Re: [Wicket-user] wicket ajax memory leak with IE

Ari Suutari Mon, 17 Apr 2006 22:34:04 -0700

Hi,

As far as I know IE won't fire more than two simultanous http request.
So i'm not quite sure about it.


   OK, I don't know how real this problem would be anyway. However,
   something still leaks slowly: I left a wicket page using 
AjaxSelfUpdatingTimer

(which fires once per second) running over easter. When I came back tooffice today, the page was still updating itself but internet explorer

   was a log bigger (like 10x).

   But things are a *lot* better now - before a test like this would have
   crashed the browser.

       Ari S.


-Matej

Ari Suutari wrote:

I found one potential (minor) problem: if timer creates ajax requests
so frequently that web server lags behind the the system leaks
again because it needs to always allocate new transport object
since all existing ones are busy ? Maybe there should be some
kind of upper limit for transport pool.

Maybe this isn't any more such a big problem for most folks.
It occurs me when updating a label with 100 ms timer (well, actually,
maybe the timer in AjaxSelfUpdatingTimerBehavour shouldn't fire
until previous request has completed ?)

   Ari S.

----- Original Message ----- From: "Matej Knopp" <[EMAIL PROTECTED]>
To: <wicket-user@lists.sourceforge.net>
Sent: Wednesday, April 12, 2006 9:51 PM
Subject: Re: [Wicket-user] wicket ajax memory leak with IE

Hi, I made some changes, this really helps, at least it works for me:

// AJAX FUNCTIONS
function wicketAjaxCreateTransport() {
    var transport = null;
    if (window.XMLHttpRequest) {
        transport = new XMLHttpRequest();
    } else {
        if (window.ActiveXObject) {
            transport = new ActiveXObject("Microsoft.XMLHTTP");
        }
    }

    if (transport==null&&wicketAjaxDebugEnabled()) {
        var log=WicketAjaxDebug.logError;

log("Could not locate ajax transport. Your browser does notsupport the required XMLHttpRequest object or wicket could not gainaccess to it.");

    }
    return transport;
}

var wicketAjaxTransports = [];


function wicketAjaxGetTransport() {
var t = wicketAjaxTransports;
for (var i = 0; i < t.length; ++i) {
if (t[i].readyState == 0 || t[i].readyState == 4) {
return t[i];
}
}
t[t.length] = wicketAjaxCreateTransport();
return t[t.length-1];
}

function wicketAjaxGet(url, successHandler, failureHandler) {
    if (wicketAjaxDebugEnabled()) {
        var log=WicketAjaxDebug.logInfo;
        log("");
        log("initiating ajax GET request with...");
        log("url: "+url);
        log("successHandler:"+successHandler);
        log("failureHandler:"+failureHandler);
    }

    var transport = wicketAjaxGetTransport();
    if (transport == null) {
        return false;
    }
    transport.open("GET", url + "&random=" + Math.random(), true);
    transport.onreadystatechange = function () {

wicketAjaxOnStateChange(transport, successHandler,failureHandler);

        if (transport.readyState == 4) {
        transport.onreadystatechange = function () {};
        transport = null;
        }
    };
    transport.send(null);

    return true;
}
function wicketAjaxPost(url, body, successHandler, failureHandler) {
    if (wicketAjaxDebugEnabled()) {
        var log=WicketAjaxDebug.logInfo;
        log("");
        log("initiating ajax POST request with...");
        log("url: "+url);
        log("body: "+body);
        log("successHandler:"+successHandler);
        log("failureHandler:"+failureHandler);
    }

    var transport = wicketAjaxGetTransport();
    if (transport == null) {
        return false;
    }
    transport.open("POST", url + "&random=" + Math.random(), true);
    transport.onreadystatechange = function () {

wicketAjaxOnStateChange(transport, successHandler,failureHandler);

        if (transport.readyState == 4) {
        transport.onreadystatechange = function () {};
        transport = null;
        }
    };

transport.setRequestHeader("Content-Type","application/x-www-form-urlencoded");

    transport.send(body);

    return true;
}

Matej Knopp wrote:

I guess I have seen one. But it shouldn't be that difficult to get itdone. I guess I might be able to look into it tonight.
-Matej

Igor Vaynberg wrote:
is there a pooling implementation somewhere i can take a look at andborrow, im not really inerested in becoming a javascript wiz justbecause ms cant get it right.
-Igor
On 4/12/06, *Matej Knopp* <[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>>wrote:
    AFAIK There's nothing wrong with javascript. The problem is that
    creating XMLHttpRequest every time causes memory leak in IE.
People tend to reuse one instance of xmlhttprequest, but thatdoes notsuffice here, i guess, therefore I suggested xmlhttprequestsinstances
    pooling.

