilder($"{context.DownstreamRequest.Method}-{context.DownstreamRequest.OriginalString}");
+            if (context.DownstreamRequest.Content != null) {
+                string requestContentString = Task.Run(async () => await context.DownstreamRequest.Content.ReadAsStringAsync()).Result;
+                downStreamUrlKeyBuilder.Append(requestContentString);
+            }
+
+            hashedContent = MD5Helper.GenerateMd5(downStreamUrlKeyBuilder.ToString());
+            return hashedContent;
+        }
+    }
+}

src/Ocelot/Cache/ICacheKeyGenerator.cs

@@ -0,0 +1,7 @@
+using Ocelot.Middleware;
+
+namespace Ocelot.Cache {
+    public interface ICacheKeyGenerator {
+        string GenerateRequestCacheKey(DownstreamContext context);
+    }
+}

src/Ocelot/Cache/MD5Helper.cs

@@ -0,0 +1,22 @@
+using System.Security.Cryptography;
+using System.Text;
+
+namespace Ocelot.Cache {
+    public static class MD5Helper {
+        public static string GenerateMd5(byte[] contentBytes) {
+            MD5 md5 = MD5.Create();
+            byte[] hash = md5.ComputeHash(contentBytes);
+            StringBuilder sb = new StringBuilder();
+            for (int i = 0; i < hash.Length; i++) {
+                sb.Append(hash[i].ToString("X2"));
+            }
+
+            return sb.ToString();
+        }
+
+        public static string GenerateMd5(string contentString) {
+            byte[] contentBytes = Encoding.Unicode.GetBytes(contentString);
+            return GenerateMd5(contentBytes);
+        }
+    }
+}

src/Ocelot/Cache/Middleware/OutputCacheMiddleware.cs

@@ -7,19 +7,23 @@
     using Ocelot.Logging;
     using Ocelot.Middleware;
     using System.IO;
+    using System.Text;
 
     public class OutputCacheMiddleware : OcelotMiddleware
     {
         private readonly OcelotRequestDelegate _next;
         private readonly IOcelotCache<CachedResponse> _outputCache;
+        private readonly ICacheKeyGenerator _cacheGeneratot;
 
         public OutputCacheMiddleware(OcelotRequestDelegate next,
             IOcelotLoggerFactory loggerFactory,
-            IOcelotCache<CachedResponse> outputCache)
+            IOcelotCache<CachedResponse> outputCache,
+            ICacheKeyGenerator cacheGeneratot)
                 :base(loggerFactory.CreateLogger<OutputCacheMiddleware>())
         {
             _next = next;
             _outputCache = outputCache;
+            _cacheGeneratot = cacheGeneratot;
         }
 
         public async Task Invoke(DownstreamContext context)
@@ -31,10 +35,11 @@
             }
 
             var downstreamUrlKey = $"{context.DownstreamRequest.Method}-{context.DownstreamRequest.OriginalString}";
+            string downStreamRequestCacheKey = _cacheGeneratot.GenerateRequestCacheKey(context);
 
             Logger.LogDebug($"Started checking cache for {downstreamUrlKey}");
 
-            var cached = _outputCache.Get(downstreamUrlKey, context.DownstreamReRoute.CacheOptions.Region);
+            var cached = _outputCache.Get(downStreamRequestCacheKey, context.DownstreamReRoute.CacheOptions.Region);
 
             if (cached != null)
             {
@@ -61,12 +66,13 @@
 
             cached = await CreateCachedResponse(context.DownstreamResponse);
 
-            _outputCache.Add(downstreamUrlKey, cached, TimeSpan.FromSeconds(context.DownstreamReRoute.CacheOptions.TtlSeconds), context.DownstreamReRoute.CacheOptions.Region);
+            _outputCache.Add(downStreamRequestCacheKey, cached, TimeSpan.FromSeconds(context.DownstreamReRoute.CacheOptions.TtlSeconds), context.DownstreamReRoute.CacheOptions.Region);
 
             Logger.LogDebug($"finished response added to cache for {downstreamUrlKey}");
         }
 
-        private void SetHttpResponseMessageThisRequest(DownstreamContext context, DownstreamResponse response)
+        private void SetHttpResponseMessageThisRequest(DownstreamContext context, 
+                                                       DownstreamResponse response)
         {
             context.DownstreamResponse = response;
         }

src/Ocelot/DependencyInjection/OcelotBuilder.cs

@@ -107,6 +107,7 @@ namespace Ocelot.DependencyInjection
             Services.TryAddSingleton<IHttpHandlerOptionsCreator, HttpHandlerOptionsCreator>();
             Services.TryAddSingleton<IDownstreamAddressesCreator, DownstreamAddressesCreator>();
             Services.TryAddSingleton<IDelegatingHandlerHandlerFactory, DelegatingHandlerHandlerFactory>();
+            Services.TryAddSingleton<ICacheKeyGenerator, CacheKeyGenerator>();
 
             // see this for why we register this as singleton http://stackoverflow.com/questions/37371264/invalidoperationexception-unable-to-resolve-service-for-type-microsoft-aspnetc
             // could maybe use a scoped data repository

src/Ocelot/Request/Middleware/DownstreamRequest.cs

@@ -19,6 +19,7 @@ namespace Ocelot.Request.Middleware
             Headers = _request.Headers;
             AbsolutePath = _request.RequestUri.AbsolutePath;
             Query = _request.RequestUri.Query;
+            Content = _request.Content;
         }
 
         public HttpRequestHeaders Headers { get; }
@@ -37,6 +38,8 @@ namespace Ocelot.Request.Middleware
 
         public string Query { get; set; }
 
+        public HttpContent Content { get; set; }
+
         public HttpRequestMessage ToHttpRequestMessage()
         {
             var uriBuilder = new UriBuilder