commit a37d3eb349e048b953633027ed011cda8b68c603
Author: George Gensure <werkt0@gmail.com>
Date:   Thu Jul 10 09:49:54 2025 -0400

    Guarantee missing stream promise delivery
    
    In observed cases, whether RST_STREAM or another failure from netty or
    the server, listeners can fail to be notified when a connection yields a
    null stream for the selected streamId. This causes hangs in clients,
    despite deadlines, with no obvious resolution.
    
    Tests which relied upon this promise succeeding must now change.

diff --git a/netty/src/main/java/io/grpc/netty/NettyClientHandler.java b/netty/src/main/java/io/grpc/netty/NettyClientHandler.java
index a5fa0f800..276fa623c 100644
--- a/netty/src/main/java/io/grpc/netty/NettyClientHandler.java
+++ b/netty/src/main/java/io/grpc/netty/NettyClientHandler.java
@@ -738,14 +738,19 @@ class NettyClientHandler extends AbstractNettyHandler {
 
                 // Attach the client stream to the HTTP/2 stream object as user data.
                 stream.setHttp2Stream(http2Stream);
+                promise.setSuccess();
+              } else {
+                // Otherwise, the stream has been cancelled and Netty is sending a
+                // RST_STREAM frame which causes it to purge pending writes from the
+                // flow-controller and delete the http2Stream. The stream listener has already
+                // been notified of cancellation so there is nothing to do.
+                //
+                // This process has been observed to fail in some circumstances, leaving listeners
+                // unanswered. Ensure that some exception has been delivered consistent with the
+                // implied RST_STREAM result above.
+                Status status = Status.INTERNAL.withDescription("unknown stream for connection");
+                promise.setFailure(status.asRuntimeException());
               }
-              // Otherwise, the stream has been cancelled and Netty is sending a
-              // RST_STREAM frame which causes it to purge pending writes from the
-              // flow-controller and delete the http2Stream. The stream listener has already
-              // been notified of cancellation so there is nothing to do.
-
-              // Just forward on the success status to the original promise.
-              promise.setSuccess();
             } else {
               Throwable cause = future.cause();
               if (cause instanceof StreamBufferingEncoder.Http2GoAwayException) {
diff --git a/netty/src/test/java/io/grpc/netty/NettyClientHandlerTest.java b/netty/src/test/java/io/grpc/netty/NettyClientHandlerTest.java
index f8fbeea9b..dd4fcb4ea 100644
--- a/netty/src/test/java/io/grpc/netty/NettyClientHandlerTest.java
+++ b/netty/src/test/java/io/grpc/netty/NettyClientHandlerTest.java
@@ -268,7 +268,7 @@ public class NettyClientHandlerTest extends NettyHandlerTestBase<NettyClientHand
     // Cancel the stream.
     cancelStream(Status.CANCELLED);
 
-    assertTrue(createFuture.isSuccess());
+    assertFalse(createFuture.isSuccess());
     verify(streamListener).closed(eq(Status.CANCELLED), same(PROCESSED), any(Metadata.class));
   }
 
@@ -311,7 +311,7 @@ public class NettyClientHandlerTest extends NettyHandlerTestBase<NettyClientHand
     ChannelFuture cancelFuture = cancelStream(Status.CANCELLED);
     assertTrue(cancelFuture.isSuccess());
     assertTrue(createFuture.isDone());
-    assertTrue(createFuture.isSuccess());
+    assertFalse(createFuture.isSuccess());
   }
 
   /**