    I tried to reuse one instance of xmlhttprequest and the leak was no
    longer there. At least with the test application. (The one in this
    thread).
The only thing when you are "reusing" XmlHttpRequests is thatyou must
    call transport.open before you assign transport.onreadystate = ...
    (some weird IE related thing)

    -Matej

    Igor Vaynberg wrote:
> i looked through the javascript but nothing jumped out at me.did
    you
     > notice anything cause im stumped.
     >
     > -Igor
     >
     > On 4/12/06, *Matej Knopp* < [EMAIL PROTECTED]
    <mailto:[EMAIL PROTECTED]> <mailto:[EMAIL PROTECTED]
    <mailto:[EMAIL PROTECTED]> >> wrote:
     >
> Yeah, it is. However, it's much smaller. But still, 10-15kb per
     >     request.
     >
     >     -Matej
     >
     >     Igor Vaynberg wrote:
     >      > is the leak still there if you turn off the ajax debug
    mode in
     >      > IAjaxSettings?
     >      >
     >      > -Igor
     >      >
     >      >
     >      > On 4/12/06, *Matej Knopp* < [EMAIL PROTECTED]
    <mailto:[EMAIL PROTECTED]>
     >     <mailto: [EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>>
    <mailto:[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>
     >     <mailto:[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>>>> wrote:
     >      >
     >      >     Ari Suutari wrote:
     >      >      >> need several requests at the same time. So maybe
    pooling of
     >      >      >> XmlHttpRequest(s) could work...
     >      >      >
> > > Btw, does dojo use pooling (since there wasno leak
     >     with it) ?
     >      >      >    Maybe it would make sense to check how they are
    getting
     >     around
     >      >      >    this.
     >      >      >
     >      >      >        Ari S.
     >      >      >
> > Don't know, might be worth checking. But dojocodebase is
     >     quite big and
     >      >     the code little hard to read, mostly because dojo
    handles a
     >     lot of other
     >      >     things (back button support, etc.)
     >      >
     >      >     -Matej
     >      >      >>
     >      >      >> -Matej
     >      >      >>
     >      >      >> Ari Suutari wrote:
     >      >      >>> Hi,
     >      >      >>>
     >      >      >>> There is a browser-side memory leak in wicket
    ajax stuff
     >     when used
     >      >      >>> with internet explorer. We discovered it when
    changing our
     >      >     application
     >      >      >>> from wichet+dojo to wicket+wicket-ajax.
     >      >      >>>
> > >>> Memory leak occurs only if wicket-ajax isused in IE.
     >     With dojo,
     >      >      >>> there is on leak. Also, in firefox, neither
    solution leaks.
     >      >      >>>
     >      >      >>> There is a simple example available at
     >      >      >>>
     >      >      >>>
     >     http://download.syncrontech.com/public/wicketajaxleak.zip
     >     <http://download.syncrontech.com/public/wicketajaxleak.zip>
     >      >     <
    http://download.syncrontech.com/public/wicketajaxleak.zip>
     >      >      >>>
     >      >      >>> It just displays a number, increments it and
    displays it
     >     again
     >      >      >>> using ajax.
     >      >      >>>
> > >>> There is also a memory usage graph which hasdata
    from
     >      >      >>> dojo and wicket-default ajax cases, from that it
    is easy
> > >>> to see how differenty these implementationsbehave.
     >      >      >>>
> > >>>http://download.syncrontech.com/public/wicketajax.gif
     >     <http://download.syncrontech.com/public/wicketajax.gif>
     >      >      >>>
     >      >      >>> These runs were done agains wicket 1.2-beta3.
     >      >      >>> This is a rather nasty problem for us, since we
    have a lot
> > >>> of pages, which update themselves veryfrequently
    based on
     >      >      >>> data coming from automation systems.
     >      >      >>>
     >      >      >>> We did some looking around in wicket-ajax.js but
    didn't
     >      >      >>> find anything obvious.
     >      >      >>>
     >      >      >>>    Ari S.
     >      >      >>>
     >      >      >>>
     >      >      >>>
     >      >      >>>
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Re: [Wicket-user] wicket ajax memory leak with IE

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