Cleanup non-retainable `Retainable`s (#9159)

`Retainable`s that return false from `canRetain()` now are noops if `retain()` is called, which allows for a simpler calling convention.
`AsyncContent` has also been reworked to allocate less and be clearer in its use of `canRetain()`.

jetty-core/jetty-client/src/main/java/org/eclipse/jetty/client/InputStreamResponseListener.java

@@ -112,8 +112,7 @@ public class InputStreamResponseListener extends Listener.Adapter
             {
                 if (LOG.isDebugEnabled())
                     LOG.debug("Queueing chunk {}", chunk);
-                if (chunk.canRetain())
+                chunk.retain();
-                    chunk.retain();
                 chunkCallbacks.add(new ChunkCallback(chunk, demander, response::abort));
                 l.signalAll();
                 return;

jetty-core/jetty-client/src/main/java/org/eclipse/jetty/client/internal/HttpReceiver.java

@@ -574,7 +574,7 @@ public abstract class HttpReceiver
                     return _chunk;
 
                 // Retain the input chunk because its ByteBuffer will be referenced by the Inflater.
-                if (retain && _chunk.canRetain())
+                if (retain)
                     _chunk.retain();
                 if (LOG.isDebugEnabled())
                     LOG.debug("decoding: {}", _chunk);

jetty-core/jetty-client/src/main/java/org/eclipse/jetty/client/internal/ResponseNotifier.java

@@ -412,8 +412,7 @@ public class ResponseNotifier
                     if (chunk.hasRemaining())
                         chunk = Content.Chunk.asChunk(chunk.getByteBuffer().slice(), chunk.isLast(), chunk);
                     // Retain the slice because it is stored for later reads.
-                    if (chunk.canRetain())
+                    chunk.retain();
-                        chunk.retain();
                     this.chunk = chunk;
                 }
                 else if (!currentChunk.isLast())

jetty-core/jetty-fcgi/jetty-fcgi-client/src/main/java/org/eclipse/jetty/fcgi/client/transport/internal/HttpReceiverOverFCGI.java

@@ -99,8 +99,7 @@ public class HttpReceiverOverFCGI extends HttpReceiver
         if (this.chunk != null)
             throw new IllegalStateException();
         // Retain the chunk because it is stored for later reads.
-        if (chunk.canRetain())
+        chunk.retain();
-            chunk.retain();
         this.chunk = chunk;
         responseContentAvailable();
     }

jetty-core/jetty-fcgi/jetty-fcgi-server/src/main/java/org/eclipse/jetty/fcgi/server/internal/HttpStreamOverFCGI.java

@@ -192,8 +192,7 @@ public class HttpStreamOverFCGI implements HttpStream
     public void onContent(Content.Chunk chunk)
     {
         // Retain the chunk because it is stored for later reads.
-        if (chunk.canRetain())
+        chunk.retain();
-            chunk.retain();
         _chunk = chunk;
     }
 

jetty-core/jetty-http/src/main/java/org/eclipse/jetty/http/MultiPartByteRanges.java

@@ -284,8 +284,7 @@ public class MultiPartByteRanges extends CompletableFuture<MultiPartByteRanges.P
         public void onPartContent(Content.Chunk chunk)
         {
             // Retain the chunk because it is stored for later use.
-            if (chunk.canRetain())
+            chunk.retain();
-                chunk.retain();
             partChunks.add(chunk);
         }
 

jetty-core/jetty-http/src/main/java/org/eclipse/jetty/http/MultiPartFormData.java

@@ -444,8 +444,7 @@ public class MultiPartFormData extends CompletableFuture<MultiPartFormData.Parts
                 }
             }
             // Retain the chunk because it is stored for later use.
-            if (chunk.canRetain())
+            chunk.retain();
-                chunk.retain();
             partChunks.add(chunk);
         }
 

jetty-core/jetty-http/src/main/java/org/eclipse/jetty/http/Trailers.java

@@ -43,22 +43,4 @@ public class Trailers implements Content.Chunk
     {
         return trailers;
     }
-
-    @Override
-    public boolean canRetain()
-    {
-        return false;
-    }
-
-    @Override
-    public void retain()
-    {
-        throw new UnsupportedOperationException();
-    }
-
-    @Override
-    public boolean release()
-    {
-        return true;
-    }
 }

jetty-core/jetty-http/src/test/java/org/eclipse/jetty/http/MultiPartTest.java

@@ -690,8 +690,7 @@ public class MultiPartTest
         public void onPartContent(Content.Chunk chunk)
         {
             // Retain the chunk because it is stored for later use.
-            if (chunk.canRetain())
+            chunk.retain();
-                chunk.retain();
             partContent.add(chunk);
         }
 

jetty-core/jetty-http2/jetty-http2-common/src/main/java/org/eclipse/jetty/http2/api/Stream.java

