Do custom gzip compression on mono when returning api responses to avoid a memory leak.

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);
 
-            // 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;
+            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);
@@ -36,6 +46,7 @@ namespace NzbDrone.Common.Http.Dispatchers
             webRequest.AllowAutoRedirect = false;
             webRequest.CookieContainer = cookies;
 
+
             if (request.RequestTimeout != TimeSpan.Zero)
             {
                 webRequest.Timeout = (int)Math.Ceiling(request.RequestTimeout.TotalMilliseconds);
@@ -107,6 +118,19 @@ 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)
                     {

src/Sonarr.Http/Extensions/Pipelines/GZipPipeline.cs

@@ -15,9 +15,14 @@ namespace Sonarr.Http.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 = NzbDrone.Common.EnvironmentInfo.PlatformInfo.IsMono ? WriteGZipStreamMono : (Action<Action<Stream>, Stream>)WriteGZipStream;
         }
 
         public void Register(IPipelines pipelines)
@@ -43,14 +48,7 @@ namespace Sonarr.Http.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 +59,25 @@ namespace Sonarr.Http.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");