Re: [Springframework-developer] CachedIntrospectionResults leak?

[Guillaume P. <gpo...@gl...>]

Andy=2C

What you are seeing there is a symptom=2C not the cause of your leak=2E  =
What cause the leak is that the ClassLoader is never collected=2C in whic=
h case the CachedIntrospectionResults are of little effect in comparaison=
 to the memory taken by every classes and their static members=2E  If you=
r ClassLoader is not collected=2C you might even have external resources =
not freed=2C such as JDBC Connections=2C if you have a reference from a s=
tatic member to your connection pool (directly or indirectly)=2E

Any servlet container will release the ClassLoader when the webapp is unl=
oaded=2C but there=27s many things (bugs) that might prevent the ClassLoa=
der to be collected=2E  The most probable causes I was personally able to=
 identify are the cache in  java=2Elang=2EIntrospector=2C a Driver left u=
nregistered in DriverManager or ThreadLocal variable not cleared=2E  But =
in any case=2C unless there was a bug in the patch I provided=2C or that =
it somehow got broken since (in both cases I doubt it)=2C then code in Ca=
cheIntrospectionResults will never prevent the ClassLoader to be garbage =
collected=2E

So=2C most likely=2C it=27s not a JBoss problem=2C nor a Spring problem=2C=
 but a problem in your own code or in libraries such as DOM4J=2E

For the Introspector=2C the solution (beside not using it)=2C is to have =
a ContextListener that call Introspector=2EflushCaches() when the context=
 is destroyed=2E  Spring provide one=2C it=27s os=2Eweb=2Eutil=2EIntrospe=
ctorCleanupContextListener or something like that=2E Also=2C the leak in =
the Introspector is only an issue for JDK up to JDK 1=2E4=2E2=2C the prob=
lem was corrected in 1=2E5=2E

For the a Driver that wasn=27t unregistered (if your driver class is in W=
EB-INF/lib)=2C the solution is similar=2C you need to have a ContextListe=
ner=2C when the context is destroyed=2C you ask for a list of the registe=
red Drivers from DriverManager=2C and you remove any that comes from your=
 webapp (you can check its ClassLoader)=2E

For the ThreadLocal stuff=2C you have to make sure anything you put in th=
ere you eventually remove it=2E  But if a third party libary does that (e=
=2Eg=2E DOM4J) can you can=27t fix it or have it fixed=2C then it=27s mor=
e complicated to solve=2E  You can look in a previous email from me to th=
is list for a pontential workaround=2C but it=27s kind of a hack=2C and w=
ould be dangerous in production because of concurrency issues=2E

Guillaume


---- Messages d=B4origine ----
De=3A Andy Depue =3Candy=40marathon-man=2Ecom=3E
Date=3A vendredi=2C octobre 22=2C 2004 6=3A25 pm
Objet=3A =5BSpringframework-developer=5D CachedIntrospectionResults leak=3F=


=3E I know this comes up every now and again=2C but I have a leak =

=3E related to Spring=2E  =

=3E I=27m using the latest version of Spring=2C and it appears that =

=3E org=2Espringframework=2Ebeans=2ECachedIntrospectionResults is the =

=3E culprit=2E  =

=3E CachedIntrospectionResults does not use WeakReferences for values =

=3E in the =

=3E =22classCache=22 static WeakHashMap when placing Classes that have =

=3E been loaded =

=3E through the same class loader as the CachedIntrospectionResults=2E  =

=3E I guess it =

=3E assumes that the ClassLoader of the CachedIntrospectionResults =

=3E will be =

=3E garbage collected when the container unloads the app=3F  However=2C i=
n =

=3E my case =

=3E this is not happening=2C and the leaked CachedIntrospectionResults =

=3E instances =

=3E are eating up memory=2E  JBoss 4=2E0 doesn=27t seem to release the Cl=
ass =

=3E (though I =

=3E haven=27t figured out why yet=2E=2E=2E OptimizeIt doesn=27t want to s=
how me =

=3E who is =

=3E holding the reference to the Class itself)=2E  In fact=2C I=27ve noti=
ced =

=3E that =

=3E generally static references (such as =22classCache=22) are not =

=3E released when =

=3E JBoss 4=2E0 unloads an application=2E  Not being any kind of expert o=
n =

=3E class =

=3E loading=2C especially how JBoss does class loading=2C does anyone kno=
w =

=3E what the =

=3E right solution to this issue would be=3F  Is this a JBoss problem=3F =
 =

=3E Is it a =

=3E Spring problem=3F
=3E =

=3E Thanks=2C
=3E  Andy
=3E =

=3E =

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