[8.6] Fix Chunked APIs sending incorrect responses to HEAD requests (#…

…92042) (#92049)

* Fix Chunked APIs sending incorrect responses to HEAD requests (#92042)

Response bodies must always be empty for HEAD requests.
Since the request encoder does not know that its dealing with a response
to a HEAD request we have to indicate this fact to it.
Also, needed to adjust the test http client to use the http-codec so it is able
to correlate what responses are meant for HEAD requests and will correctly read
responses for HEAD requests.
Without this change the added test reproduces the extra bytes and fails with an assert
about more than one response received.

closes #92032

* fix compile

docs/changelog/92042.yaml

@@ -0,0 +1,6 @@
+pr: 92042
+summary: Fix Chunked APIs sending incorrect responses to HEAD requests
+area: Network
+type: bug
+issues:
+ - 92032

modules/transport-netty4/src/main/java/org/elasticsearch/http/netty4/Netty4HttpServerTransport.java

@@ -24,7 +24,9 @@
 import io.netty.handler.codec.http.HttpContentDecompressor;
 import io.netty.handler.codec.http.HttpObjectAggregator;
 import io.netty.handler.codec.http.HttpRequestDecoder;
+import io.netty.handler.codec.http.HttpResponse;
 import io.netty.handler.codec.http.HttpResponseEncoder;
+import io.netty.handler.codec.http.HttpUtil;
 import io.netty.handler.timeout.ReadTimeoutException;
 import io.netty.handler.timeout.ReadTimeoutHandler;
 import io.netty.util.AttributeKey;
@@ -324,7 +326,18 @@ protected void initChannel(Channel ch) throws Exception {
             ch.pipeline()
                 .addLast("decoder", decoder)
                 .addLast("decoder_compress", new HttpContentDecompressor())
-                .addLast("encoder", new HttpResponseEncoder())
+                .addLast("encoder", new HttpResponseEncoder() {
+                    @Override
+                    protected boolean isContentAlwaysEmpty(HttpResponse msg) {
+                        // non-chunked responses (Netty4HttpResponse extends Netty's DefaultFullHttpResponse) with chunked transfer
+                        // encoding are only sent by us in response to HEAD requests and must always have an empty body
+                        if (msg instanceof Netty4HttpResponse netty4HttpResponse && HttpUtil.isTransferEncodingChunked(msg)) {
+                            assert netty4HttpResponse.content().isReadable() == false;
+                            return true;
+                        }
+                        return super.isContentAlwaysEmpty(msg);
+                    }
+                })
                 .addLast("aggregator", aggregator);
             if (handlingSettings.compression()) {
                 ch.pipeline().addLast("encoder_compress", new HttpContentCompressor(handlingSettings.compressionLevel()));

modules/transport-netty4/src/test/java/org/elasticsearch/http/netty4/Netty4HttpClient.java

@@ -21,15 +21,14 @@
 import io.netty.handler.codec.http.DefaultFullHttpRequest;
 import io.netty.handler.codec.http.FullHttpRequest;
 import io.netty.handler.codec.http.FullHttpResponse;
+import io.netty.handler.codec.http.HttpClientCodec;
 import io.netty.handler.codec.http.HttpContentDecompressor;
 import io.netty.handler.codec.http.HttpHeaderNames;
 import io.netty.handler.codec.http.HttpMethod;
 import io.netty.handler.codec.http.HttpObject;
 import io.netty.handler.codec.http.HttpObjectAggregator;
 import io.netty.handler.codec.http.HttpRequest;
-import io.netty.handler.codec.http.HttpRequestEncoder;
 import io.netty.handler.codec.http.HttpResponse;
-import io.netty.handler.codec.http.HttpResponseDecoder;
 import io.netty.handler.codec.http.HttpVersion;
 
 import org.elasticsearch.common.unit.ByteSizeUnit;
@@ -175,8 +174,7 @@ private static class CountDownLatchHandler extends ChannelInitializer<SocketChan
         @Override
         protected void initChannel(SocketChannel ch) {
             final int maxContentLength = new ByteSizeValue(100, ByteSizeUnit.MB).bytesAsInt();
-            ch.pipeline().addLast(new HttpResponseDecoder());
-            ch.pipeline().addLast(new HttpRequestEncoder());
+            ch.pipeline().addLast(new HttpClientCodec());
             ch.pipeline().addLast(new HttpContentDecompressor());
             ch.pipeline().addLast(new HttpObjectAggregator(maxContentLength));
             ch.pipeline().addLast(new SimpleChannelInboundHandler<HttpObject>() {

modules/transport-netty4/src/test/java/org/elasticsearch/http/netty4/Netty4HttpServerTransportTests.java