@@ -432,24 +432,6 @@ public interface Stream
             {
                 super(new DataFrame(streamId, BufferUtil.EMPTY_BUFFER, true));
             }
-
-            @Override
-            public boolean canRetain()
-            {
-                return false;
-            }
-
-            @Override
-            public void retain()
-            {
-                throw new UnsupportedOperationException();
-            }
-
-            @Override
-            public boolean release()
-            {
-                return true;
-            }
         }
     }
 }

jetty-core/jetty-http3/jetty-http3-common/src/main/java/org/eclipse/jetty/http3/api/Stream.java

@@ -411,24 +411,6 @@ public interface Stream
             {
                 super(new DataFrame(BufferUtil.EMPTY_BUFFER, true));
             }
-
-            @Override
-            public boolean canRetain()
-            {
-                return false;
-            }
-
-            @Override
-            public void retain()
-            {
-                throw new UnsupportedOperationException();
-            }
-
-            @Override
-            public boolean release()
-            {
-                return true;
-            }
         }
     }
 }

jetty-core/jetty-http3/jetty-http3-common/src/main/java/org/eclipse/jetty/http3/internal/HTTP3Stream.java

@@ -335,8 +335,7 @@ public abstract class HTTP3Stream implements Stream, CyclicTimeouts.Expirable, A
     public void onData(Data data)
     {
         // Retain the data because it is stored for later reads.
-        if (data.canRetain())
+        data.retain();
-            data.retain();
         if (!dataRef.compareAndSet(null, data))
             throw new IllegalStateException();
 

jetty-core/jetty-io/src/main/java/org/eclipse/jetty/io/Content.java

@@ -436,11 +436,50 @@ public class Content
         /**
          * <p>An empty, non-last, chunk.</p>
          */
-        Chunk EMPTY = ByteBufferChunk.EMPTY;
+        Chunk EMPTY = new Chunk()
+        {
+            @Override
+            public ByteBuffer getByteBuffer()
+            {
+                return BufferUtil.EMPTY_BUFFER;
+            }
+
+            @Override
+            public boolean isLast()
+            {
+                return false;
+            }
+
+            @Override
+            public String toString()
+            {
+                return "EMPTY";
+            }
+        };
+
         /**
          * <p>An empty, last, chunk.</p>
          */
-        Content.Chunk EOF = ByteBufferChunk.EOF;
+        Content.Chunk EOF = new Chunk()
+        {
+            @Override
+            public ByteBuffer getByteBuffer()
+            {
+                return BufferUtil.EMPTY_BUFFER;
+            }
+
+            @Override
+            public boolean isLast()
+            {
+                return true;
+            }
+
+            @Override
+            public String toString()
+            {
+                return "EOF";
+            }
+        };
 
         /**
          * <p>Creates a Chunk with the given ByteBuffer.</p>
@@ -657,24 +696,6 @@ public class Content
                 return true;
             }
 
-            @Override
-            public boolean canRetain()
-            {
-                return false;
-            }
-
-            @Override
-            public void retain()
-            {
-                throw new UnsupportedOperationException();
-            }
-
-            @Override
-            public boolean release()
-            {
-                return true;
-            }
-
             @Override
             public String toString()
             {

jetty-core/jetty-io/src/main/java/org/eclipse/jetty/io/Retainable.java

@@ -27,30 +27,36 @@ import java.util.concurrent.atomic.AtomicInteger;
 public interface Retainable
 {
     /**
-     * <p>Returns whether this resource can be retained, that is whether {@link #retain()}
+     * <p>Returns whether this resource is referenced counted by calls to {@link #retain()}
-     * can be called safely.</p>
+     * and {@link #release()}.</p>
-     * <p>Implementations may decide that special resources are not retainable (for example,
+     * <p>Implementations may decide that special resources are not not referenced counted (for example,
-     * {@code static} constants) so calling {@link #retain()} is not safe because it may throw.</p>
+     * {@code static} constants) so calling {@link #retain()} is a no-operation, and
-     * <p>Calling {@link #release()} on those special resources is typically allowed, and
+     * calling {@link #release()} on those special resources is a no-operation that always returns true.</p>
-     * it is a no-operation.</p>
      *
-     * @return whether it is safe to call {@link #retain()}
+     * @return true if calls to {@link #retain()} are reference counted.
      */
-    boolean canRetain();
+    default boolean canRetain()
+    {
+        return false;
+    }
 
