HTTPService + XML Load + Memory Leak

Question

Hi all....
I have noticed a memory leak in my application. This leak was
not apparent when the application was completed some months back
which is what left me a little confused as all I have done since
was upgrade to Flex 3 and possibly updated / changed my Flash
player.
I think I have found the cause to this problem (below) but am
not 100% sure that it is the "actual" problem or any reasons to
back my thoughts up, so have listed what I have checked / tried
along the way (maybe I have missed something)....
My Discovery Process:
I started profiling my application but did not find anything
out of the ordinary. I did a code walk-through double checking I
had cleaned up after myself, removing and even nulling all items
etc but still to now success - the leak is still there.
I have profiled the app in the profiler for reasonably long
periods of time.
All the classes etc being used within the app are consistent
in size and instance amount and there is no sign of any apparent
leak.
I am using a HTTPService that is loading XML data which I am
refreshing every 5 seconds. On this 5 second data refresh some
class instances are incremented but are restored to the expected
amount after a GC has occurred. The GC seems to take longer, the
longer the app is running, therefore more and more instances are
being added to the app, but when the GC eventually runs it "seems"
to clear these instances to the expected amount.
After scratching my head for a while I decided to make a copy
of my application, rip everything out, and focus in my data load,
where I found a problem!
I have now just a HTTPService that loads an XML file every 5
seconds, and this is all I currently have in the app (as I ripped
the rest of the code out), e.g:
Code:
<mx:Application xmlns:mx="
http://www.adobe.com/2006/mxml"
....... creationComplete="initApp()" >
<mx:HTTPService
id="httpServiceResults"
url="
http://myIP:myPort/myRoot/myXML.cfm"
resultFormat="e4x"
result="httpResultHandler(event)" />
<script....... >
private var timerPulse:Timer;
private function initApp():void
httpServiceResults.send();
timerPulse = new Timer(5000, 0);
private function httpResultHandler(event:ResultEvent):void
timerPulse.start();
timerPulse.addEventListener(TimerEvent.TIMER, timerRefresh);
public function timerRefresh(eventObj:TimerEvent):void
timerPulse.stop();
timerPulse.removeEventListener(TimerEvent.TIMER,
timerRefresh);
timerPulse.reset();
httpServiceResults.send();
</script>
</mx:Application>
This is pretty much the code I am currently using and it
leaks.
I ran and monitored this in both the profiler and the
activity / task manager, and after running the app for 1800 seconds
(30 min) in the profiler, the memory size grew from 50mg to 165mg
just sending the HTTPService.
I tried loading the service in multiple ways including in AS
rather than MXML creating new instances of it each time, resetting
it, nulling it etc... but nothing prevented this memory increase.
I then tried to load the XML using different methods such as
using the URLRequest and URLLoader which again caused a memory
leak.
What still confuses me is that this leak did not exist in the
previous version and not a great deal has changed since then apart
from upgrading to Flex 3 and possibly upgrading my Flash payer
(which I believe is a possible cause)
After looking into this issue a bit more deeply, I read a few
blogs / forums and other people are experiencing the same problems
- even with a lot bigger leaks in some cases all when reloading
large sets of XML data into Flex - however, I as of yet found no
solution to this leak - people with a similar problem believe it is
not due to a memory leak more a GC error, and others pointing
towards the Flash Player itself that is leaking - I don't really
know.
Findings so far during investigation of this issue:
* App leaks for both HTTPService and ULRRequest / URLLoader
methods
* App only leaks when calling a data loader
* The size of the leak seems to depend on the size of the
XML being loaded
* The size of the leak also seems to be affected by the
applications heaviness - the greater seems to enhance the leak
An interesting factor I have noticed is that if I copy the
XML from my "myXML.cfm" that I link to in my HTTPService and copy
the contents of the file into my own XML file stored within the
Flex project root itself: ""myXML.xml"" the leak disappears... like
it seems to link when loading the XML over a network, however as my
network knowledge is not great I am not sure what to make of this -
any ideas???
Could the connection to the XML document cause leaks??? is
there anything else that could cause this leak??? have I something
in my code sample that could cause this leak??? or could any of the
other things I have mentioed cause this leak???
Any help / ideas would be greatly appreciated.
Thanks,
Jon.

Answer 1

I also observed heavy memory leak from using httpservice with
XML data. I am using Flex3 builder under Linux. My Flex application
polls httpservice every 10 seconds. The reply is a short XML
message less than 100 bytes. This simple polling will consume 30+
MB of memory every hour. I leave it idling for several hours and it
took 200 MB of memory. No sign of garbage collection at all.