Revert "Replace auto-read with proper flow-control in HTTP pipeline (#127259)" (#127403)

This reverts commit 3cf7061 and unmutes
the associated tests

Closes #127391
Closes #127392

Author: DaveCTurner

docs/changelog/127259.yaml

@@ -205,6 +205,7 @@ public void testClientConnectionCloseMidStream() throws Exception {
 
             // await stream handler is ready and request full content
             var handler = clientContext.awaitRestChannelAccepted(opaqueId);
+            assertBusy(() -> assertNotEquals(0, handler.stream.bufSize()));
 
             assertFalse(handler.isClosed());
 
@@ -214,6 +215,7 @@ public void testClientConnectionCloseMidStream() throws Exception {
             assertEquals(requestTransmittedLength, handler.readUntilClose());
 
             assertTrue(handler.isClosed());
+            assertEquals(0, handler.stream.bufSize());
         }
     }
 
@@ -230,6 +232,7 @@ public void testServerCloseConnectionMidStream() throws Exception {
 
             // await stream handler is ready and request full content
             var handler = clientContext.awaitRestChannelAccepted(opaqueId);
+            assertBusy(() -> assertNotEquals(0, handler.stream.bufSize()));
             assertFalse(handler.isClosed());
 
             // terminate connection on server and wait resources are released
@@ -238,6 +241,7 @@ public void testServerCloseConnectionMidStream() throws Exception {
             handler.channel.request().getHttpChannel().close();
             assertThat(safeGet(exceptionFuture), instanceOf(ClosedChannelException.class));
             assertTrue(handler.isClosed());
+            assertBusy(() -> assertEquals(0, handler.stream.bufSize()));
         }
     }
 
@@ -253,6 +257,7 @@ public void testServerExceptionMidStream() throws Exception {
 
             // await stream handler is ready and request full content
             var handler = clientContext.awaitRestChannelAccepted(opaqueId);
+            assertBusy(() -> assertNotEquals(0, handler.stream.bufSize()));
             assertFalse(handler.isClosed());
 
             // terminate connection on server and wait resources are released
@@ -264,6 +269,7 @@ public void testServerExceptionMidStream() throws Exception {
             final var exception = asInstanceOf(RuntimeException.class, safeGet(exceptionFuture));
             assertEquals(ServerRequestHandler.SIMULATED_EXCEPTION_MESSAGE, exception.getMessage());
             safeAwait(handler.closedLatch);
+            assertBusy(() -> assertEquals(0, handler.stream.bufSize()));
         }
     }
 
@@ -304,7 +310,7 @@ public void testClientBackpressure() throws Exception {
                 });
                 handler.readBytes(partSize);
             }
-            assertTrue(handler.receivedLastChunk);
+            assertTrue(handler.stream.hasLast());
         }
     }
 

modules/transport-netty4/src/internalClusterTest/java/org/elasticsearch/http/netty4/Netty4IncrementalRequestHandlingIT.java

@@ -15,7 +15,6 @@
 import io.netty.handler.codec.http.HttpObjectAggregator;
 import io.netty.handler.codec.http.HttpRequest;
 import io.netty.handler.codec.http.HttpRequestDecoder;
-import io.netty.handler.codec.http.LastHttpContent;
 
 import org.elasticsearch.http.HttpPreRequest;
 import org.elasticsearch.http.netty4.internal.HttpHeadersAuthenticatorUtils;
@@ -49,9 +48,6 @@ public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception
         }
         if (aggregating || msg instanceof FullHttpRequest) {
             super.channelRead(ctx, msg);
-            if (msg instanceof LastHttpContent == false) {
-                ctx.read(); // HttpObjectAggregator is tricky with auto-read off, it might not call read again, calling on its behalf
-            }
         } else {
             streamContentSizeHandler.channelRead(ctx, msg);
         }

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

@@ -123,7 +123,6 @@ private void handleRequest(ChannelHandlerContext ctx, HttpRequest request) {
                 isContinueExpected = true;
             } else {
                 ctx.writeAndFlush(EXPECTATION_FAILED_CLOSE.retainedDuplicate()).addListener(ChannelFutureListener.CLOSE);
-                ctx.read();
                 return;
             }
         }
@@ -137,7 +136,6 @@ private void handleRequest(ChannelHandlerContext ctx, HttpRequest request) {
                 decoder.reset();
             }
             ctx.writeAndFlush(TOO_LARGE.retainedDuplicate()).addListener(ChannelFutureListener.CLOSE_ON_FAILURE);
-            ctx.read();
         } else {
             ignoreContent = false;
             currentContentLength = 0;
@@ -152,13 +150,11 @@ private void handleRequest(ChannelHandlerContext ctx, HttpRequest request) {
     private void handleContent(ChannelHandlerContext ctx, HttpContent msg) {
         if (ignoreContent) {
             msg.release();
-            ctx.read();
         } else {
             currentContentLength += msg.content().readableBytes();
             if (currentContentLength > maxContentLength) {
                 msg.release();
                 ctx.writeAndFlush(TOO_LARGE_CLOSE.retainedDuplicate()).addListener(ChannelFutureListener.CLOSE);
-                ctx.read();
             } else {
                 ctx.fireChannelRead(msg);
             }