From 2c64f235332d17ab510040cebc3db951310f9ad7 Mon Sep 17 00:00:00 2001 From: Pavel Ptashyts <49400901+pavel-ptashyts@users.noreply.github.com> Date: Fri, 28 Aug 2026 08:31:56 +0200 Subject: [PATCH] Mark an HTTP/2 connection instead of looking isHttp2 asked the pipeline for the multiplex handler by name, and the write path asks isHttp2 of every request: once to decide whether to store the per-request future on the channel, once to route the write. A pipeline lookup walks the handlers comparing names, and an HTTP/1.1 connection, having no such handler, is walked to the end to say no, which is the common case for anyone not using HTTP/2. In one profile of a client with HTTP/2 disabled, DefaultChannelPipeline.context0 took 83 CPU samples on that account alone. The multiplex handler is installed in exactly one place, so a channel attribute is set beside it and isHttp2 reads that: a binary search over integer keys in a small array rather than a walk with a string compare per handler. hasAttr rather than attr().get(), which would add an entry to the attribute map of every HTTP/1.1 channel just to find none. Not a config check. Reading isHttp2Enabled first would be cheaper still, but the two can disagree: NettyConnectListener upgrades on the ALPN result alone, and a caller who supplies an SslContext or an SslEngineFactory of their own controls what ALPN advertises whatever the config says - which the WebSocket guard beside it already accounts for. A request would then be written as HTTP/1.1 onto an HTTP/2 pipeline. The attribute costs nothing extra and cannot disagree, since it is set where the handler is. The attribute cannot go stale either: nothing removes the multiplex handler from a pipeline, so there is no downgrade for the two to differ across. ChannelManagerHttp2MarkerTest pins them together, so a later change to the upgrade cannot set one without the other. Removing the attribute fails that test and 46 of the 52 in BasicHttp2Test, the write path having routed HTTP/2 connections down the HTTP/1.1 branch. Claude Code on behalf of Pavel Ptashyts Co-Authored-By: Claude Opus 5 --- .../netty/channel/ChannelManager.java | 14 +++- .../ChannelManagerHttp2MarkerTest.java | 84 +++++++++++++++++++ 2 files changed, 96 insertions(+), 2 deletions(-) create mode 100644 client/src/test/java/org/asynchttpclient/netty/channel/ChannelManagerHttp2MarkerTest.java diff --git a/client/src/main/java/org/asynchttpclient/netty/channel/ChannelManager.java b/client/src/main/java/org/asynchttpclient/netty/channel/ChannelManager.java index f305fb3f3..95ce64f57 100755 --- a/client/src/main/java/org/asynchttpclient/netty/channel/ChannelManager.java +++ b/client/src/main/java/org/asynchttpclient/netty/channel/ChannelManager.java @@ -58,6 +58,7 @@ import io.netty.resolver.AddressResolver; import io.netty.resolver.AddressResolverGroup; import io.netty.resolver.NameResolver; +import io.netty.util.AttributeKey; import io.netty.util.Timer; import io.netty.util.concurrent.DefaultThreadFactory; import io.netty.util.concurrent.Future; @@ -125,6 +126,8 @@ public class ChannelManager { public static final String LOGGING_HANDLER = "logging"; public static final String HTTP2_FRAME_CODEC = "http2-frame-codec"; public static final String HTTP2_MULTIPLEX = "http2-multiplex"; + // Set beside HTTP2_MULTIPLEX and nowhere else, so that isHttp2 can answer without a pipeline lookup. + private static final AttributeKey HTTP2_CONNECTION_ATTRIBUTE = AttributeKey.valueOf("http2Connection"); public static final String AHC_HTTP2_HANDLER = "ahc-http2"; private static final String TARGET_SSL_HANDLER = "target-ssl"; private static final Logger LOGGER = LoggerFactory.getLogger(ChannelManager.class); @@ -1027,10 +1030,16 @@ protected void initChannel(Channel channel) throws Exception { } /** - * Checks whether the given channel is an HTTP/2 connection (i.e. has the HTTP/2 multiplex handler installed). + * Checks whether the given channel is an HTTP/2 connection: the parent that multiplexes streams, not one of + * its stream children, whose own pipelines carry neither the multiplex handler nor this attribute. + *