     /**
-     * <p>Retains this resource, incrementing the reference count.</p>
+     * <p>Retains this resource, potentially incrementing a reference count if there are resources that will be released.</p>
      */
-    void retain();
+    default void retain()
+    {
+    }
 
     /**
-     * <p>Releases this resource, decrementing the reference count.</p>
+     * <p>Releases this resource, potentially decrementing a reference count (if any).</p>
-     * <p>This method returns {@code true} when the reference count goes to zero,
-     * {@code false} otherwise.</p>
      *
-     * @return whether the invocation of this method decremented the reference count to zero
+     * @return {@code true} when the reference count goes to zero or if there was no reference count,
+     *         {@code false} otherwise.
      */
-    boolean release();
+    default boolean release()
+    {
+        return true;
+    }
 
     /**
      * A wrapper of {@link Retainable} instances.

jetty-core/jetty-io/src/main/java/org/eclipse/jetty/io/content/AsyncContent.java

@@ -23,6 +23,9 @@ import java.util.Objects;
 import java.util.Queue;
 
 import org.eclipse.jetty.io.Content;
+import org.eclipse.jetty.io.Retainable;
+import org.eclipse.jetty.io.internal.ByteBufferChunk;
+import org.eclipse.jetty.util.BufferUtil;
 import org.eclipse.jetty.util.Callback;
 import org.eclipse.jetty.util.thread.AutoLock;
 import org.eclipse.jetty.util.thread.SerializedInvoker;
@@ -37,10 +40,18 @@ import org.eclipse.jetty.util.thread.SerializedInvoker;
 public class AsyncContent implements Content.Sink, Content.Source, Closeable
 {
     private static final int UNDETERMINED_LENGTH = -2;
+    private static final AsyncChunk ASYNC_EOF = new AsyncChunk(true, BufferUtil.EMPTY_BUFFER, Callback.NOOP)
+    {
+        @Override
+        public String toString()
+        {
+            return "ASYNC_EOF";
+        }
+    };
 
     private final AutoLock.WithCondition lock = new AutoLock.WithCondition();
     private final SerializedInvoker invoker = new SerializedInvoker();
-    private final Queue<ChunkCallback> chunks = new ArrayDeque<>();
+    private final Queue<AsyncChunk> chunks = new ArrayDeque<>();
     private Content.Chunk.Error errorChunk;
     private boolean readClosed;
     private boolean writeClosed;
@@ -52,20 +63,15 @@ public class AsyncContent implements Content.Sink, Content.Source, Closeable
      * <p>The write completes:</p>
      * <ul>
      * <li>immediately with a failure when this instance is closed or already in error</li>
-     * <li>successfully when the {@link Content.Chunk} returned by {@link #read()} is released</li>
+     * <li>successfully when a non empty {@link Content.Chunk} returned by {@link #read()} is released</li>
      * <li>successfully just before the {@link Content.Chunk} is returned by {@link #read()},
-     * if the chunk {@link Content.Chunk#canRetain() cannot be retained}</li>
+     * for any empty chunk {@link Content.Chunk}.</li>
      * </ul>
      */
     @Override
     public void write(boolean last, ByteBuffer byteBuffer, Callback callback)
     {
-        Content.Chunk chunk;
+        offer(new AsyncChunk(last, byteBuffer, callback));
-        if (byteBuffer.hasRemaining())
-            chunk = Content.Chunk.from(byteBuffer, last, callback::succeeded);
-        else
-            chunk = last ? Content.Chunk.EOF : Content.Chunk.EMPTY;
-        offer(chunk, callback);
     }
 
