How to use Netty to handle Http Keep-Alive connections

Question

I'm trying to write a HTTP client that uses HTTP keep-alive connections. When I connection from the ClientBoostrap I get the channel. Can I reuse this for sending multiple HTTP requests? Is there any examples demonstrating the HTTP Keep Alive functionality?

Also I have another question. Now my client works without keep-alive connections. I'm calling the channel.close in the messageReceived method of the ClientHandler . But it seems the connections are not getting closed and after some time the sockets run out and I get a BindException . Any pointers will be really appreciated.

Thanks

Answer 1

As long as the Connection header is not set to CLOSE (and possible the HttpVersion is 1.1, though uncertain) by a line of code similar to this...

request.setHeader(HttpHeaders.Names.CONNECTION, HttpHeaders.Values.CLOSE);

...your channel should remain open for multiple request/response pairs.

Here is some example code that I whipped up today to test it. You can bounce any number of requests off of Google prior to the channel closing:

 public class TestHttpClient {
    static class HttpResponseReader extends SimpleChannelUpstreamHandler {
        int remainingRequests = 2;

        @Override
        public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) throws Exception {
            HttpResponse response = (HttpResponse) e.getMessage();

            System.out.println("Beginning -------------------");
            System.out.println(new String(response.getContent().slice(0, 50).array()));
            System.out.println("End -------------------\n");

            if(remainingRequests-- > 0)
                sendRequest(ctx.getChannel());
            else
                ctx.getChannel().close();
        }
    }

    public static void main(String[] args) {
        ClientBootstrap bootstrap = new ClientBootstrap(new NioClientSocketChannelFactory());
        bootstrap.setPipeline(Channels.pipeline(
                new HttpClientCodec(),
                new HttpResponseReader()));
        // bootstrap.setOption("child.keepAlive", true); // no apparent effect

        ChannelFuture future = bootstrap.connect(new InetSocketAddress("google.com", 80));
        Channel channel = future.awaitUninterruptibly().getChannel();

        channel.getCloseFuture().addListener(new ChannelFutureListener() {
            public void operationComplete(ChannelFuture future) throws Exception {
                // this winds up getting called immediately after the receipt of the first message by HttpResponseReader!
                System.out.println("Channel closed");
            }
        });

        sendRequest(channel);

        while(true) {
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    private static void sendRequest(Channel channel) {
        // Prepare the HTTP request.
        HttpRequest request = new DefaultHttpRequest(
                HttpVersion.HTTP_1_1, HttpMethod.GET, "http://www.google.com");
        request.setHeader(HttpHeaders.Names.HOST, "google.com");
        request.setHeader(HttpHeaders.Names.ACCEPT_ENCODING, HttpHeaders.Values.GZIP);

        channel.write(request);
    }
}