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Avoid per-connect lock on shared Bootstrap options map (#2218) #2219

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Avoid per-connect lock on shared Bootstrap options map (#2218) #2219

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24be64d
Avoid per-connect lock on shared Bootstrap options map (#2218)
pavel-ptashyts Jun 30, 2026
fab425c
Avoid per-connect lock on shared Bootstrap options map (#2218)
pavel-ptashyts Jun 30, 2026
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71 changes: 54 additions & 17 deletions client/src/main/java/org/asynchttpclient/netty/channel/ChannelManager.java
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@
import io.netty.bootstrap.Bootstrap;
import io.netty.buffer.ByteBufAllocator;
import io.netty.channel.Channel;
import io.netty.channel.ChannelConfig;
import io.netty.channel.ChannelFactory;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
Expand Down Expand Up @@ -93,6 +94,7 @@
import java.io.IOException;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.concurrent.ConcurrentHashMap;
Expand Down Expand Up @@ -129,6 +131,9 @@ public class ChannelManager {
private final boolean allowReleaseEventLoopGroup;
private final Bootstrap httpBootstrap;
private final Bootstrap wsBootstrap;
// Channel options, resolved from config once at construction, applied to each channel from the channel
// initializer instead of via Bootstrap#option to avoid Netty's synchronized per-connect options map (issue #2218).
private final Map.Entry<ChannelOption<?>, Object>[] channelOptions;
private final long handshakeTimeout;
private final @Nullable AddressResolverGroup<InetSocketAddress> addressResolverGroup;

Expand Down Expand Up @@ -200,8 +205,9 @@ public ChannelManager(final AsyncHttpClientConfig config, Timer nettyTimer) {
}
}

httpBootstrap = newBootstrap(transportFactory, eventLoopGroup, config);
wsBootstrap = newBootstrap(transportFactory, eventLoopGroup, config);
channelOptions = buildChannelOptions(config);
httpBootstrap = newBootstrap(transportFactory, eventLoopGroup);
wsBootstrap = newBootstrap(transportFactory, eventLoopGroup);

// Use the address resolver group from config if provided; otherwise null (legacy per-request resolution)
addressResolverGroup = config.getAddressResolverGroup();
Expand Down Expand Up @@ -243,37 +249,64 @@ public static boolean isSslHandlerConfigured(ChannelPipeline pipeline) {
return pipeline.get(SSL_HANDLER) != null;
}

private static Bootstrap newBootstrap(ChannelFactory<? extends Channel> channelFactory, EventLoopGroup eventLoopGroup, AsyncHttpClientConfig config) {
Bootstrap bootstrap = new Bootstrap().channelFactory(channelFactory).group(eventLoopGroup)
.option(ChannelOption.ALLOCATOR, config.getAllocator() != null ? config.getAllocator() : ByteBufAllocator.DEFAULT)
.option(ChannelOption.TCP_NODELAY, config.isTcpNoDelay())
.option(ChannelOption.SO_REUSEADDR, config.isSoReuseAddress())
.option(ChannelOption.SO_KEEPALIVE, config.isSoKeepAlive())
.option(ChannelOption.AUTO_CLOSE, false);
private static Bootstrap newBootstrap(ChannelFactory<? extends Channel> channelFactory, EventLoopGroup eventLoopGroup) {
// Channel options are intentionally NOT set on the Bootstrap. Netty's AbstractBootstrap applies them
// per-connect by copying the shared options map under "synchronized (options)" in newOptionsArray(),
// which serializes every outbound connection on a single monitor (issue #2218). Instead, we apply the
// pre-resolved options to each Channel from the channel initializer via Channel.config(), keeping the
// Bootstrap options map empty and removing that global lock from the connect path.
return new Bootstrap().channelFactory(channelFactory).group(eventLoopGroup);
}

/**
* Resolves the configured {@link ChannelOption}s from the client config exactly once. Values and conditional
* options (connect timeout, SO_LINGER, buffer sizes) are computed here so the per-connection path only iterates
* a fixed array and never re-reads the config.
*/
@SuppressWarnings("unchecked")
private static Map.Entry<ChannelOption<?>, Object>[] buildChannelOptions(AsyncHttpClientConfig config) {
Map<ChannelOption<?>, Object> options = new LinkedHashMap<>();
options.put(ChannelOption.ALLOCATOR, config.getAllocator() != null ? config.getAllocator() : ByteBufAllocator.DEFAULT);
options.put(ChannelOption.TCP_NODELAY, config.isTcpNoDelay());
options.put(ChannelOption.SO_REUSEADDR, config.isSoReuseAddress());
options.put(ChannelOption.SO_KEEPALIVE, config.isSoKeepAlive());
options.put(ChannelOption.AUTO_CLOSE, false);

long connectTimeout = config.getConnectTimeout().toMillis();
if (connectTimeout > 0) {
connectTimeout = Math.min(connectTimeout, Integer.MAX_VALUE);
bootstrap.option(ChannelOption.CONNECT_TIMEOUT_MILLIS, (int) connectTimeout);
options.put(ChannelOption.CONNECT_TIMEOUT_MILLIS, (int) connectTimeout);
}

if (config.getSoLinger() >= 0) {
bootstrap.option(ChannelOption.SO_LINGER, config.getSoLinger());
options.put(ChannelOption.SO_LINGER, config.getSoLinger());
}

if (config.getSoSndBuf() >= 0) {
bootstrap.option(ChannelOption.SO_SNDBUF, config.getSoSndBuf());
options.put(ChannelOption.SO_SNDBUF, config.getSoSndBuf());
}

if (config.getSoRcvBuf() >= 0) {
bootstrap.option(ChannelOption.SO_RCVBUF, config.getSoRcvBuf());
options.put(ChannelOption.SO_RCVBUF, config.getSoRcvBuf());
}

for (Entry<ChannelOption<Object>, Object> entry : config.getChannelOptions().entrySet()) {
bootstrap.option(entry.getKey(), entry.getValue());
}
// User-supplied options last so they can override the defaults above, matching the previous Bootstrap order.
options.putAll(config.getChannelOptions());

return options.entrySet().toArray(new Map.Entry[0]);
}

return bootstrap;
/**
* Applies the pre-resolved channel options to a freshly created channel. Invoked from the channel initializer
* (once per connection, on the channel's event loop, before the channel is connected), mirroring what
* {@link Bootstrap#option} would otherwise do but without the shared, synchronized options map.
*/
@SuppressWarnings("unchecked")
private void applyChannelOptions(Channel channel) {
ChannelConfig channelConfig = channel.config();
for (Map.Entry<ChannelOption<?>, Object> option : channelOptions) {
channelConfig.setOption((ChannelOption<Object>) option.getKey(), option.getValue());
}
}

public void configureBootstraps(NettyRequestSender requestSender) {
Expand All @@ -284,6 +317,8 @@ public void configureBootstraps(NettyRequestSender requestSender) {
httpBootstrap.handler(new ChannelInitializer<Channel>() {
@Override
protected void initChannel(Channel ch) {
applyChannelOptions(ch);

ChannelPipeline pipeline = ch.pipeline()
.addLast(HTTP_CLIENT_CODEC, newHttpClientCodec());

Expand All @@ -309,6 +344,8 @@ protected void initChannel(Channel ch) {
wsBootstrap.handler(new ChannelInitializer<Channel>() {
@Override
protected void initChannel(Channel ch) {
applyChannelOptions(ch);

ChannelPipeline pipeline = ch.pipeline()
.addLast(HTTP_CLIENT_CODEC, newHttpClientCodec())
.addLast(AHC_WS_HANDLER, wsHandler);
Expand Down
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