Fixed: Mono bug causing memory leakage when http connections use gzip compression.

The bug is registered upstream, but this commit works around the problem by doing the gzip decompression separately from the http stack.

Ref #2296

src/NzbDrone.Api/Extensions/Pipelines/GZipPipeline.cs

@@ -5,6 +5,7 @@ using System.Linq;
 using Nancy;
 using Nancy.Bootstrapper;
 using NLog;
+using NzbDrone.Common.EnvironmentInfo;
 using NzbDrone.Common.Extensions;
 
 namespace NzbDrone.Api.Extensions.Pipelines
@@ -15,9 +16,14 @@ namespace NzbDrone.Api.Extensions.Pipelines
 
         public int Order => 0;
 
+        private readonly Action<Action<Stream>, Stream> _writeGZipStream;
+
         public GzipCompressionPipeline(Logger logger)
         {
             _logger = logger;
+
+            // On Mono GZipStream/DeflateStream leaks memory if an exception is thrown, use an intermediate buffer in that case.
+            _writeGZipStream = PlatformInfo.IsMono ? WriteGZipStreamMono : (Action<Action<Stream>, Stream>)WriteGZipStream;
         }
 
         public void Register(IPipelines pipelines)
@@ -43,14 +49,7 @@ namespace NzbDrone.Api.Extensions.Pipelines
                     var contents = response.Contents;
 
                     response.Headers["Content-Encoding"] = "gzip";
-                    response.Contents = responseStream =>
-                    {
-                        using (var gzip = new GZipStream(responseStream, CompressionMode.Compress, true))
-                        using (var buffered = new BufferedStream(gzip, 8192))
-                        {
-                            contents.Invoke(buffered);
-                        }
-                    };
+                    response.Contents = responseStream => _writeGZipStream(contents, responseStream);
                 }
             }
 
@@ -61,6 +60,25 @@ namespace NzbDrone.Api.Extensions.Pipelines
             }
         }
 
+        private static void WriteGZipStreamMono(Action<Stream> innerContent, Stream targetStream)
+        {
+            using (var membuffer = new MemoryStream())
+            {
+                WriteGZipStream(innerContent, membuffer);
+                membuffer.Position = 0;
+                membuffer.CopyTo(targetStream);
+            }
+        }
+
+        private static void WriteGZipStream(Action<Stream> innerContent, Stream targetStream)
+        {
+            using (var gzip = new GZipStream(targetStream, CompressionMode.Compress, true))
+            using (var buffered = new BufferedStream(gzip, 8192))
+            {
+                innerContent.Invoke(buffered);
+            }
+        }
+
         private static bool ContentLengthIsTooSmall(Response response)
         {
             var contentLength = response.Headers.GetValueOrDefault("Content-Length");

src/NzbDrone.Common/Http/Dispatchers/ManagedHttpDispatcher.cs

@@ -1,5 +1,6 @@
 using System;
 using System.IO;
+using System.IO.Compression;
 using System.Net;
 using NzbDrone.Common.EnvironmentInfo;
 using NzbDrone.Common.Extensions;
@@ -25,10 +26,19 @@ namespace NzbDrone.Common.Http.Dispatchers
         {
             var webRequest = (HttpWebRequest)WebRequest.Create((Uri)request.Url);
 
+            if (PlatformInfo.IsMono)
+            {
+                // On Mono GZipStream/DeflateStream leaks memory if an exception is thrown, use an intermediate buffer in that case.
+                webRequest.AutomaticDecompression = DecompressionMethods.None;
+                webRequest.Headers.Add("Accept-Encoding", "gzip");
+            }
+            else
+            {
                 // Deflate is not a standard and could break depending on implementation.
                 // we should just stick with the more compatible Gzip
                 //http://stackoverflow.com/questions/8490718/how-to-decompress-stream-deflated-with-java-util-zip-deflater-in-net
                 webRequest.AutomaticDecompression = DecompressionMethods.GZip;
+            }
             
             webRequest.Method = request.Method.ToString();
             webRequest.UserAgent = _userAgentBuilder.GetUserAgent(request.UseSimplifiedUserAgent);
@@ -107,6 +117,19 @@ namespace NzbDrone.Common.Http.Dispatchers
                     try
                     {
                         data = responseStream.ToBytes();
+
+                        if (PlatformInfo.IsMono && httpWebResponse.ContentEncoding == "gzip")
+                        {
+                            using (var compressedStream = new MemoryStream(data))
+                            using (var gzip = new GZipStream(compressedStream, CompressionMode.Decompress))
+                            using (var decompressedStream = new MemoryStream())
+                            {
+                                gzip.CopyTo(decompressedStream);
+                                data = decompressedStream.ToArray();
+                            }
+
+                            httpWebResponse.Headers.Remove("Content-Encoding");
+                        }
                     }
                     catch (Exception ex)
                     {