Slow memory leak in BaseTransaction
Project: JBoss Transaction Manager
Issue Type: Bug
Security Level: Public (Everyone can see)
Components: JTA Implementation
Affects Versions: 4.2.3.SP7
Environment: Windows XP and Solaris, Java 1.5.0_14
Reporter: Andrew McDowell
We had JBossAS running for approximately 4 weeks under extremely heavy load, and reached
an OutOfMemory condition. Heap Dump analysis showed that the class
com.arjuna.ats.internal.jta.transaction.arjunacore.BaseTransaction dominated 85% of the
In the class com.arjuna.ats.internal.jta.transaction.arjunacore.BaseTransaction, there is
a private Hashtable _timeouts, into which a thread id and a timeout value are placed when
transactions are started. However, the entries in the hashtable are never removed, even
if the thread dies. Given all the JBossAS invokers for EJBs create/destroy worker
threads, it means that client transactions can leak approximately 600 bytes (the String,
Integer and Hashtable$Entry).
The _timeouts table in the heap dump had some 6 million entries and a retained heap size
of over 1Gb.
Our workaround to the problem is that we are actively monitoring heap size and performing
rolling restarts when the heap space is too low.
You may want to consider using a ThreadLocal to store the timeout instead of a Hashtable,
which would accomplish the goal of storing the timeout value per thread, but would be
collected if the Thread died, but I will leave implementation speculation to you unless I
find the time to submit a patch.
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