Fix HTTP/2 stream semaphore leak

client/src/main/java/org/asynchttpclient/netty/channel/Http2ConnectionState.java

@@ -35,6 +35,7 @@ public class Http2ConnectionState {
     private final AtomicBoolean draining = new AtomicBoolean(false);
     private volatile int lastGoAwayStreamId = Integer.MAX_VALUE;
     private final ConcurrentLinkedQueue<Runnable> pendingOpeners = new ConcurrentLinkedQueue<>();
+    private final Object pendingLock = new Object();
     private volatile Object partitionKey;
 
     public boolean tryAcquireStream() {
@@ -54,22 +55,29 @@ public boolean tryAcquireStream() {
 
     public void releaseStream() {
         activeStreams.decrementAndGet();
-        // Try to dequeue and run a pending opener
-        Runnable pending = pendingOpeners.poll();
-        if (pending != null) {
-            pending.run();
-        }
+        drainPendingOpeners();
     }
 
     public void addPendingOpener(Runnable opener) {
-        pendingOpeners.add(opener);
-        // Re-check in case a stream was released between the failed tryAcquire and this enqueue
-        if (tryAcquireStream()) {
-            Runnable dequeued = pendingOpeners.poll();
-            if (dequeued != null) {
-                dequeued.run();
+        synchronized (pendingLock) {
+            if (tryAcquireStream()) {
+                opener.run();
             } else {
-                releaseStream();
+                pendingOpeners.add(opener);
+            }
+        }
+    }
+
+    private void drainPendingOpeners() {
+        synchronized (pendingLock) {
+            Runnable pending = pendingOpeners.poll();
+            if (pending != null) {
+                if (tryAcquireStream()) {
+                    pending.run();
+                } else {
+                    // Put it back — another releaseStream() will pick it up
+                    pendingOpeners.offer(pending);
+                }
             }
         }
     }

client/src/main/java/org/asynchttpclient/netty/handler/Http2Handler.java

@@ -302,9 +302,16 @@ private void readFailed(Channel channel, NettyResponseFuture<?> future, Throwabl
 
     @Override
     public void handleException(NettyResponseFuture<?> future, Throwable error) {
+        if (!future.isDone()) {
+            readFailed(future.channel(), future, error);
+        }
     }
 
     @Override
     public void handleChannelInactive(NettyResponseFuture<?> future) {
+        if (!future.isDone()) {
+            readFailed(future.channel(), future,
+                    new IOException("HTTP/2 stream channel closed unexpectedly"));
+        }
     }
 }

client/src/main/java/org/asynchttpclient/netty/request/NettyRequestSender.java

@@ -276,8 +276,12 @@ private <T> ListenableFuture<T> sendRequestWithOpenChannel(NettyResponseFuture<T
 
         // channelInactive might be called between isChannelValid and writeRequest
         // so if we don't store the Future now, channelInactive won't perform
-        // handleUnexpectedClosedChannel
-        Channels.setAttribute(channel, future);
+        // handleUnexpectedClosedChannel.
+        // For HTTP/2 parent channels, skip this — each stream channel gets its own attribute
+        // in openHttp2Stream(), and setting it on the parent would corrupt multiplexed state.
+        if (!ChannelManager.isHttp2(channel)) {
+            Channels.setAttribute(channel, future);
+        }
 
         if (Channels.isChannelActive(channel)) {
             writeRequest(future, channel);
@@ -485,7 +489,6 @@ public <T> void writeRequest(NettyResponseFuture<T> future, Channel channel) {
      */
     private <T> void writeHttp2Request(NettyResponseFuture<T> future, Channel parentChannel) {
         Http2ConnectionState state = parentChannel.attr(Http2ConnectionState.HTTP2_STATE_KEY).get();
-        Runnable openStream = () -> openHttp2Stream(future, parentChannel);
 
         if (state != null && !state.tryAcquireStream()) {
             if (state.isDraining()) {
@@ -495,13 +498,13 @@ private <T> void writeHttp2Request(NettyResponseFuture<T> future, Channel parent
                 return;
             }
             // Queue for later when a stream slot opens up
-            state.addPendingOpener(openStream);
+            state.addPendingOpener(() -> openHttp2Stream(future, parentChannel, state));
             return;
         }
-        openStream.run();
+        openHttp2Stream(future, parentChannel, state);
     }
 
-    private <T> void openHttp2Stream(NettyResponseFuture<T> future, Channel parentChannel) {
+    private <T> void openHttp2Stream(NettyResponseFuture<T> future, Channel parentChannel, Http2ConnectionState state) {
         new Http2StreamChannelBootstrap(parentChannel)
                 .handler(new ChannelInitializer<Http2StreamChannel>() {
                     @Override
@@ -519,6 +522,7 @@ protected void initChannel(Http2StreamChannel streamCh) {
                         Http2StreamChannel streamChannel = f.getNow();
                         channelManager.registerOpenChannel(streamChannel);
                         Channels.setAttribute(streamChannel, future);
+                        Channels.setActiveToken(streamChannel);
                         future.attachChannel(streamChannel, false);
                         try {
                             AsyncHandler<T> asyncHandler = future.getAsyncHandler();
@@ -541,6 +545,10 @@ protected void initChannel(Http2StreamChannel streamCh) {
                             abort(streamChannel, future, e);
                         }
                     } else {
+                        // Stream channel was never opened — release the acquired stream slot
+                        if (state != null) {
+                            state.releaseStream();
+                        }
                         abort(parentChannel, future, f.cause());
                     }
                 });