     /**
@@ -73,14 +79,8 @@ public class AsyncContent implements Content.Sink, Content.Source, Closeable
      * or succeeded if and only if the chunk is terminal, as non-terminal
      * chunks have to bind the succeeding of the callback to their release.
      */
-    private void offer(Content.Chunk chunk, Callback callback)
+    private void offer(AsyncChunk chunk)
     {
-        if (chunk instanceof Content.Chunk.Error)
-        {
-            callback.failed(new IllegalArgumentException("Cannot not write Chunk.Error instances, call fail(Throwable) instead"));
-            return;
-        }
-
         Throwable failure = null;
         boolean wasEmpty = false;
         try (AutoLock ignored = lock.lock())
@@ -98,17 +98,21 @@ public class AsyncContent implements Content.Sink, Content.Source, Closeable
                 wasEmpty = chunks.isEmpty();
                 // No need to retain the chunk, because it's created internally
                 // from a ByteBuffer and it will be released by the caller of read().
-                chunks.offer(new ChunkCallback(chunk, callback));
+                chunks.offer(chunk);
                 if (chunk.isLast())
                 {
                     writeClosed = true;
                     if (length == UNDETERMINED_LENGTH)
-                        length = chunks.stream().mapToLong(cc -> cc.chunk().remaining()).sum();
+                    {
+                        length = 0;
+                        for (AsyncChunk c : chunks)
+                            length += c.remaining();
+                    }
                 }
             }
         }
         if (failure != null)
-            callback.failed(failure);
+            chunk.failed(failure);
         if (wasEmpty)
             invoker.run(this::invokeDemandCallback);
     }
@@ -128,7 +132,7 @@ public class AsyncContent implements Content.Sink, Content.Source, Closeable
                 // Special case for a last empty chunk that may not be read.
                 if (writeClosed && chunks.size() == 1)
                 {
-                    Content.Chunk chunk = chunks.peek().chunk();
+                    AsyncChunk chunk = chunks.peek();
                     if (chunk.isLast() && !chunk.hasRemaining())
                         return;
                 }
@@ -144,7 +148,7 @@ public class AsyncContent implements Content.Sink, Content.Source, Closeable
     @Override
     public void close()
     {
-        offer(Content.Chunk.EOF, Callback.NOOP);
+        offer(ASYNC_EOF);
     }
 
     public boolean isClosed()
@@ -167,7 +171,7 @@ public class AsyncContent implements Content.Sink, Content.Source, Closeable
     @Override
     public Content.Chunk read()
     {
-        ChunkCallback current;
+        AsyncChunk current;
         try (AutoLock.WithCondition condition = lock.lock())
         {
             if (length == UNDETERMINED_LENGTH)
@@ -181,13 +185,18 @@ public class AsyncContent implements Content.Sink, Content.Source, Closeable
                     return errorChunk;
                 return null;
             }
-            readClosed = current.chunk().isLast();
+            readClosed = current.isLast();
             if (chunks.isEmpty())
                 condition.signal();
         }
-        if (!current.chunk().canRetain())
+
-            current.callback().succeeded();
+        // If the chunk is reference counted, the callback is succeeded when it is released.
-        return current.chunk();
+        if (current.canRetain())
+            return current;
+
+        // If the chunk is not reference counted, we can succeed it now and return a chunk with a noop release.
+        current.succeeded();
+        return current.isLast() ? Content.Chunk.EOF : Content.Chunk.EMPTY;
     }
 
     @Override
@@ -232,7 +241,7 @@ public class AsyncContent implements Content.Sink, Content.Source, Closeable
     @Override
     public void fail(Throwable failure)
     {
-        List<ChunkCallback> drained;
+        List<AsyncChunk> drained;
         try (AutoLock.WithCondition condition = lock.lock())
         {
             if (readClosed)
@@ -244,7 +253,7 @@ public class AsyncContent implements Content.Sink, Content.Source, Closeable
             chunks.clear();
             condition.signal();
         }
-        drained.forEach(cc -> cc.callback().failed(failure));
+        drained.forEach(ac -> ac.failed(failure));
         invoker.run(this::invokeDemandCallback);
     }
 
@@ -256,7 +265,52 @@ public class AsyncContent implements Content.Sink, Content.Source, Closeable
         }
     }
 
