Re: [Simpleweb-Support] FIX: Simple stops responding
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Re: [Simpleweb-Support] FIX: Simple stops responding
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From: Andrew M. <and...@ya...> - 2005-08-04 17:29:41
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Ok, I'm sure it's an absolutely horrible implementation but this is what
I did (keep in mind I'm not sure this is the same problem, but it seems
to have the same symptoms).
public class BlockingQueue {
private Link first;
private Link last;
private int maxWait = 100;
public BlockingQueue() {}
public BlockingQueue(int wait) {
maxWait = wait;
}
public void add(Object o) {
if (o == null) throw new NullPointerException();
synchronized(this) {
if (first == null) {
first = new Link(o);
first.timeout = -1;
last = first;
}
else {
last.next = new Link(o);
last.next.timeout = -1;
}
notify();
}
}
public void add(Object o, long wait) {
if (o == null) throw new NullPointerException();
synchronized(this) {
if (first == null) {
first = new Link(o);
first.timeout = System.currentTimeMillis() +
Math.min(wait,maxWait);
last = first;
}
else {
last.next = new Link(o);
last.next.timeout = System.currentTimeMillis() +
Math.min(wait,maxWait);
}
notify();
}
}
public Object getNext() throws InterruptedException {
synchronized (this) {
while (first == null) wait();
sleepUntil(first.timeout);
Object o = first.value;
first = first.next;
return o;
}
}
public void clear() {
first = null;
last = null;
}
private class Link {
public Link next;
public Object value;
public long timeout;
public Link(Object value) {this.value = value;}
}
protected void sleepUntil(long awaken) throws InterruptedException {
long time = System.currentTimeMillis();
long sleep = awaken - time;
if(sleep <= 0) return;
Thread.sleep(sleep);
}
}
Niall Gallagher wrote:
>Hi Andrew,
>
>I would like to see your implementation! I have
>searched through all classes in the
>simple.util.schedule package and also tested them, and
>I had not found errors or deadlock situations? Perhaps
>I can learn somthing from your implementation that I
>have overlooked. I would certainly appreciate it!
>
>Niall
>
>--- Andrew Madigan <and...@ya...> wrote:
>
>
>
>>Alright I've taken another look at the the code I
>>used, this is what
>>I've figured out:
>>- I assumed that simple used
>>util.schedule.SchedulerQueue and that this
>>was causing problems
>>- I replaced the use of this class (still trying to
>>find where) with a
>>different implementation that used a simpler method
>>of blocking
>>and did not use arrays
>>- As I said I am no threading expert so there are
>>probably flaws in my
>>queue implementation, but I have never had problems
>>with it and I use it
>>in the application that I run on top of simple as
>>well.
>>
>>If you would like me to post the code for the queue
>>I will just let me know.
>>
>>Jorge CAMPOS wrote:
>>
>>
>>
>>>Hi everybody!
>>>
>>>>From our tests with our application, it seems that
>>>
>>>
>>Simple hangs only when
>>
>>
>>>using at least 35 threads in parallel (we're
>>>
>>>
>>testing in a 4Way Xeon with HT
>>
>>
>>>running SuSE SLES 9.0 and JDK 1.5.0_04). From the
>>>
>>>
>>thread dump and some
>>
>>
>>>printlns in the code it seems that one thread
>>>
>>>
>>(dequeuer) blocks because
>>
>>
>>>there are no more requests to be processed. After
>>>
>>>
>>that everything starts
>>
>>
>>>piling up (all the dequeuers wait for the first one
>>>
>>>
>>and the enqueuers too).
>>
>>
>>>I know it sound a bit weird, but it could be
>>>
>>>
>>related to the locking queue
>>
>>
>>>implementation.
>>>
>>>I've tried to reproduce the problem using the demo
>>>
>>>
>>server and I didn't
>>
>>
>>>succeed. I guess the context is different (to
>>>
>>>
>>simulate some load I've put
>>
>>
>>>one sleep and some printlns). This made me look
>>>
>>>
>>again at our thread dump...
