Added some basic cache stuff

src/Ocelot/Cache/Middleware/OutputCacheMiddleware.cs

@@ -0,0 +1,69 @@
+using System;
+using System.Net.Http;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.Logging;
+using Ocelot.Infrastructure.RequestData;
+using Ocelot.Middleware;
+
+namespace Ocelot.Cache.Middleware
+{
+    public class OutputCacheMiddleware : OcelotMiddleware
+    {
+        private readonly RequestDelegate _next;
+        private readonly ILogger _logger;
+        private readonly IOcelotCache<HttpResponseMessage> _outputCache;
+
+        public OutputCacheMiddleware(RequestDelegate next, 
+            ILoggerFactory loggerFactory,
+            IRequestScopedDataRepository scopedDataRepository,
+            IOcelotCache<HttpResponseMessage> outputCache)
+            :base(scopedDataRepository)
+        {
+            _next = next;
+            _outputCache = outputCache;
+            _logger = loggerFactory.CreateLogger<OutputCacheMiddleware>();
+        }
+
+        public async Task Invoke(HttpContext context)
+        {
+            var downstreamUrlKey = DownstreamUrl;
+
+            if (!DownstreamRoute.ReRoute.IsCached)
+            {
+                await _next.Invoke(context);
+                return;
+            }
+
+            _logger.LogDebug("OutputCacheMiddleware.Invoke stared checking cache for downstreamUrlKey", downstreamUrlKey);
+  
+            var cached = _outputCache.Get(downstreamUrlKey);
+
+            if (cached != null)
+            {
+                SetHttpResponseMessageThisRequest(cached);
+
+                _logger.LogDebug("OutputCacheMiddleware.Invoke finished returned cached response for downstreamUrlKey", downstreamUrlKey);
+
+                return;
+            }
+
+            _logger.LogDebug("OutputCacheMiddleware.Invoke no resonse cached for downstreamUrlKey", downstreamUrlKey);
+
+            await _next.Invoke(context);
+
+            if (PipelineError())
+            {
+                _logger.LogDebug("OutputCacheMiddleware.Invoke there was a pipeline error for downstreamUrlKey", downstreamUrlKey);
+
+                return;
+            }
+
+            var response = HttpResponseMessage;
+
+            _outputCache.Add(downstreamUrlKey, response, TimeSpan.FromSeconds(DownstreamRoute.ReRoute.FileCacheOptions.TtlSeconds));
+
+            _logger.LogDebug("OutputCacheMiddleware.Invoke finished response added to cache for downstreamUrlKey", downstreamUrlKey);
+        }
+    }
+}