Make some Netty Handlers Singletons (#80156)

Some of these handlers can be singletons, they hold no state.
Also, removed some unused fields in the transport.

modules/transport-netty4/src/main/java/org/elasticsearch/http/netty4/Netty4HttpRequest.java

@@ -227,10 +227,6 @@ public class Netty4HttpRequest implements HttpRequest {
         return inboundException;
     }
 
-    public FullHttpRequest nettyRequest() {
-        return request;
-    }
-
     /**
      * A wrapper of {@link HttpHeaders} that implements a map to prevent copying unnecessarily. This class does not support modifications
      * and due to the underlying implementation, it performs case insensitive lookups of key to values.

modules/transport-netty4/src/main/java/org/elasticsearch/http/netty4/Netty4HttpRequestCreator.java

@@ -18,7 +18,11 @@ import org.elasticsearch.ExceptionsHelper;
 import java.util.List;
 
 @ChannelHandler.Sharable
-class Netty4HttpRequestCreator extends MessageToMessageDecoder<FullHttpRequest> {
+final class Netty4HttpRequestCreator extends MessageToMessageDecoder<FullHttpRequest> {
+
+    static final Netty4HttpRequestCreator INSTANCE = new Netty4HttpRequestCreator();
+
+    private Netty4HttpRequestCreator() {}
 
     @Override
     protected void decode(ChannelHandlerContext ctx, FullHttpRequest msg, List<Object> out) {

modules/transport-netty4/src/main/java/org/elasticsearch/http/netty4/Netty4HttpResponseCreator.java

@@ -27,7 +27,11 @@ import java.util.List;
  * Split up large responses to prevent batch compression {@link JdkZlibEncoder} down the pipeline.
  */
 @ChannelHandler.Sharable
-class Netty4HttpResponseCreator extends MessageToMessageEncoder<Netty4HttpResponse> {
+final class Netty4HttpResponseCreator extends MessageToMessageEncoder<Netty4HttpResponse> {
+
+    static final Netty4HttpResponseCreator INSTANCE = new Netty4HttpResponseCreator();
+
+    private Netty4HttpResponseCreator() {}
 
     private static final String DO_NOT_SPLIT = "es.unsafe.do_not_split_http_responses";
 

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

@@ -127,10 +127,6 @@ public class Netty4HttpServerTransport extends AbstractHttpServerTransport {
         Property.NodeScope
     );
 
-    private final ByteSizeValue maxInitialLineLength;
-    private final ByteSizeValue maxHeaderSize;
-    private final ByteSizeValue maxChunkSize;
-
     private final int pipeliningMaxEvents;
 
     private final SharedGroupFactory sharedGroupFactory;
@@ -157,9 +153,6 @@ public class Netty4HttpServerTransport extends AbstractHttpServerTransport {
         NettyAllocator.logAllocatorDescriptionIfNeeded();
         this.sharedGroupFactory = sharedGroupFactory;
 
-        this.maxChunkSize = SETTING_HTTP_MAX_CHUNK_SIZE.get(settings);
-        this.maxHeaderSize = SETTING_HTTP_MAX_HEADER_SIZE.get(settings);
-        this.maxInitialLineLength = SETTING_HTTP_MAX_INITIAL_LINE_LENGTH.get(settings);
         this.pipeliningMaxEvents = SETTING_PIPELINING_MAX_EVENTS.get(settings);
 
         this.maxCompositeBufferComponents = SETTING_HTTP_NETTY_MAX_COMPOSITE_BUFFER_COMPONENTS.get(settings);
@@ -172,9 +165,9 @@ public class Netty4HttpServerTransport extends AbstractHttpServerTransport {
         logger.debug(
             "using max_chunk_size[{}], max_header_size[{}], max_initial_line_length[{}], max_content_length[{}], "
                 + "receive_predictor[{}], max_composite_buffer_components[{}], pipelining_max_events[{}]",
-            maxChunkSize,
-            maxHeaderSize,
-            maxInitialLineLength,
+            SETTING_HTTP_MAX_CHUNK_SIZE.get(settings),
+            SETTING_HTTP_MAX_HEADER_SIZE.get(settings),
+            SETTING_HTTP_MAX_INITIAL_LINE_LENGTH.get(settings),
             maxContentLength,
             receivePredictor,
             maxCompositeBufferComponents,
@@ -297,17 +290,13 @@ public class Netty4HttpServerTransport extends AbstractHttpServerTransport {
     protected static class HttpChannelHandler extends ChannelInitializer<Channel> {
 