@@ -40,15 +40,14 @@
 
 import org.elasticsearch.ElasticsearchException;
 import org.elasticsearch.common.bytes.BytesArray;
+import org.elasticsearch.common.collect.Iterators;
 import org.elasticsearch.common.network.NetworkAddress;
 import org.elasticsearch.common.network.NetworkService;
 import org.elasticsearch.common.settings.ClusterSettings;
 import org.elasticsearch.common.settings.Setting;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.transport.TransportAddress;
 import org.elasticsearch.common.unit.ByteSizeValue;
-import org.elasticsearch.common.util.MockPageCacheRecycler;
-import org.elasticsearch.common.util.PageCacheRecycler;
 import org.elasticsearch.common.util.concurrent.ThreadContext;
 import org.elasticsearch.core.TimeValue;
 import org.elasticsearch.http.AbstractHttpServerTransportTestCase;
@@ -57,6 +56,7 @@
 import org.elasticsearch.http.HttpServerTransport;
 import org.elasticsearch.http.HttpTransportSettings;
 import org.elasticsearch.http.NullDispatcher;
+import org.elasticsearch.rest.ChunkedRestResponseBody;
 import org.elasticsearch.rest.RestChannel;
 import org.elasticsearch.rest.RestRequest;
 import org.elasticsearch.rest.RestResponse;
@@ -66,6 +66,7 @@
 import org.elasticsearch.tracing.Tracer;
 import org.elasticsearch.transport.netty4.NettyAllocator;
 import org.elasticsearch.transport.netty4.SharedGroupFactory;
+import org.elasticsearch.xcontent.ToXContent;
 import org.junit.After;
 import org.junit.Before;
 
@@ -94,14 +95,12 @@ public class Netty4HttpServerTransportTests extends AbstractHttpServerTransportT
 
     private NetworkService networkService;
     private ThreadPool threadPool;
-    private PageCacheRecycler recycler;
     private ClusterSettings clusterSettings;
 
     @Before
     public void setup() throws Exception {
         networkService = new NetworkService(Collections.emptyList());
         threadPool = new TestThreadPool("test");
-        recycler = new MockPageCacheRecycler(Settings.EMPTY);
         clusterSettings = randomClusterSettings();
     }
 
@@ -112,7 +111,6 @@ public void shutdown() throws Exception {
         }
         threadPool = null;
         networkService = null;
-        recycler = null;
         clusterSettings = null;
     }
 
@@ -560,6 +558,67 @@ protected void initChannel(SocketChannel ch) {
         }
     }
 
+    public void testHeadRequestToChunkedApi() throws InterruptedException {
+        final HttpServerTransport.Dispatcher dispatcher = new HttpServerTransport.Dispatcher() {
+
+            @Override
+            public void dispatchRequest(final RestRequest request, final RestChannel channel, final ThreadContext threadContext) {
+                try {
+                    channel.sendResponse(
+                        new RestResponse(
+                            OK,
+                            ChunkedRestResponseBody.fromXContent(
+                                () -> Iterators.single(
+                                    (builder, params) -> { throw new AssertionError("should not be called for HEAD REQUEST"); }
+                                ),
+                                ToXContent.EMPTY_PARAMS,
+                                channel
+                            )
+                        )
+                    );
+                } catch (IOException e) {
+                    throw new AssertionError(e);
+                }
+            }
+
+            @Override
+            public void dispatchBadRequest(final RestChannel channel, final ThreadContext threadContext, final Throwable cause) {
+                throw new AssertionError();
+            }
+
+        };
+
+        final Settings settings = createSettings();
+        try (
+            Netty4HttpServerTransport transport = new Netty4HttpServerTransport(
+                settings,
+                networkService,
+                threadPool,
+                xContentRegistry(),
+                dispatcher,
+                clusterSettings,
+                new SharedGroupFactory(settings),
+                Tracer.NOOP
+            )
+        ) {
+            transport.start();
+            final TransportAddress remoteAddress = randomFrom(transport.boundAddress().boundAddresses());
+
+            try (Netty4HttpClient client = new Netty4HttpClient()) {
+                final String url = "/some-head-endpoint";
+                final FullHttpRequest request = new DefaultFullHttpRequest(HttpVersion.HTTP_1_1, HttpMethod.HEAD, url);
+
+                final FullHttpResponse response = client.send(remoteAddress.address(), request);
+                try {
+                    assertThat(response.status(), equalTo(HttpResponseStatus.OK));
+                    assertFalse(response.content().isReadable());
+                } finally {
+                    response.release();
+                }
+            }
+        }
+    }
+
     private Settings createSettings() {
         return createBuilderWithPort().build();
     }