-    private record ChunkCallback(Content.Chunk chunk, Callback callback)
+    private static class AsyncChunk extends ByteBufferChunk implements Callback
     {
+        private final Callback callback;
+        private final Retainable.ReferenceCounter referenceCounter;
+
+        public AsyncChunk(boolean last, ByteBuffer byteBuffer, Callback callback)
+        {
+            super(byteBuffer.hasRemaining() ? byteBuffer : BufferUtil.EMPTY_BUFFER, last);
+            this.callback = callback;
+            referenceCounter = getByteBuffer() == BufferUtil.EMPTY_BUFFER ? null : new ReferenceCounter();
+        }
+
+        @Override
+        public boolean canRetain()
+        {
+            return referenceCounter != null;
+        }
+
+        @Override
+        public void retain()
+        {
+            if (canRetain())
+                referenceCounter.retain();
+        }
+
+        @Override
+        public boolean release()
+        {
+            if (!canRetain())
+                return true;
+            boolean released = referenceCounter.release();
+            if (released)
+                succeeded();
+            return released;
+        }
+
+        @Override
+        public void succeeded()
+        {
+            callback.succeeded();
+        }
+
+        @Override
+        public void failed(Throwable x)
+        {
+            callback.failed(x);
+        }
     }
 }

jetty-core/jetty-io/src/main/java/org/eclipse/jetty/io/content/ContentSinkSubscriber.java

@@ -48,8 +48,7 @@ public class ContentSinkSubscriber implements Flow.Subscriber<Content.Chunk>
     public void onNext(Content.Chunk chunk)
     {
         // Retain the chunk because the write may not complete immediately.
-        if (chunk.canRetain())
+        chunk.retain();
-            chunk.retain();
         sink.write(chunk.isLast(), chunk.getByteBuffer(), Callback.from(() -> succeeded(chunk), x -> failed(chunk, x)));
     }
 

jetty-core/jetty-io/src/main/java/org/eclipse/jetty/io/internal/ByteBufferChunk.java

@@ -24,23 +24,6 @@ import org.eclipse.jetty.util.BufferUtil;
 
 public abstract class ByteBufferChunk implements Content.Chunk
 {
-    public static final ByteBufferChunk EMPTY = new ByteBufferChunk(BufferUtil.EMPTY_BUFFER, false)
-    {
-        @Override
-        public String toString()
-        {
-            return "%s[EMPTY]".formatted(ByteBufferChunk.class.getSimpleName());
-        }
-    };
-    public static final ByteBufferChunk EOF = new ByteBufferChunk(BufferUtil.EMPTY_BUFFER, true)
-    {
-        @Override
-        public String toString()
-        {
-            return "%s[EOF]".formatted(ByteBufferChunk.class.getSimpleName());
-        }
-    };
-
     private final ByteBuffer byteBuffer;
     private final boolean last;
 
@@ -62,24 +45,6 @@ public abstract class ByteBufferChunk implements Content.Chunk
         return last;
     }
 
-    @Override
-    public boolean canRetain()
-    {
-        return false;
-    }
-
-    @Override
-    public void retain()
-    {
-        throw new UnsupportedOperationException();
-    }
-
-    @Override
-    public boolean release()
-    {
-        return true;
-    }
-
     @Override
     public String toString()
     {

jetty-core/jetty-io/src/test/java/org/eclipse/jetty/io/ContentSourceTest.java

@@ -525,8 +525,7 @@ public class ContentSourceTest
         private void add(Content.Chunk chunk)
         {
             // Retain the chunk because it is stored for later use.
-            if (chunk.canRetain())
+            chunk.retain();
-                chunk.retain();
             _chunks.add(chunk);
         }
 

jetty-core/jetty-proxy/src/main/java/org/eclipse/jetty/proxy/ProxyHandler.java

@@ -688,8 +688,7 @@ public abstract class ProxyHandler extends Handler.Abstract
             if (LOG.isDebugEnabled())
                 LOG.debug("{} S2P received content {}", requestId(clientToProxyRequest), BufferUtil.toDetailString(serverToProxyContent));
 
-            if (serverToProxyChunk.canRetain())
+            serverToProxyChunk.retain();
-                serverToProxyChunk.retain();
             Callback callback = new Callback()
             {
                 @Override

jetty-core/jetty-server/src/main/java/org/eclipse/jetty/server/handler/gzip/GzipRequest.java

@@ -165,7 +165,7 @@ public class GzipRequest extends Request.Wrapper
                 return Content.Chunk.EOF;
 
