FULL PRODUCT VERSION :
java version " 1.7.0_15 "
Java(TM) SE Runtime Environment (build 1.7.0_15-b03)
Java HotSpot(TM) 64-Bit Server VM (build 23.7-b01, mixed mode)

or

java version " 1.6.0_27 "
OpenJDK Runtime Environment (IcedTea6 1.12.3) (6b27-1.12.3-0ubuntu1~12.04.1)
OpenJDK 64-Bit Server VM (build 20.0-b12, mixed mode)


ADDITIONAL OS VERSION INFORMATION :
Linux i5 3.2.0-38-generic #61-Ubuntu SMP Tue Feb 19 12:18:21 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux


A DESCRIPTION OF THE PROBLEM :
HttpServer and URLConnection introduce a 38 ms delay when using keep-alive.


REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
/**
 * @test
 * @bug
 * @summary pipelining delay on Ubuntu 12.04.01 LTS / amd64
 */

import com.sun.net.httpserver.*;

import java.util.*;
import java.util.concurrent.*;
import java.io.*;
import java.net.*;

public class Bug {

    static int iterations = 20;
    static long requiredMinimumDelay = 10L;
    
    public static void main (String[] args) throws Exception {
        Handler handler = new Handler();
        InetSocketAddress addr = new InetSocketAddress (8075);
        HttpServer server = HttpServer.create (addr, 0);
        HttpContext ctx = server.createContext ( " /test " , handler);
        ExecutorService executor = Executors.newCachedThreadPool();
        server.setExecutor (executor);
        server.start ();

        long minDelay = requiredMinimumDelay * 1000L;
        
        try {
            for(int i = 0; i < iterations; i++) {
                URL url = new URL ( " http://localhost: " +server.getAddress().getPort()+ " /test/foo.html " );
                HttpURLConnection urlc = (HttpURLConnection)url.openConnection ();
                InputStream is = urlc.getInputStream();
                InputStreamReader isr = new InputStreamReader(is);
                BufferedReader br = new BufferedReader(isr);
                String res = br.readLine();
                br.close();
                
                // skip first few
                if(i < iterations/2) {
                    continue;
                }
                
                long delay = System.currentTimeMillis() - Long.parseLong(res);
                System.out.println( " delay: " +delay+ " ms " );
                if(delay < minDelay) {
                    minDelay = delay;
                }
            }
        } catch (Exception ex) {}
        
        server.stop(2);
        executor.shutdown();
        
        if(minDelay > requiredMinimumDelay) {
            throw new Exception( " minimum delay too large: " +minDelay);
        }
    }

    static class Handler implements HttpHandler {
        public void handle (HttpExchange t)
            throws IOException
        {
            InputStream is = t.getRequestBody();
            Headers map = t.getRequestHeaders();
            Headers rmap = t.getResponseHeaders();
            while (is.read () != -1) ;
            is.close();
            String response = Long.toString(System.currentTimeMillis())+ "
 " ;
            t.sendResponseHeaders (200, response.length());
            OutputStream os = t.getResponseBody();
            os.write (response.getBytes());
            t.close();
        }
    }
}


---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Connection: close