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https://issues.apache.org/jira/browse/CASSANDRA-13929?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16347629#comment-16347629
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Nate McCall commented on CASSANDRA-13929:
-----------------------------------------
If [~norman] is around, would be great to get his input on whether this might
be a leak or tuning issue with recycler. Thanks for your patience and
willingness to test this out [~tsteinmaurer].
> BTree$Builder / io.netty.util.Recycler$Stack leaking memory
> -----------------------------------------------------------
>
> Key: CASSANDRA-13929
> URL: https://issues.apache.org/jira/browse/CASSANDRA-13929
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Reporter: Thomas Steinmaurer
> Priority: Major
> Fix For: 3.11.x
>
> Attachments: cassandra_3.11.0_min_memory_utilization.jpg,
> cassandra_3.11.1_NORECYCLE_memory_utilization.jpg,
> cassandra_3.11.1_mat_dominator_classes.png,
> cassandra_3.11.1_mat_dominator_classes_FIXED.png,
> cassandra_3.11.1_snapshot_heaputilization.png
>
>
> Different to CASSANDRA-13754, there seems to be another memory leak in
> 3.11.0+ in BTree$Builder / io.netty.util.Recycler$Stack.
> * heap utilization increase after upgrading to 3.11.0 =>
> cassandra_3.11.0_min_memory_utilization.jpg
> * No difference after upgrading to 3.11.1 (snapshot build) =>
> cassandra_3.11.1_snapshot_heaputilization.png; thus most likely after fixing
> CASSANDRA-13754, more visible now
> * MAT shows io.netty.util.Recycler$Stack as top contributing class =>
> cassandra_3.11.1_mat_dominator_classes.png
> * With -Xmx8G (CMS) and our load pattern, we have to do a rolling restart
> after ~ 72 hours
> Verified the following fix, namely explicitly unreferencing the
> _recycleHandle_ member (making it non-final). In
> _org.apache.cassandra.utils.btree.BTree.Builder.recycle()_
> {code}
> public void recycle()
> {
> if (recycleHandle != null)
> {
> this.cleanup();
> builderRecycler.recycle(this, recycleHandle);
> recycleHandle = null; // ADDED
> }
> }
> {code}
> Patched a single node in our loadtest cluster with this change and after ~ 10
> hours uptime, no sign of the previously offending class in MAT anymore =>
> cassandra_3.11.1_mat_dominator_classes_FIXED.png
> Can' say if this has any other side effects etc., but I doubt.
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