bug / memory leak in DispatchQueue and EventManager
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Key: CAY-770
URL: https://issues.apache.org/cayenne/browse/CAY-770
Project: Cayenne
Issue Type: Bug
Components: Cayenne Core Library
Affects Versions: 1.2 [STABLE]
Environment: Linux Kernel: 2.16.2
OS: Debian
Tomcat: 5.5.16
Axis: 1.3
Java: Standart Edition 1.5.0_10
Java Args:
-Xms512M
-Xmx1024M
Reporter: Ayhan Kondoz
Assigned To: Andrus Adamchik
Priority: Critical
First a little bit about my setup:
I have 3 servers. Each server runs an axis service. The service uses cayenne
1.2.1 to connect to a database. It reads customer and account information from
the DB etc..
The servers are using cayenne's shared caching with javagroups as the messaging
service so that changes made from one server are dispatched to the other
servers.
The avarage connections per second is somewhere around 4-5 for each server.
However with nearly constant and unchanging usage the load of each server
increases over time.
To further test this I created a test server with a similar setup but
deactivated the shared caching and JavaGroups setup. There I created a test
program that creates totally constant usage of exactly 4 request per second.
Still the load of the server is increasing until the cpu load is so high that
the requests can not be processed anymore.
I installed a java profiler to trying to pinpoint the location of this error
and this is what I found out.
I let the server run for 24 hours and then stopped the program which creates
the test usage.
But even while the server was idle there where still a lot of instances in the
java heap. I even manually started the GC a few times.
java.util.HashMap$Entry (almost 1.5 milion insances)
java.lang.ref.WeakReference (over 1 million insances)
org.objectstyle.cayenne.util.Invocation (over 1 million insances)
org.objectstyle.cayenne.access.DataContext (only 30 Instances)
When the LoadTest is running 58% of the cpu time is used within HashSet.add()
which is called within
org.objectstyle.cayenne.event.DispatchQueue.addInvocation
The longer the test is running the higher the percentage of cpu time used from
addInvocation. The problem seems to be that there are some hard references to
the Invocations objects so that the WeakReferences are not destroyed and the
HashSet gets bigger and bigger.
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