netty: Add ProtocolNegotiator.close

This notifies the negotiator when it will no longer be used, allowing it
to clean up any resources.

alts/src/main/java/io/grpc/alts/internal/AltsProtocolNegotiator.java

@@ -61,6 +61,11 @@ public abstract class AltsProtocolNegotiator implements ProtocolNegotiator {
                     handshakerFactory.newHandshaker(grpcHandler.getAuthority()))),
             new TsiFrameHandler());
       }
+
+      @Override
+      public void close() {
+        // TODO(jiangtaoli2016): release resources
+      }
     };
   }
 
@@ -75,6 +80,11 @@ public abstract class AltsProtocolNegotiator implements ProtocolNegotiator {
             new TsiHandshakeHandler(new NettyTsiHandshaker(handshakerFactory.newHandshaker(null))),
             new TsiFrameHandler());
       }
+
+      @Override
+      public void close() {
+        // TODO(jiangtaoli2016): release resources
+      }
     };
   }
 

alts/src/main/java/io/grpc/alts/internal/GoogleDefaultProtocolNegotiator.java

@@ -49,4 +49,10 @@ public final class GoogleDefaultProtocolNegotiator implements ProtocolNegotiator
       return tlsProtocolNegotiator.newHandler(grpcHandler);
     }
   }
+
+  @Override
+  public void close() {
+    altsProtocolNegotiator.close();
+    tlsProtocolNegotiator.close();
+  }
 }

netty/src/main/java/io/grpc/netty/NettyChannelBuilder.java

@@ -526,6 +526,7 @@ public final class NettyChannelBuilder
       }
       closed = true;
 
+      protocolNegotiator.close();
       if (usingSharedGroup) {
         SharedResourceHolder.release(Utils.DEFAULT_WORKER_EVENT_LOOP_GROUP, group);
       }

netty/src/main/java/io/grpc/netty/ProtocolNegotiator.java

@@ -43,4 +43,11 @@ public interface ProtocolNegotiator {
    * completed successfully.
    */
   Handler newHandler(GrpcHttp2ConnectionHandler grpcHandler);
+
+  /**
+   * Releases resources held by this negotiator. Called when the Channel transitions to terminated.
+   * Is currently only supported on client-side; server-side protocol negotiators will not see this
+   * method called.
+   */
+  void close();
 }

netty/src/main/java/io/grpc/netty/ProtocolNegotiators.java

@@ -104,6 +104,9 @@ public final class ProtocolNegotiators {
 
         return new PlaintextHandler();
       }
+
+      @Override
+      public void close() {}
     };
   }
 
@@ -117,6 +120,9 @@ public final class ProtocolNegotiators {
       public Handler newHandler(GrpcHttp2ConnectionHandler handler) {
         return new ServerTlsHandler(sslContext, handler);
       }
+
+      @Override
+      public void close() {}
     };
   }
 
@@ -207,6 +213,13 @@ public final class ProtocolNegotiators {
         return new BufferUntilProxyTunnelledHandler(
             proxyHandler, negotiator.newHandler(http2Handler));
       }
+
+      // This method is not normally called, because we use httpProxy on a per-connection basis in
+      // NettyChannelBuilder. Instead, we expect `negotiator' to be closed by NettyTransportFactory.
+      @Override
+      public void close() {
+        negotiator.close();
+      }
     }
 
     return new ProxyNegotiator();
@@ -310,6 +323,9 @@ public final class ProtocolNegotiators {
       };
       return new BufferUntilTlsNegotiatedHandler(sslBootstrap, handler);
     }
+
+    @Override
+    public void close() {}
   }
 
   /** A tuple of (host, port). */
@@ -341,6 +357,9 @@ public final class ProtocolNegotiators {
           new HttpClientUpgradeHandler(httpClientCodec, upgradeCodec, 1000);
       return new BufferingHttp2UpgradeHandler(upgrader, handler);
     }
+
+    @Override
+    public void close() {}
   }
 
   /**
@@ -357,6 +376,9 @@ public final class ProtocolNegotiators {
     public Handler newHandler(GrpcHttp2ConnectionHandler handler) {
       return new BufferUntilChannelActiveHandler(handler);
     }
+
+    @Override
+    public void close() {}
   }
 
   private static RuntimeException unavailableException(String msg) {

netty/src/test/java/io/grpc/netty/NettyClientTransportTest.java

@@ -821,5 +821,8 @@ public class NettyClientTransportTest {
       this.grpcHandler = grpcHandler;
       return handler = new NoopHandler(grpcHandler);
     }
+
+    @Override
+    public void close() {}
   }
 }