LiveConnect Applet Architecture Bug with Thread utilization (with SSCCE!)

Discussion in 'Java' started by Richard Maher, Nov 22, 2010.

  1. Hi,

    I make no claim to being either a Javascript or JAVA expert so,
    before
    logging a bug report with SUN/Oracle, I would appreciate those here
    with
    relevant skills casting a critical eye of my small reproducer to see
    if the
    anomalies can be explained as simple pilot error rather than a bug in
    the
    plugin code.

    To reproduce the example locally, save the three text files below to
    the
    filenames and extensions specified. Then: -

    javac -cp "c:\Program Files\Java\jdk1.6.0_22\jre\lib\plugin.jar"
    OutThread.java

    javac -cp ".;c:\Program Files\Java\jdk1.6.0_22\jre\lib\plugin.jar"
    Sleeper.java

    jar -cf Sleeper2.jar Sleeper.class OutThread.class

    NB* The above specified the classpath so as to match my version and
    Windows
    location of the relevant bits from the SDK. Your OS, Java Version and
    SDK
    path may vary or may already be defined.

    Note also there will be some minimal text wrapping to be corrected in
    the
    files.

    Once you have compiled the two classes into the JAR, copy Sleeper2.jar
    and
    dyntest_embed.html to your web root directory. Pull up
    http://127.0.0.1/dyntest_embed.html with your FireBug/DeveloperTools
    Console
    window enabled and your JAVA console enabled and watch what happens.
    It can
    take up to 30,000 iterations or as little as 100 but you will see the
    "hang". (If you become impatient you can add further tabs with the
    same page
    (work the static vars) or load the browser instance and/or machine)

    What I observe and accuse the plugin of doing is allocating the wrong
    work
    to the wrong thread. That is, unlike the documented behaviour that can
    be
    seen at: -
    http://download.oracle.com/javase/6/docs/technotes/guides/jweb/applet/applet_exe
    cution.html#threads
    I believe that something makes the plugin lose track of the Thread
    pool and
    allocate the setBack()/notifyAll() call to the LiveConnect worker
    thread
    (when it should go to "Fred") and horror of horrors, my consumer
    thread
    "Fred" that should be exclusively processing jobs on the queue
    sometimes is
    allocated producer work (getNum()) which leads to an unavoidable
    deadlock
    :-(

    Actual example output: -
    [1]in getNum() 2490 caller [TO3] Thread Applet 1 LiveConnect Worker
    ThreadThread[Applet 1 LiveConnect Worker
    Thread,4,http://127.0.0.1/-threadGroup] hash 19c0bd6
    [1]Queueing work
    [1]Going for wait
    **[2]in getNum() 2409 caller [TO2] Thread
    FredThread[Fred,4,http://127.0.0.1/-threadGroup] hash 1827d1**
    [2]Queueing work
    [2]Going for wait


    This can be observed with FF and/or IE8 (Chrome doesn't seem to fail
    with
    only one tab but with multiple dyntest_embed.html tabs the results can
    be
    reproduced).

    Does it coincide with garbage collection? Is the code/logic
    fundamentally
    flawed? Is it a LiveConnect Thread management bug in desperate need
    of
    correction?

    Cheers Richard Maher

    OutThread.java
    ===========

    /**
    * Copyright (c) Richard Maher
    * All rights reserved.
    */
    import netscape.javascript.JSObject;
    import java.util.ArrayList;
    import java.util.concurrent.*;

    class OutThread extends Thread {
    ArrayList<JSObject> windows;
    BlockingQueue<JSObject> queue;
    JSObject item;

    public OutThread(String name, ArrayList<JSObject> windows,
    BlockingQueue<JSObject> queue) {
    super(name);
    System.out.println("Thread constructor");
    this.setDaemon(true);
    this.windows = windows;
    this.queue = queue;
    }

    private boolean readNext(){
    try {
    System.out.println("before take");
    item = queue.take();
    System.out.println("after take");
    } catch (InterruptedException e) {
    return false;
    }
    return true;
    }

    public void run() {
    while (readNext()) {
    // try {
    System.out.println("before call");
    // sleep((int)(Math.random() * 1000));
    try {
    item.call("dispatcher", null);
    } catch (Exception e){e.printStackTrace();}
    System.out.println("after call");
    // } catch (InterruptedException e) {break;}
    }
    System.out.println("DONE!");
    }
    }

