Remove netty BytesReference implementations (#54355)

Elasticsearch has a number of different BytesReference implementations.
These implementations can all implement the interface in different ways
with subtly different behavior and performance characteristics. On the
other-hand, the JVM only represents bytes as an array or a direct byte
buffer. This commit deletes the specialized Netty implementations and
moves to using a generic ByteBuffer reference type. This will allow us
to focus on standardizing performance and behave around a smaller number
of implementations that can be used by all components in Elasticsearch.

Author: Tim-Brooks

modules/transport-netty4/src/main/java/org/elasticsearch/transport/netty4/ByteBufBytesReference.java

@@ -30,6 +30,7 @@
 import org.elasticsearch.common.bytes.BytesReference;
 
 import java.io.IOException;
+import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Locale;
@@ -80,28 +81,24 @@ public static ByteBuf toByteBuf(final BytesReference reference) {
         if (reference.length() == 0) {
             return Unpooled.EMPTY_BUFFER;
         }
-        if (reference instanceof ByteBufBytesReference) {
-            return ((ByteBufBytesReference) reference).toByteBuf();
-        } else {
-            final BytesRefIterator iterator = reference.iterator();
-            // usually we have one, two, or three components from the header, the message, and a buffer
-            final List<ByteBuf> buffers = new ArrayList<>(3);
-            try {
-                BytesRef slice;
-                while ((slice = iterator.next()) != null) {
-                    buffers.add(Unpooled.wrappedBuffer(slice.bytes, slice.offset, slice.length));
-                }
+        final BytesRefIterator iterator = reference.iterator();
+        // usually we have one, two, or three components from the header, the message, and a buffer
+        final List<ByteBuf> buffers = new ArrayList<>(3);
+        try {
+            BytesRef slice;
+            while ((slice = iterator.next()) != null) {
+                buffers.add(Unpooled.wrappedBuffer(slice.bytes, slice.offset, slice.length));
+            }
 
-                if (buffers.size() == 1) {
-                    return buffers.get(0);
-                } else {
-                    CompositeByteBuf composite = Unpooled.compositeBuffer(buffers.size());
-                    composite.addComponents(true, buffers);
-                    return composite;
-                }
-            } catch (IOException ex) {
-                throw new AssertionError("no IO happens here", ex);
+            if (buffers.size() == 1) {
+                return buffers.get(0);
+            } else {
+                CompositeByteBuf composite = Unpooled.compositeBuffer(buffers.size());
+                composite.addComponents(true, buffers);
+                return composite;
             }
+        } catch (IOException ex) {
+            throw new AssertionError("no IO happens here", ex);
         }
     }
 
@@ -112,7 +109,9 @@ public static BytesReference toBytesReference(final ByteBuf buffer) {
         final int readableBytes = buffer.readableBytes();
         if (readableBytes == 0) {
             return BytesArray.EMPTY;
+        } else {
+            final ByteBuffer[] byteBuffers = buffer.nioBuffers();
+            return BytesReference.fromByteBuffers(byteBuffers);
         }
-        return new ByteBufBytesReference(buffer, buffer.readableBytes());
     }
 }

modules/transport-netty4/src/main/java/org/elasticsearch/transport/netty4/Netty4Utils.java

@@ -69,9 +69,7 @@ public void testToChannelBuffer() throws IOException {
         BytesReference ref = getRandomizedBytesReference(randomIntBetween(1, 3 * PAGE_SIZE));
         ByteBuf buffer = Netty4Utils.toByteBuf(ref);
         BytesReference bytesReference = Netty4Utils.toBytesReference(buffer);
-        if (ref instanceof ByteBufBytesReference) {
-            assertEquals(buffer, ((ByteBufBytesReference) ref).toByteBuf());
-        } else if (AbstractBytesReferenceTestCase.getNumPages(ref) > 1) { // we gather the buffers into a channel buffer
+        if (AbstractBytesReferenceTestCase.getNumPages(ref) > 1) { // we gather the buffers into a channel buffer
             assertTrue(buffer instanceof CompositeByteBuf);
         }
         assertArrayEquals(BytesReference.toBytes(ref), BytesReference.toBytes(bytesReference));