Alex Rudyy created QPID-8384:
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Summary: [Broker-J] LastValueQueueList can leak deleted queue
entries
Key: QPID-8384
URL: https://issues.apache.org/jira/browse/QPID-8384
Project: Qpid
Issue Type: Task
Components: Broker-J
Affects Versions: qpid-java-broker-7.1.4, qpid-java-broker-7.1.3,
qpid-java-broker-7.0.8, qpid-java-broker-7.1.2, qpid-java-broker-7.1.1,
qpid-java-broker-7.0.7, qpid-java-broker-7.0.6, qpid-java-broker-7.0.5,
qpid-java-broker-7.0.4, qpid-java-broker-7.1.0, qpid-java-6.1.7,
qpid-java-broker-7.0.1, qpid-java-6.1.5, qpid-java-broker-7.0.0,
qpid-java-6.1.4, qpid-java-6.0.8, qpid-java-6.1.3, qpid-java-6.0.7,
qpid-java-6.1.2, qpid-java-6.1.1, qpid-java-6.0.6, qpid-java-6.1,
qpid-java-6.0.5, qpid-java-6.0.4, qpid-java-6.0.3, qpid-java-6.0.2,
qpid-java-6.0.1, qpid-java-6.0, 0.32, 0.31, 0.30, 0.29, 0.28, 0.27, 0.26, 0.25,
0.24, 0.23, 0.22, 0.21, 0.20, 0.19, 0.18, 0.17, qpid-java-6.1.8
Reporter: Alex Rudyy
Fix For: qpid-java-broker-7.1.6
Qpid Broker-j can run out of heap memory due to leaking deleted LVQ entries
via {{LastValueQueueList#_latestValuesMap}}.
The deleted queue entry can be left in {{LastValueQueueList#_latestValuesMap}}
in result of race between enqueing thread and consuming or management thread,
where entry is deleted. An LVQ entry is removed from
{{LastValueQueueList#_latestValuesMap}}, when {{_latestValueReference}} is set
on the entry as part of invocation {{LastValueQueueList#add(...)}}. If
{{_latestValueReference}} is not set in result of unfortunate thread
scheduling, the LVQ entry might not be removed from the
{{LastValueQueueList#_latestValuesMap}} as part of invocation of
{{LastValueQueueList$ConflationQueueEntry#onDelete}}.
In some unlucky circumstances the deleted entry can hold a reference to another
deleted entry. They can makes a chain of deleted entries, which is referenced
from {{LastValueQueueList#_latestValuesMap}}. The latter prevents the Garbage
Collector from freeing the memory occupied by the chain of deleted entries.
The solution for this problem seems require adding into
{{LastValueQueueList#add(...)}} after setting of
{{LastValueQueueList$ConflationQueueEntry#_latestValueReference}} a call to
{{LastValueQueueList$ConflationQueueEntry#onDelete}}, when the entry state is
{{DELETED}}.
The reason why deleted LVQ entries remained linked together is not clear yet.
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