    Sleeper.java
    ========
    /**
    * Copyright (c) Richard Maher
    * All rights reserved.
    */
    import java.applet.Applet;
    import netscape.javascript.JSObject;
    //import netscape.javascript.JSException;
    //import java.lang.InterruptedException;
    import java.util.ArrayList;
    import java.util.concurrent.*;

    public class Sleeper extends Applet {
    private int myNum = 0;
    private int myInstance = 0;
    private JSObject browser;
    private final Object lock = new Object();
    private boolean initFlag = false;
    private boolean idle = true;

    private static OutThread writer;
    private volatile static int appletIndex = 0;
    private volatile static ArrayList<JSObject> windows = new
    ArrayList<JSObject>();
    private static BlockingQueue<JSObject> queue = new
    ArrayBlockingQueue<JSObject>(5);

    public synchronized void init() {
    super.init();
    Thread curr = Thread.currentThread();
    System.out.println(" In Init() " + curr.getName() +
    curr + " hash " + Integer.toHexString(curr.hashCode()));

    try {
    browser = JSObject.getWindow(this); }
    catch (netscape.javascript.JSException e) {
    e.printStackTrace(); }
    catch (Exception e) {
    e.printStackTrace(); }

    synchronized(windows){
    appletIndex++;
    myInstance = appletIndex;
    windows.add(browser);
    if (writer == null){
    writer = new OutThread("Fred", windows, queue);
    writer.start();
    }
    }
    /**
    System.out.println("Before sleep call");
    try {
    Thread.sleep(1000);
    }
    catch (InterruptedException e){
    e.printStackTrace();
    }
    System.out.println("After sleep call");
    */
    myNum = 33;
    initFlag = true;
    }

    public synchronized boolean isDone() {
    Thread curr = Thread.currentThread();
    System.out.println(" In isDone() " + curr.getName() +
    curr + " hash " + Integer.toHexString(curr.hashCode()));
    return initFlag;
    }

    public synchronized int getNum(String caller, JSObject callback){
    if (!idle){
    System.out.println("******* boom *********");
    }
    idle = false;
    int i = myNum++;
    Thread curr = Thread.currentThread();
    System.out.println("["+myInstance+"]"+"in getNum() " + myNum +
    "
    caller " +
    caller + " Thread " + curr.getName() +
    curr + " hash " + Integer.toHexString(curr.hashCode()));

    try {
    synchronized (lock){
    System.out.println("["+myInstance+"]"+"Queueing work");
    queue.put(callback);
    System.out.println("["+myInstance+"]"+"Going for wait");
    lock.wait();
    // Thread.sleep(1000);
    }
    }
    catch (InterruptedException e){
    e.printStackTrace();
    }

    System.out.println("["+myInstance+"]"+"After wait call " + i);
    idle = true;
    return i;
    }

    public void setBack(String caller){
    Thread curr = Thread.currentThread();
    System.out.println("["+myInstance+"]"+"in setBack() " + myNum + "
    caller " +
    caller + " Thread " + curr.getName() +
    curr + " hash " + Integer.toHexString(curr.hashCode()));

    synchronized (lock){
    lock.notifyAll();
    }
    System.out.println("["+myInstance+"]"+"After notify");
    }

    public synchronized void destroy ()
    {
    System.out.println("["+myInstance+"]"+"Shutting down");
    if (writer != null){
    writer.interrupt();
    try {
    writer.join();
    }
    catch (InterruptedException e){
    e.printStackTrace();
    }
    writer = null;
    }

    System.out.println("["+myInstance+"]"+"Checked - out");
    super.destroy();
    }
    }

    dyntest_embed.html
    ==============

    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
    "http://www.w3.org/TR/html4/loose.dtd">

    <html>
    <head>
    <style>

    body
    {
    background-color: aliceblue;
    color: black;
    font-family: Georgia;
    font-size: 12px;
    }

    </style>

    <script type="text/javascript">

    var callNum = 0;
    var chanG;
    var activeTesters = [];
    var ctrl;

    function load()
    {
    var objectTag = "<object ";

    if (/Internet Explorer/.test(navigator.appName)) {
    objectTag = objectTag +
    'classid="clsid:8AD9C840-044E-11D1-B3E9-00805F499D93" ';
    } else {
    objectTag = objectTag +
    'type="application/x-java-applet" ' +
    'archive="http://127.0.0.1/Sleeper2.jar" ';
    }

    objectTag = objectTag +
    'width= "0" height= "0" id="TestApp">' +
    '<param name="archive" value="Sleeper2.jar">' +
    '<param name="codebase" value="http://127.0.0.1/">' +
    '<param name="code" value="Sleeper">' +
    '<param name="java_version" value="1.6+">' +
    '<param name="mayscript" value="true">' +
    '<param name="scriptable" value="true">' +
    '<param name="codebase_lookup" value="false">' +
    '</object>';

    var appletDiv = document.createElement("div");
    appletDiv.innerHTML = objectTag;

    try {
    document.body.appendChild(appletDiv);
    chanG = document.getElementById("TestApp");
    }
    catch(err) {
    alert("Tier3 unable to load applet: -\n" +
    (err.description||err.message));
    chanG = null;
    };

    if (chanG == null) {
    throw new Error("Tier3 was unable to initialize the applet");
    } else {
    try {
    if (!chanG.isDone())
    alert("*******RACE******");
    }
    catch(err) {
    chanG.setAttribute("id",null);
    chanG = null;
    throw new Error("Tier3 unable to load applet: -\n" +
    (err.description||err.message));
    }
    }

    ctrl = new blob();
    var tester1 = new tester(1,1000);
    var tester2 = new tester(2,300);
    var tester3 = new tester(3,500);