>>
>>
>>>and I can't see anything related to our application
>>>
>>>
>>(it seems that Simple
>>
>>
>>>blocks within its code).
>>>
>>>One question Andrew: what are the specs of your
>>>
>>>
>>machine?
>>
>>
>>>I'm asking this, because I've seen some locking
>>>
>>>
>>problems in applications
>>
>>
>>>running with HyperThreading ON.
>>>
>>>We will test the application running with
>>>
>>>
>>HyperThreading off and in another
>>
>>
>>>machine to see if we can reproduce the problem.
>>>
>>>All your support is greatly appreciated.
>>>
>>>Ah, one more thing. Since in our thread dump it
>>>
>>>
>>seems all the threads are
>>
>>
>>>still alive, I don't think this particular case
>>>
>>>
>>relates to a out of memory
>>
>>
>>>exception (also there are no exceptions in the
>>>
>>>
>>logs)
>>
>>
>>>Jorge
>>>
>>>-----Original Message-----
>>>From: sim...@li...
>>>
>>>
>>[mailto:sim...@li...]On
>>Behalf Of Niall
>>
>>
>>>Gallagher
>>>Sent: Wednesday, August 03, 2005 10:21 AM
>>>To: sim...@li...
>>>Subject: Re: [Simpleweb-Support] FIX: Simple stops
>>>
>>>
>>responding
>>
>>
>>>Hi,
>>>
>>>I have taken note of the last two comments with
>>>
>>>
>>regard
>>
>>
>>>to the server freezing! In response to the queue
>>>implementation, I think that the implementation of
>>>
>>>
>>the
>>
>>
>>>Scheduler, ObjectQueue, and ProcessQueue involved
>>>
>>>
>>in
>>
>>
>>>dispatching requests is fine. There are no problems
>>>here.
>>>
>>>However, the simple.http.connect implementation may
>>>
>>>
>>be
>>
>>
>>>at fault, and I have no doubt whatsoever that the
>>>java.lang.OutOfMemory error will cause the server
>>>
>>>
>>to
>>
>>
>>>stop responding under very heavy load.
>>>
>>>I have uploaded my test framework for anyone
>>>
>>>
>>wishing
>>
>>
>>>to use it to see if it will freeze their server.
>>>
>>>
>>If
>>
>>
>>>it does then great! let me know what happened.
>>>However, I have put through well over a 100 million
>>>requests using my test framework today alone and,
>>>
>>>
>>with
>>
>>
>>>the catch(Throwable) amendments there is no
>>>
>>>
>>deadlock,
>>
>>
>>>not even a lost thread.
>>>
>>>The test framework can be downloaded at
>>>http://simpleweb.sf.net/simple-test.tar.gz.
>>>
>>>So, in conclusion, the application is thread safe
>>>
>>>
>>and
>>
>>
>>>working properly with catch(Throwable) amendments.
>>>However, the TCP related issues have not been
>>>
>>>
>>thought
>>
>>
>>>out carefully! And I believe the
>>>
>>>
>>simple.http.connect
>>
>>
>>>package needs to be reworked! I will release all
>>>
>>>
>>the
>>
>>
>>>bug fixes as soon as I am convinced everything is
>>>working.
>>>
>>>Thanks for the bug reports, if anyone thinks the
>>>freeze is related to somthing else please let me
>>>
>>>
>>know
>>
>>
>>>so that I can explore it!
>>>
>>>Niall
>>>
>>>
>>>Niall Gallagher
>>>
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>
>>>_______________________________________________
>>>Simpleweb-Support mailing list
>>>Sim...@li...
>>>
>>>
>>https://lists.sourceforge.net/lists/listinfo/simpleweb-support
>>
>>
>>>
>>>
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>>
>>
>>
>>
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>>
>>
>>
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>
>
>
>Niall Gallagher
>
>
>
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