+ * Answered from an attribute rather than by looking {@link #HTTP2_MULTIPLEX} up in the pipeline. The two are + * set together and so always agree, but a pipeline lookup compares handler names down the chain, and an + * HTTP/1.1 connection, which has no such handler, is walked to the end to say no. The write path asks this + * of every request. */ public static boolean isHttp2(Channel channel) { - return channel.pipeline().get(HTTP2_MULTIPLEX) != null; + return channel.hasAttr(HTTP2_CONNECTION_ATTRIBUTE); } /** @@ -1096,6 +1105,7 @@ protected void initChannel(Channel ch) { pipeline.addLast(HTTP2_FRAME_CODEC, frameCodec); pipeline.addLast(HTTP2_MULTIPLEX, multiplexHandler); + pipeline.channel().attr(HTTP2_CONNECTION_ATTRIBUTE).set(Boolean.TRUE); // Attach HTTP/2 connection state for MAX_CONCURRENT_STREAMS tracking and GOAWAY draining Http2ConnectionState state = new Http2ConnectionState(); diff --git a/client/src/test/java/org/asynchttpclient/netty/channel/ChannelManagerHttp2MarkerTest.java b/client/src/test/java/org/asynchttpclient/netty/channel/ChannelManagerHttp2MarkerTest.java new file mode 100644 index 000000000..e2fc832cd --- /dev/null +++ b/client/src/test/java/org/asynchttpclient/netty/channel/ChannelManagerHttp2MarkerTest.java @@ -0,0 +1,84 @@ +/* + * Copyright (c) 2026 AsyncHttpClient Project. All rights reserved. + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.asynchttpclient.netty.channel; + +import io.netty.channel.embedded.EmbeddedChannel; +import io.netty.util.HashedWheelTimer; +import io.netty.util.Timer; +import org.junit.jupiter.api.AfterEach; +import org.junit.jupiter.api.BeforeEach; +import org.junit.jupiter.api.Test; + +import static org.asynchttpclient.Dsl.config; +import static org.junit.jupiter.api.Assertions.assertFalse; +import static org.junit.jupiter.api.Assertions.assertNotNull; +import static org.junit.jupiter.api.Assertions.assertNull; +import static org.junit.jupiter.api.Assertions.assertTrue; + +/** + * {@link ChannelManager#isHttp2(io.netty.channel.Channel)} answers from an attribute, while the thing it stands + * for is the multiplex handler in the pipeline. These pin the two together: either both say HTTP/2 or neither + * does, whichever way a later change to the upgrade sets them. + */ +class ChannelManagerHttp2MarkerTest { + + private ChannelManager channelManager; + private Timer timer; + private EmbeddedChannel channel; + + @BeforeEach + void setUp() { + timer = new HashedWheelTimer(); + channelManager = new ChannelManager(config().build(), timer); + channel = new EmbeddedChannel(); + } + + @AfterEach + void tearDown() { + channel.finishAndReleaseAll(); + timer.stop(); + } + + @Test + void aConnectionThatWasNeverUpgradedIsNotHttp2() { + assertNull(channel.pipeline().get(ChannelManager.HTTP2_MULTIPLEX), + "an untouched pipeline should not carry the multiplex handler"); + assertFalse(ChannelManager.isHttp2(channel), "and should not be reported as HTTP/2"); + } + + @Test + void upgradingAConnectionBothInstallsTheHandlerAndReportsHttp2() { + channelManager.upgradePipelineToHttp2(channel.pipeline()); + + assertNotNull(channel.pipeline().get(ChannelManager.HTTP2_MULTIPLEX), + "the upgrade should install the multiplex handler"); + assertTrue(ChannelManager.isHttp2(channel), "and should report the connection as HTTP/2"); + } + + @Test + void aStreamChannelIsNotItsParentsConnection() { + // Nothing marks a stream child, and its own pipeline carries no multiplex handler either, so the two + // agree here as well: a stream is not the connection that multiplexes it. + channelManager.upgradePipelineToHttp2(channel.pipeline()); + EmbeddedChannel stream = new EmbeddedChannel(); + try { + assertNull(stream.pipeline().get(ChannelManager.HTTP2_MULTIPLEX)); + assertFalse(ChannelManager.isHttp2(stream)); + } finally { + stream.finishAndReleaseAll(); + } + } +}