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https://issues.apache.org/jira/browse/CASSANDRA-16161?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17224483#comment-17224483
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Michael Semb Wever edited comment on CASSANDRA-16161 at 11/2/20, 8:12 AM:
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bq. This could almost be classified as a bug. In conf/cassandra.yaml it states
for compaction_throughput_mb_per_sec: "Note that this account for all types of
compaction, including validation compaction"
I am keen on making this a bug and throttling validation compactions under
{{compaction_throughput_mb_per_sec}}, as the existing documentation says it
already does. But have some questions, like some of the past discussion in
CASSANDRA-3635. There are differences between clusters on how validation and
normal compactions interact, also with each using resources differently:
validations use more cpu and only read IO compared to normal compactions.
If validation compactions are made to honour
{{compaction_throughput_mb_per_sec}}, what impact might that have on existing
clusters? (particularly those unsuspecting to such a change in a patch
upgrade). If there are users that are dependent on validation compactions being
unthrottled and completing faster than other compactions, how would they
achieve that after this change?
was (Author: michaelsembwever):
bq. This could almost be classified as a bug. In conf/cassandra.yaml it states
for compaction_throughput_mb_per_sec: "Note that this account for all types of
compaction, including validation compaction"
I am keen on making this a bug and throttling validation compactions under
{{compaction_throughput_mb_per_sec}}, as the existing documentation says it
already does. But have some questions, like some of the past discussion in
CASSANDRA-3635. There are differences between clusters on how validation and
normal compactions interact, with each using resources differently: validations
use more cpu and only read IO compared to normal compactions.
If validation compactions are made to honour
{{compaction_throughput_mb_per_sec}}, what impact might that have on existing
clusters? (particularly those unsuspecting to such a change in a patch
upgrade). If there are users that are dependent on validation compactions being
unthrottled and completing faster than other compactions, how would they
achieve that after this change?
> Validation Compactions causing Java GC pressure
> -----------------------------------------------
>
> Key: CASSANDRA-16161
> URL: https://issues.apache.org/jira/browse/CASSANDRA-16161
> Project: Cassandra
> Issue Type: Improvement
> Components: Local/Compaction, Local/Config, Tool/nodetool
> Reporter: Cameron Zemek
> Assignee: Stefan Miklosovic
> Priority: Normal
> Fix For: 3.11.x, 3.11.8
>
> Attachments: 16161.patch
>
>
> Validation Compactions are not rate limited which can cause Java GC pressure
> and result in spikes in latency.
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