[KNOX-3248] Knox Gateway + Livy HA mode gzip exception results in duplicated requests and unneeded failovers (#1143)

Author: nileshrathi345

gateway-provider-rewrite/src/main/java/org/apache/knox/gateway/filter/rewrite/impl/UrlRewriteResponse.java

@@ -187,7 +187,7 @@ public void streamResponse( InputStream input, OutputStream output ) throws IOEx
       inBuffer.reset();
 
       final InputStream unFilteredStream;
-      if(isGzip || "gzip".equalsIgnoreCase(contentEncoding)) {
+      if(isGzip) {
         unFilteredStream = new GzipCompressorInputStream(inBuffer, true);
         outStream = new GZIPOutputStream(output, STREAM_BUFFER_SIZE);
       } else if ("deflate".equalsIgnoreCase(contentEncoding)) {

gateway-provider-rewrite/src/test/java/org/apache/knox/gateway/filter/rewrite/impl/UrlRewriteResponseTest.java

@@ -165,6 +165,45 @@ public void testStreamResponse() throws IOException {
     testStreamResponse(content, rewriteResponse, "deflate");
   }
 
+  @Test
+  public void testStreamEmptyGzipResponse() throws IOException {
+    UrlRewriteProcessor rewriter = EasyMock.createNiceMock(UrlRewriteProcessor.class);
+    EasyMock.expect(rewriter.getConfig()).andReturn(null).anyTimes();
+
+    ServletContext context = EasyMock.createNiceMock(ServletContext.class);
+    EasyMock.expect(context.getAttribute(
+                    UrlRewriteServletContextListener.PROCESSOR_ATTRIBUTE_NAME))
+            .andReturn(rewriter).anyTimes();
+
+    FilterConfig config = EasyMock.createNiceMock(FilterConfig.class);
+    EasyMock.expect(config.getInitParameter(
+                    UrlRewriteServletFilter.RESPONSE_BODY_FILTER_PARAM))
+            .andReturn("test-filter").anyTimes();
+    EasyMock.expect(config.getServletContext()).andReturn(context).anyTimes();
+
+    HttpServletRequest request = EasyMock.createNiceMock(HttpServletRequest.class);
+    EasyMock.expect(request.getContentType()).andReturn("application/json").anyTimes();
+
+    HttpServletResponse response = EasyMock.createNiceMock(HttpServletResponse.class);
+    EasyMock.expect(response.getContentType()).andReturn("application/json").anyTimes();
+
+    EasyMock.replay(rewriter, context, config, request, response);
+
+    UrlRewriteResponse rewriteResponse =
+            new UrlRewriteResponse(config, request, response);
+
+    rewriteResponse.setHeader("Content-Encoding", "gzip");
+
+    Path emptyInput = Files.createTempFile("empty", "input");
+    Path output = Files.createTempFile("output", "test");
+
+    try (InputStream in = Files.newInputStream(emptyInput);
+         OutputStream out = Files.newOutputStream(output)) {
+
+      rewriteResponse.streamResponse(in, out);
+    }
+  }
+
   private void testStreamResponse(String content, UrlRewriteResponse rewriteResponse, String contentType) throws IOException {
     Path inputFile = Files.createTempFile("input", "test");
     Path outputFile = Files.createTempFile("output", "test");