    }

    function tester(myId,timer){
    this.myId = myId;
    this.timer = timer;
    var sendIt = function(){ctrl.send("[TO"+myId+"]", fred);};
    var fred = function() {
    if (window.console) console.log("In callback");
    callNum++;
    document.mfForm.username.value=myId+"CB<:"+callNum;
    this.rendezvous();
    if (window.console) console.log("After setBack()");
    document.mfForm.state.value=myId+"CB>:"+callNum;
    setTimeout(sendIt,timer);
    }
    setTimeout(sendIt,0);
    activeTesters.push(this);
    return this;
    }

    function blob(){

    this.chan = chanG;

    return this;
    }

    blob.prototype = {

    send:
    function(msgBody, callback)
    {
    var chan = this.chan;
    var responseCnt = 0;
    var i = 0;

    var msgCandidate =
    {
    msgSeqNum : -1,
    chan : chan,
    callback : callback,

    dispatcher :
    function()
    {
    this.responseCnt++;

    try {
    callback.apply(this);
    }
    catch (err) {
    var errMsg = "Error calling callback
    routine: -\n";
    for (var prop in err) {
    errMsg += " Property: " + prop + " Value:
    " +
    err[prop] + "\n";
    }
    errMsg += " toString() = " + err.toString()
    +
    "\n";

    if (window.console) console.log("Client: "
    +
    errMsg);
    // document.write("Client: " + errMsg);
    throw new Error(errMsg);
    }
    },

    getResponseCnt:
    function() {
    return this.responseCnt;
    },

    rendezvous :
    function() {
    if (window.console) console.log("In
    rendezvous");
    chan.setBack("CB");
    }

    };

    if (window.console) console.log("Before SEND: " + msgBody);
    return chan.getNum(msgBody, msgCandidate);
    }
    }
    </script>
    </head>

    <body id="torso" onload="load()">
    <form name="mfForm">
    Something:
    <input
    name="username";
    type="text";
    size=20;
    />
    Stuff:
    <input
    name="state";
    type="text";
    size=20;
    />
    </form>
    </body>
    </html>
     
    Richard Maher, Nov 22, 2010
    #1
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  2. Richard Maher

    Lew Guest

    Re: LiveConnect Applet Architecture Bug with Thread utilization (withSSCCE!)

    Richard Maher wrote:
    > I make no claim to being either a Javascript or JAVA expert so,
    > before
    > logging a bug report with SUN/Oracle, I would appreciate those here
    > with
    > relevant skills casting a critical eye of my small reproducer to see
    > if the
    > anomalies can be explained as simple pilot error rather than a bug in
    > the
    > plugin code.


    This post looks very similar to the one you posted yesterday with the same
    subject line.

    --
    Lew
     
    Lew, Nov 22, 2010
    #2
    1. Advertising

  3. Lew wrote:
    > Richard Maher wrote:
    > > I make no claim to being either a Javascript or JAVA expert so,
    > > before
    > > logging a bug report with SUN/Oracle, I would appreciate those here
    > > with
    > > relevant skills casting a critical eye of my small reproducer to see
    > > if the
    > > anomalies can be explained as simple pilot error rather than a bug in
    > > the
    > > plugin code.

    >
    > This post looks very similar to the one you posted yesterday with the same
    > subject line.
    >


    Yes, my appologies for those who see both posts. I checked for replies
    this morning via Google groups and there was no trace of my original
    post so I assumed it didn't get through.

    > --
    > Lew


    Cheers Richard Maher
     
    Richard Maher, Nov 22, 2010
    #3
  4. Re: LiveConnect Applet Architecture Bug with Thread utilization (withSSCCE!)

    On 22. 11. 10. 6:33 AM, Richard Maher wrote:

    > Yes, my appologies for those who see both posts. I checked for replies
    > this morning via Google groups and there was no trace of my original
    > post so I assumed it didn't get through.


    I can confirm that as I don't see the original post on c.l.j.programmer.
     
    Screamin' Lord Byron, Nov 22, 2010
    #4
  5. Richard Maher

    Lew Guest

    Re: LiveConnect Applet Architecture Bug with Thread utilization (withSSCCE!)

    Richard Maher wrote:
    >> Yes, my appologies for those who see both posts. I checked for replies
    >> this morning via Google groups and there was no trace of my original
    >> post so I assumed it didn't get through.


    Screamin' Lord Byron wrote:
    > I can confirm that as I don't see the original post on c.l.j.programmer.


    More evidence of the deficiencies of Google Groups.

    --
    Lew
     
    Lew, Nov 22, 2010
    #5
  6. Ok, I went ahead and entered it as a SDN bug and would really
    appreciate it if some of you could spend the time to: -
    http://bugs.sun.com/bugdatabase/addVote.do?bug_id=7001755

    I'm guessing a "Priority 4" bug is not going to get an aweful lot of
    attention so if you agree with me and would like to see it fixed then
    please lend your voice.

    Cheers Richard Maher
     
    Richard Maher, Nov 23, 2010
    #6
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