Fix gzip compression when running on .NET core (#2154)

- Content-Encoding was being added to the wrong header
 - Stream was being closed pre-maturely

Closes #2150

Author: gmarz

src/Elasticsearch.Net/Connection/HttpConnection-CoreFx.cs

@@ -144,29 +144,28 @@ protected virtual HttpRequestMessage CreateRequestMessage(RequestData requestDat
 			if (data != null)
 			{
 				var stream = requestData.MemoryStreamFactory.Create();
-
+				requestMessage.Content = new StreamContent(stream);
 				if (requestData.HttpCompression)
 				{
-					using (var zipStream = new GZipStream(stream, CompressionMode.Compress))
-						data.Write(zipStream, requestData.ConnectionSettings);
-
-					requestMessage.Headers.Add("Content-Encoding", "gzip");
+					requestMessage.Content.Headers.Add("Content-Encoding", "gzip");
 					requestMessage.Headers.AcceptEncoding.Add(new StringWithQualityHeaderValue("gzip"));
 					requestMessage.Headers.AcceptEncoding.Add(new StringWithQualityHeaderValue("deflate"));
+					using (var zipStream = new GZipStream(stream, CompressionMode.Compress, true))
+						data.Write(zipStream, requestData.ConnectionSettings);
 				}
 				else
 					data.Write(stream, requestData.ConnectionSettings);
-
 				stream.Position = 0;
-				requestMessage.Content = new StreamContent(stream);
 			}
 			else
 			{
 				// Set content in order to set a Content-Type header.
 				// Content gets diposed so can't be shared instance
 				requestMessage.Content = new ByteArrayContent(new byte[0]);
 			}
+
 			requestMessage.Content.Headers.ContentType = new MediaTypeHeaderValue(requestData.ContentType);
+
 			return requestMessage;
 		}
 

src/Tests/ClientConcepts/Connection/HttpConnectionTests.cs

@@ -0,0 +1,38 @@
+using FluentAssertions;
+using Nest;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Tests.Framework;
+using Tests.Framework.Integration;
+using Tests.Framework.MockData;
+using Xunit;
+
+namespace Tests.ClientConcepts.Connection
+{
+	[Collection(IntegrationContext.ReadOnly)]
+	public class HttpConnectionTests
+	{
+		ReadOnlyCluster _cluster;
+
+		public HttpConnectionTests(ReadOnlyCluster cluster, EndpointUsage usage)
+		{
+			_cluster = cluster;
+		}
+
+		[I]
+		public void HttpCompression()
+		{
+			var client = _cluster.Client(s => s.EnableHttpCompression());
+			var response = client.Search<Project>(s => s
+				.Index("project")
+				.Query(q => q
+					.Term("foo", "bar")
+				)
+			);
+			response.IsValid.Should().BeTrue();
+		}
+	}
+}

src/Tests/Framework/Integration/Process/ElasticsearchNode.cs

@@ -135,6 +135,7 @@ bool shieldEnabled
 				$"es.path.repo={this.RepositoryPath}",
 				$"es.script.inline=on",
 				$"es.script.indexed=on",
+				$"es.http.compression=true",
 				$"es.node.{attr}testingcluster=true",
 				$"es.shield.enabled=" + (shieldEnabled ? "true" : "false")
 			};

src/Tests/Tests.csproj

@@ -541,6 +541,7 @@
     <Compile Include="ClientConcepts\ConnectionPooling\RequestOverrides\RequestTimeoutsOverrides.doc.cs" />
     <Compile Include="ClientConcepts\ConnectionPooling\RequestOverrides\RespectsAllowedStatusCode.doc.cs" />
     <Compile Include="ClientConcepts\ConnectionPooling\RequestOverrides\RespectsForceNode.doc.cs" />
+    <Compile Include="ClientConcepts\Connection\HttpConnectionTests.cs" />
     <Compile Include="ClientConcepts\HighLevel\Caching\FieldResolverCacheTests.cs" />
     <Compile Include="ClientConcepts\HighLevel\Inference\DocumentPaths.doc.cs" />
     <Compile Include="ClientConcepts\HighLevel\Inference\FeaturesInference.doc.cs" />