Hello, Kristian:

Thanks for your response.

I think I found what the problem is... When my IDE (IntelliJ IDEA) hits a breakpoint, it suspends all threads. I find it funny that in all these years of programming and using IDEA, I've never realized it.
(possibly because I was too occupied debugging the code at the breakpoint and not thinking about other threads at that moment). I've searched through the options but couldn't find any setting
which will prevent other threads from being suspended. Will continue looking.

I am now curious, what IDE do you use that it worked for you? And did you need to enable any special settings to allow all other threads to continue execution?

Regards,

Pavel.






Kristian Waagan <Kristian.Waagan@Sun.COM>
Sent by: Kristian.Waagan@Sun.COM

02/16/2010 03:32 AM
Please respond to
"Derby Discussion" <derby-user@db.apache.org>

To
Derby Discussion <derby-user@db.apache.org>
cc
Subject
Re: Using NetworkServerControl to access in-memory (only) tables of Embedded Derby





On 16.02.10 03:02, Pavel Bortnovskiy wrote:
> Bryan: thank you for your response.
>
> I do see the thread you mention:
>
>          Thread Group [derby.daemons]{10}(Daemon)
>              Thread [derby.antiGC]{1}(Daemon)(WAITING)
>              Thread [derby.rawStoreDaemon]{5}(Daemon)(TIMED_WAITING)
>              Thread [derby.NetworkServerStarter]{5}(Daemon)(WAITING)
>              Thread [NetworkServerThread_2]{5}(Daemon)(RUNNABLE)
>              Thread [DRDAConnThread_3]{5}(Daemon)(WAITING)
>
> However the behavior is still the same - if any other thread stops (for
> instance in debugger), NetworkServerControl becomes unresponsive.
> For instance, if I connect to it from the "outside" with another db app
> (Aqua Data Studio, for instance), then connection to it breaks or the db
> app can't access it.
> But as soon as I let the thread run in that debugger, the connection
> becomes alive and everything seems to work.
>
> Has anyone else seen this kind of behavior?
> Or perhaps, someone can share a piece of code (best practice) of how to
> instantiate and run the NetworkServerControl, so that it's not
> experiencing
> such hang-ups.
>    

Hi Pavel,

The code I'm about to post is by no means to be considered best
practice, but I think it does what you want it to do. However, the code
is basically yours :) (I copied it from your mail)
When I hit the breakpoint (set on the System.out.println in the static
main method), the ping thread continued to run, and I could also access
and do things with the database through ij.

Are you sure you're only stopping the current thread in your debugger?
When the system appears to hang, can you obtain a stack trace (using
jstack or similar) and check what the Derby threads are doing?
Are you sure your stopped thread isn't holding on to some monitors /
locks required by the other threads? (sounds unlikely, as the Derby
threads should operate on their own, but I'm asking anyway...)

See the code I tested with below (I'm using localhost as host, so you
cannot connect to Derby remotely).


Regards,
--
Kristian


import java.io.PrintWriter;
import java.net.InetAddress;
import java.util.concurrent.atomic.AtomicBoolean;
import org.apache.derby.drda.NetworkServerControl;

public class ServerTestDebug implements Runnable {

    private final InetAddress m_host;
    private final int m_port = 1527;
    private final AtomicBoolean m_done = new AtomicBoolean(false);
    private final int m_sleep = 5000;

    private NetworkServerControl m_server;

    public ServerTestDebug()
            throws Exception {
        m_host = InetAddress.getByName("localhost");
    }

  final public void start() throws Exception {
    new Thread(this, "Derby Server").start();
  }

  public void stop() {
      System.out.println("Telling server to stop...");
      m_done.set(true);
  }

  public void run() {
      try {
        m_server = new NetworkServerControl(m_host, m_port);
        m_server.start(new PrintWriter(System.out));
      } catch (Exception e) {
            e.printStackTrace(System.out);
            return;
      }

    try {
      while (!m_done.get()) {
            System.out.println("pinging...");
            m_server.ping();

        try {
          Thread.sleep(m_sleep);
        } catch (InterruptedException e) {
          /* log */
        }
      }
    } catch (Exception e) {
      /* log - errror pinging server */
    }
      try {
          System.out.println("Shutting down...");
        m_server.shutdown();
      } catch (Exception e) {
          e.printStackTrace();
      }
  }

    public static void main(String[] args)
            throws Exception {
        ServerTestDebug server = new ServerTestDebug();
        server.start();
        System.out.println("Starting main loop...");
        int iterations = 30;
        while (iterations > 0) {
            if (iterations == 20) {
               System.out.println("breakpoint here!");
            }
            try {
                Thread.sleep(2000);
            } catch (InterruptedException ie) { }
            iterations--;
        }
        server.stop();
    }
}





> Much appreciated,
>
> Pavel.
>
>
>
>
>
>
>
>
>
>
>
> Bryan Pendleton<bpendleton@amberpoint.com>
> 02/05/2010 12:07 PM
> Please respond to
> "Derby Discussion"<derby-user@db.apache.org>
>
>
> To
> Derby Discussion<derby-user@db.apache.org>
> cc
>
> Subject
> Re: Using NetworkServerControl to access in-memory (only) tables of
> Embedded Derby
>
>
>
>
>
>
>    
>> DerbyServer thread seems to still be running, yet the server is
>> unresponsive.
>>      
> In addition to your own DerbyServer thread, which I don't think
> actually *needs* to still be running, there should be a separate
> thread which is started by the Derby network server code itself,
> which has the job of accepting connections and delivering them
> to other threads to be processed.
>
> In my running network server, for example, when I look at the
> threads that are active, I see:
>
> "NetworkServerThread_2" prio=6 tid=0x03044c80 nid=0x27c runnable
> [0x033cf000..0x033cfae8]
>           at java.net.PlainSocketImpl.socketAccept(Native Method)
>           at java.net.PlainSocketImpl.accept(PlainSocketImpl.java:384)
>           - locked<0x22a857d8>  (a java.net.SocksSocketImpl)
>           at java.net.ServerSocket.implAccept(ServerSocket.java:450)
>           at java.net.ServerSocket.accept(ServerSocket.java:421)
>           at org.apache.derby.impl.drda.ClientThread$1.run(Unknown Source)
>           at java.security.AccessController.doPrivileged(Native Method)
>           at org.apache.derby.impl.drda.ClientThread.run(Unknown Source)
>
> Do you see a thread like that?
>
> When your server becomes stuck/wedged/unresponsive, why don't you try
> this:
>    - collect a thread dump of the entire JVM
>    - look through the threads for any which mention "org.apache.derby" in
> their stacks
>    - edit out all the other threads from your thread dump
>
> Then post a message with a cut-and-paste of just the derby-related threads
> in your wedged server, and maybe it will be more clear to somebody else
> what the problem is.
>
> thanks,
>
> bryan
>
>
>
>
>
>
>
>
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