             // Retain the input chunk because its ByteBuffer will be referenced by the Inflater.
-            if (retain && _chunk.canRetain())
+            if (retain)
                 _chunk.retain();
             ByteBuffer decodedBuffer = _decoder.decode(_chunk);
 

jetty-core/jetty-server/src/test/java/org/eclipse/jetty/server/MockHttpStream.java

@@ -46,24 +46,6 @@ public class MockHttpStream implements HttpStream
         {
             return false;
         }
-
-        @Override
-        public boolean canRetain()
-        {
-            return false;
-        }
-
-        @Override
-        public void retain()
-        {
-            throw new UnsupportedOperationException();
-        }
-
-        @Override
-        public boolean release()
-        {
-            return true;
-        }
     };
     private final long _nanoTime = NanoTime.now();
     private final AtomicReference<Content.Chunk> _content = new AtomicReference<>();
@@ -106,8 +88,7 @@ public class MockHttpStream implements HttpStream
 
     private Runnable addContent(Content.Chunk chunk)
     {
-        if (chunk.canRetain())
+        chunk.retain();
-            chunk.retain();
         chunk = _content.getAndSet(chunk);
         if (chunk == DEMAND)
             return _channel.onContentAvailable();

jetty-core/jetty-tests/jetty-test-client-transports/src/test/java/org/eclipse/jetty/test/client/transport/HttpClientDemandTest.java

@@ -154,8 +154,7 @@ public class HttpClientDemandTest extends AbstractTest
                 public void onContent(Response response, Content.Chunk chunk, Runnable demander)
                 {
                     // Store the chunk and don't demand.
-                    if (chunk.canRetain())
+                    chunk.retain();
-                        chunk.retain();
                     contentQueue.offer(chunk);
                     demanderQueue.offer(demander);
                 }
@@ -244,8 +243,7 @@ public class HttpClientDemandTest extends AbstractTest
         client.newRequest(newURI(transport))
             .onResponseContentAsync((response, chunk, demander) ->
             {
-                if (chunk.canRetain())
+                chunk.retain();
-                    chunk.retain();
                 chunkRef.set(chunk);
                 try
                 {

jetty-ee10/jetty-ee10-proxy/src/main/java/org/eclipse/jetty/ee10/proxy/AsyncMiddleManServlet.java

@@ -439,8 +439,7 @@ public class AsyncMiddleManServlet extends AbstractProxyServlet
         @Override
         public void onContent(Response serverResponse, Content.Chunk chunk, Runnable demander)
         {
-            if (chunk.canRetain())
+            chunk.retain();
-                chunk.retain();
             Callback callback = Callback.from(chunk::release, Callback.from(demander, serverResponse::abort));
             try
             {

jetty-ee10/jetty-ee10-proxy/src/main/java/org/eclipse/jetty/ee10/proxy/ProxyServlet.java

@@ -216,8 +216,7 @@ public class ProxyServlet extends AbstractProxyServlet
                 content.get(buffer);
                 offset = 0;
             }
-            if (chunk.canRetain())
+            chunk.retain();
-                chunk.retain();
             Callback callback = Callback.from(chunk::release, Callback.from(demander, proxyResponse::abort));
             onResponseContent(request, response, proxyResponse, buffer, offset, length, callback);
         }

jetty-ee9/jetty-ee9-proxy/src/main/java/org/eclipse/jetty/ee9/proxy/AsyncMiddleManServlet.java

@@ -439,8 +439,7 @@ public class AsyncMiddleManServlet extends AbstractProxyServlet
         @Override
         public void onContent(Response serverResponse, Content.Chunk chunk, Runnable demander)
         {
-            if (chunk.canRetain())
+            chunk.retain();
-                chunk.retain();
             Callback callback = Callback.from(chunk::release, Callback.from(demander, serverResponse::abort));
             try
             {

jetty-ee9/jetty-ee9-proxy/src/main/java/org/eclipse/jetty/ee9/proxy/ProxyServlet.java

@@ -216,8 +216,7 @@ public class ProxyServlet extends AbstractProxyServlet
                 content.get(buffer);
                 offset = 0;
             }
-            if (chunk.canRetain())
+            chunk.retain();
-                chunk.retain();
             Callback callback = Callback.from(chunk::release, Callback.from(demander, proxyResponse::abort));
             onResponseContent(request, response, proxyResponse, buffer, offset, length, callback);
         }