Fix memory leak when OOM (#15207)

Author: AlbumenJ

dubbo-remoting/dubbo-remoting-netty4/src/main/java/org/apache/dubbo/remoting/transport/netty4/NettyChannel.java

@@ -44,6 +44,7 @@
 import io.netty.channel.ChannelFuture;
 import io.netty.channel.ChannelFutureListener;
 import io.netty.handler.codec.EncoderException;
+import io.netty.util.ReferenceCountUtil;
 
 import static org.apache.dubbo.common.constants.CommonConstants.DEFAULT_ENCODE_IN_IO_THREAD;
 import static org.apache.dubbo.common.constants.CommonConstants.DEFAULT_TIMEOUT;
@@ -185,10 +186,11 @@ public void send(Object message, boolean sent) throws RemotingException {
 
         boolean success = true;
         int timeout = 0;
+        ByteBuf buf = null;
         try {
             Object outputMessage = message;
             if (!encodeInIOThread) {
-                ByteBuf buf = channel.alloc().buffer();
+                buf = channel.alloc().buffer();
                 ChannelBuffer buffer = new NettyBackedChannelBuffer(buf);
                 codec.encode(this, buffer, message);
                 outputMessage = buf;
@@ -224,6 +226,10 @@ public void operationComplete(ChannelFuture future) throws Exception {
             }
         } catch (Throwable e) {
             removeChannelIfDisconnected(channel);
+            if (buf != null) {
+                // Release the ByteBuf if an exception occurs
+                ReferenceCountUtil.safeRelease(buf);
+            }
             throw new RemotingException(
                     this,
                     "Failed to send message " + PayloadDropper.getRequestWithoutData(message) + " to "