Make FutureCancelHandler sharable

Author: dagnir

http-clients/netty-nio-client/src/main/java/software/amazon/awssdk/http/nio/netty/internal/ChannelPipelineInitializer.java

@@ -82,7 +82,7 @@ public void channelCreated(Channel ch) {
             pipeline.addLast(new OldConnectionReaperHandler(configuration.connectionTtlMillis()));
         }
 
-        pipeline.addLast(new FutureCancelHandler());
+        pipeline.addLast(FutureCancelHandler.getInstance());
         pipeline.addLast(new UnusedChannelExceptionHandler());
         pipeline.addLast(new LoggingHandler(LogLevel.DEBUG));
     }

http-clients/netty-nio-client/src/main/java/software/amazon/awssdk/http/nio/netty/internal/FutureCancelHandler.java

@@ -18,6 +18,7 @@
 import static software.amazon.awssdk.http.nio.netty.internal.ChannelAttributeKey.EXECUTION_ID_KEY;
 import static software.amazon.awssdk.http.nio.netty.internal.ChannelAttributeKey.REQUEST_CONTEXT_KEY;
 
+import io.netty.channel.ChannelHandler;
 import io.netty.channel.ChannelHandlerContext;
 import io.netty.channel.SimpleChannelInboundHandler;
 import io.netty.util.ReferenceCountUtil;
@@ -28,7 +29,13 @@
  * Closes the channel if the execution future has been cancelled.
  */
 @SdkInternalApi
-public class FutureCancelHandler extends SimpleChannelInboundHandler {
+@ChannelHandler.Sharable
+public final class FutureCancelHandler extends SimpleChannelInboundHandler {
+    private static final FutureCancelHandler INSTANCE = new FutureCancelHandler();
+
+    private FutureCancelHandler() {
+    }
+
     @Override
     protected void channelRead0(ChannelHandlerContext ctx, Object o) {
         ReferenceCountUtil.retain(o);
@@ -48,6 +55,10 @@ public void exceptionCaught(ChannelHandlerContext ctx, Throwable e) {
         }
     }
 
+    public static FutureCancelHandler getInstance() {
+        return INSTANCE;
+    }
+
     private boolean cancelled(ChannelHandlerContext ctx, Throwable t) {
         if (!(t instanceof FutureCancelledException)) {
             return false;

http-clients/netty-nio-client/src/test/java/software/amazon/awssdk/http/nio/netty/internal/FutureCancelHandlerTest.java

@@ -42,7 +42,7 @@
 @RunWith(MockitoJUnitRunner.class)
 public class FutureCancelHandlerTest {
 
-    private FutureCancelHandler handler = new FutureCancelHandler();
+    private FutureCancelHandler handler = FutureCancelHandler.getInstance();
 
     @Mock
     private ChannelHandlerContext ctx;