HTTP/2 Server Example No Response for HTTP/1.x Only Clients

Motiviation:
The HTTP/2 server example just hangs when a client is using only HTTP with no ALPN or upgrade attempts. We should still send some kind of response.

Modifications:
The HTTP/2 server example has a special handler to detect no upgrade HTTP clients and generate a response.

Result:
Clients that just use HTTP with no upgrade will no appear hung when interacting with the HTTP/2 server example.

example/src/main/java/io/netty/example/http2/server/HelloWorldHttp1Handler.java

@@ -15,7 +15,9 @@
  */
 package io.netty.example.http2.server;
 
+import static io.netty.util.internal.ObjectUtil.checkNotNull;
 import io.netty.buffer.ByteBuf;
+import io.netty.buffer.ByteBufUtil;
 import io.netty.channel.ChannelFutureListener;
 import io.netty.channel.ChannelHandlerContext;
 import io.netty.channel.SimpleChannelInboundHandler;
@@ -31,11 +33,15 @@ import static io.netty.handler.codec.http.HttpHeaderNames.CONTENT_TYPE;
 import static io.netty.handler.codec.http.HttpResponseStatus.CONTINUE;
 import static io.netty.handler.codec.http.HttpResponseStatus.OK;
 import static io.netty.handler.codec.http.HttpVersion.HTTP_1_1;
-
 /**
  * HTTP handler that responds with a "Hello World"
  */
 public class HelloWorldHttp1Handler extends SimpleChannelInboundHandler<HttpRequest> {
+    private final String establishApproach;
+
+    public HelloWorldHttp1Handler(String establishApproach) {
+        this.establishApproach = checkNotNull(establishApproach, "establishApproach");
+    }
 
     @Override
     public void channelRead0(ChannelHandlerContext ctx, HttpRequest req) throws Exception {
@@ -46,6 +52,7 @@ public class HelloWorldHttp1Handler extends SimpleChannelInboundHandler<HttpRequ
 
         ByteBuf content = ctx.alloc().buffer();
         content.writeBytes(HelloWorldHttp2Handler.RESPONSE_BYTES.duplicate());
+        ByteBufUtil.writeAscii(content, " - via " + req.protocolVersion() + " (" + establishApproach + ")");
 
         FullHttpResponse response = new DefaultFullHttpResponse(HTTP_1_1, OK, content);
         response.headers().set(CONTENT_TYPE, "text/plain; charset=UTF-8");

example/src/main/java/io/netty/example/http2/server/HelloWorldHttp2Handler.java

@@ -21,6 +21,7 @@ import static io.netty.example.http2.Http2ExampleUtil.UPGRADE_RESPONSE_HEADER;
 import static io.netty.handler.codec.http.HttpResponseStatus.OK;
 import static io.netty.handler.logging.LogLevel.INFO;
 import io.netty.buffer.ByteBuf;
+import io.netty.buffer.ByteBufUtil;
 import io.netty.channel.ChannelHandlerContext;
 import io.netty.handler.codec.http.HttpServerUpgradeHandler;
 import io.netty.handler.codec.http2.DefaultHttp2Connection;
@@ -112,7 +113,10 @@ public class HelloWorldHttp2Handler extends Http2ConnectionHandler {
                 Http2Headers headers, int streamDependency, short weight,
                 boolean exclusive, int padding, boolean endStream) throws Http2Exception {
             if (endStream) {
-                sendResponse(ctx, streamId, RESPONSE_BYTES.duplicate());
+                ByteBuf content = ctx.alloc().buffer();
+                content.writeBytes(HelloWorldHttp2Handler.RESPONSE_BYTES.duplicate());
+                ByteBufUtil.writeAscii(content, " - via HTTP/2");
+                sendResponse(ctx, streamId, content);
             }
         }
 

example/src/main/java/io/netty/example/http2/server/Http2OrHttpHandler.java

@@ -48,7 +48,7 @@ public class Http2OrHttpHandler extends Http2OrHttpChooser {
 
     @Override
     protected ChannelHandler createHttp1RequestHandler() {
-        return new HelloWorldHttp1Handler();
+        return new HelloWorldHttp1Handler("ALPN Negotiation");
     }
 
     @Override

example/src/main/java/io/netty/example/http2/server/Http2ServerInitializer.java

@@ -19,7 +19,9 @@ package io.netty.example.http2.server;
 import io.netty.channel.ChannelHandlerContext;
 import io.netty.channel.ChannelInboundHandlerAdapter;
 import io.netty.channel.ChannelInitializer;
+import io.netty.channel.SimpleChannelInboundHandler;
 import io.netty.channel.socket.SocketChannel;
+import io.netty.handler.codec.http.HttpMessage;
 import io.netty.handler.codec.http.HttpServerCodec;
 import io.netty.handler.codec.http.HttpServerUpgradeHandler;
 import io.netty.handler.codec.http2.Http2ServerUpgradeCodec;
@@ -66,6 +68,16 @@ public class Http2ServerInitializer extends ChannelInitializer<SocketChannel> {
 
         ch.pipeline().addLast(sourceCodec);
         ch.pipeline().addLast(upgradeHandler);
+        ch.pipeline().addLast(new SimpleChannelInboundHandler<HttpMessage>() {
+            @Override
+            protected void messageReceived(ChannelHandlerContext ctx, HttpMessage msg) throws Exception {
+                // If this handler is hit then no upgrade has been attempted and the client is just talking HTTP.
+                System.err.println("Directly talking: " + msg.protocolVersion() + " (no upgrade was attempted)");
+                ctx.pipeline().replace(this, "http-hello-world",
+                        new HelloWorldHttp1Handler("Direct. No Upgrade Attempted."));
+                ctx.fireChannelRead(msg);
+            }
+        });
         ch.pipeline().addLast(new UserEventLogger());
     }