Avoid using JVM HashCode on Http 2 DefaultStream (#13760)

franz1981 · web-flow · commit 4dea3f7cf525 · 2024-01-12T12:12:06.000+01:00
Motivation:

relying on DefaultStream's hashCode forces calling into JVM's strategy
for identity hash code

Modifications:

Use the stream's id to identify DefaultStream

Result:

Faster active stream insertion, saving producing JVM's hashcode
diff --git a/codec-http2/src/main/java/io/netty/handler/codec/http2/DefaultHttp2Connection.java b/codec-http2/src/main/java/io/netty/handler/codec/http2/DefaultHttp2Connection.java
@@ -388,11 +388,13 @@ private class DefaultStream implements Http2Stream {
         private static final byte META_STATE_RECV_HEADERS = 1 << 4;
         private static final byte META_STATE_RECV_TRAILERS = 1 << 5;
         private final int id;
+        private final long identity;
         private final PropertyMap properties = new PropertyMap();
         private State state;
         private byte metaState;
 
-        DefaultStream(int id, State state) {
+        DefaultStream(long identity, int id, State state) {
+            this.identity = identity;
             this.id = id;
             this.state = state;
         }
@@ -599,14 +601,28 @@ void resizeIfNecessary(int index) {
                 }
             }
         }
+
+        @Override
+        public boolean equals(final Object obj) {
+            return super.equals(obj);
+        }
+
+        @Override
+        public int hashCode() {
+            long value = identity;
+            if (value == 0) {
+                return System.identityHashCode(this);
+            }
+            return (int) (value ^ (value >>> 32));
+        }
     }
 
     /**
      * Stream class representing the connection, itself.
      */
     private final class ConnectionStream extends DefaultStream {
         ConnectionStream() {
-            super(CONNECTION_STREAM_ID, IDLE);
+            super(0, CONNECTION_STREAM_ID, IDLE);
         }
 
         @Override
@@ -670,6 +686,10 @@ public boolean isPushPromiseSent() {
      */
     private final class DefaultEndpoint<F extends Http2FlowController> implements Endpoint<F> {
         private final boolean server;
+        /**
+         * This is an always increasing sequence number used to hash {@link DefaultStream} instances.
+         */
+        private long lastCreatedStreamIdentity;
         /**
          * The minimum stream ID allowed when creating the next stream. This only applies at the time the stream is
          * created. If the ID of the stream being created is less than this value, stream creation will fail. Upon
@@ -694,6 +714,7 @@ private final class DefaultEndpoint<F extends Http2FlowController> implements En
         int numStreams;
 
         DefaultEndpoint(boolean server, int maxReservedStreams) {
+            this.lastCreatedStreamIdentity = 0;
             this.server = server;
 
             // Determine the starting stream ID for this endpoint. Client-initiated streams
@@ -750,8 +771,10 @@ public DefaultStream createStream(int streamId, boolean halfClosed) throws Http2
 
             checkNewStreamAllowed(streamId, state);
 
+            lastCreatedStreamIdentity++;
+
             // Create and initialize the stream.
-            DefaultStream stream = new DefaultStream(streamId, state);
+            DefaultStream stream = new DefaultStream(lastCreatedStreamIdentity, streamId, state);
 
             incrementExpectedStreamId(streamId);
 
@@ -785,8 +808,10 @@ public DefaultStream reservePushStream(int streamId, Http2Stream parent) throws
             State state = isLocal() ? RESERVED_LOCAL : RESERVED_REMOTE;
             checkNewStreamAllowed(streamId, state);
 
+            lastCreatedStreamIdentity++;
+
             // Create and initialize the stream.
-            DefaultStream stream = new DefaultStream(streamId, state);
+            DefaultStream stream = new DefaultStream(lastCreatedStreamIdentity, streamId, state);
 
             incrementExpectedStreamId(streamId);
 