         private final Netty4HttpServerTransport transport;
-        private final Netty4HttpRequestCreator requestCreator;
         private final Netty4HttpRequestHandler requestHandler;
-        private final Netty4HttpResponseCreator responseCreator;
         private final HttpHandlingSettings handlingSettings;
 
         protected HttpChannelHandler(final Netty4HttpServerTransport transport, final HttpHandlingSettings handlingSettings) {
             this.transport = transport;
             this.handlingSettings = handlingSettings;
-            this.requestCreator = new Netty4HttpRequestCreator();
             this.requestHandler = new Netty4HttpRequestHandler(transport);
-            this.responseCreator = new Netty4HttpResponseCreator();
         }
 
         @Override
@@ -331,8 +320,8 @@ public class Netty4HttpServerTransport extends AbstractHttpServerTransport {
             if (handlingSettings.isCompression()) {
                 ch.pipeline().addLast("encoder_compress", new HttpContentCompressor(handlingSettings.getCompressionLevel()));
             }
-            ch.pipeline().addLast("request_creator", requestCreator);
-            ch.pipeline().addLast("response_creator", responseCreator);
+            ch.pipeline().addLast("request_creator", Netty4HttpRequestCreator.INSTANCE);
+            ch.pipeline().addLast("response_creator", Netty4HttpResponseCreator.INSTANCE);
             ch.pipeline().addLast("pipelining", new Netty4HttpPipeliningHandler(logger, transport.pipeliningMaxEvents));
             ch.pipeline().addLast("handler", requestHandler);
             transport.serverAcceptedChannel(nettyHttpChannel);

modules/transport-netty4/src/main/java/org/elasticsearch/transport/netty4/ESLoggingHandler.java

@@ -8,13 +8,17 @@
 
 package org.elasticsearch.transport.netty4;
 
+import io.netty.channel.ChannelHandler;
 import io.netty.channel.ChannelHandlerContext;
 import io.netty.handler.logging.LogLevel;
 import io.netty.handler.logging.LoggingHandler;
 
+@ChannelHandler.Sharable
 final class ESLoggingHandler extends LoggingHandler {
 
-    ESLoggingHandler() {
+    static final ESLoggingHandler INSTANCE = new ESLoggingHandler();
+
+    private ESLoggingHandler() {
         super(LogLevel.TRACE);
     }
 

modules/transport-netty4/src/main/java/org/elasticsearch/transport/netty4/Netty4Transport.java

@@ -334,7 +334,7 @@ public class Netty4Transport extends TcpTransport {
             assert ch instanceof Netty4NioSocketChannel;
             NetUtils.tryEnsureReasonableKeepAliveConfig(((Netty4NioSocketChannel) ch).javaChannel());
             ch.pipeline().addLast("byte_buf_sizer", NettyByteBufSizer.INSTANCE);
-            ch.pipeline().addLast("logging", new ESLoggingHandler());
+            ch.pipeline().addLast("logging", ESLoggingHandler.INSTANCE);
             // using a dot as a prefix means this cannot come from any settings parsed
             ch.pipeline().addLast("dispatcher", new Netty4MessageChannelHandler(Netty4Transport.this, recycler));
         }
@@ -362,7 +362,7 @@ public class Netty4Transport extends TcpTransport {
             Netty4TcpChannel nettyTcpChannel = new Netty4TcpChannel(ch, true, name, ch.newSucceededFuture());
             ch.attr(CHANNEL_KEY).set(nettyTcpChannel);
             ch.pipeline().addLast("byte_buf_sizer", NettyByteBufSizer.INSTANCE);
-            ch.pipeline().addLast("logging", new ESLoggingHandler());
+            ch.pipeline().addLast("logging", ESLoggingHandler.INSTANCE);
             ch.pipeline().addLast("dispatcher", new Netty4MessageChannelHandler(Netty4Transport.this, recycler));
             serverAcceptedChannel(nettyTcpChannel);
         }