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https://issues.apache.org/jira/browse/RATIS-2063?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17841800#comment-17841800
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Janus Chow commented on RATIS-2063:
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Hello, [~duongnguyen], I saw it's already unregistered
[here|https://github.com/apache/ratis/blob/b0ec1143c49e61525baf5da935a3509a59246883/ratis-server/src/main/java/org/apache/ratis/server/raftlog/segmented/SegmentedRaftLog.java#L572]
. Am I missing anything?
> Unclosed SegmentedRaftLogMetrics causes memory leaks.
> -----------------------------------------------------
>
> Key: RATIS-2063
> URL: https://issues.apache.org/jira/browse/RATIS-2063
> Project: Ratis
> Issue Type: Improvement
> Reporter: Duong
> Priority: Major
>
> [SegmentedRaftLogMetrics|https://github.com/duongkame/ratis/blob/master/ratis-server/src/main/java/org/apache/ratis/server/raftlog/segmented/SegmentedRaftLog.java#L212-L212]
> is not unregistered when RaftServer is closed. This causes the leak of many
> objects that SegmentedRaftLogMetrics refers to indirectly via a metric
> register, for example, SegmentedRaftLog:
> {code:java}
> SegmentedRaftLogWorker(RaftGroupMemberId memberId, StateMachine
> stateMachine, Runnable submitUpdateCommitEvent,
> RaftServer.Division server, RaftStorage storage,
> RaftProperties properties,
> SegmentedRaftLogMetrics metricRegistry) {
> metricRegistry.addDataQueueSizeGauge(queue::getNumElements);
> metricRegistry.addLogWorkerQueueSizeGauge(writeTasks.q::size);
> metricRegistry.addFlushBatchSizeGauge(() -> flushBatchSize);
> }
> {code}
> In the above code, MetricRegistry will keep references to the lamda objects
> which in turn refer to the SegmentedRaftLogWorker object itself.
> The metricRegistry in SegmentedRaftLogMetrics must be unregistered when
> RaftServer is close to allowing GC to collect all discarded objects.
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