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https://issues.apache.org/jira/browse/LUCENE-8162?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Tommaso Teofili updated LUCENE-8162:
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Description:
As discussed in a [recent mailing list
thread|[http://markmail.org/message/re3ifmq2664bqfjk]] and observed in a
project using Lucene (see OAK-5192 and OAK-6710), it is sometimes helpful to
throttle the aggressiveness of (Tiered)MergePolicy when commit rate is high.
In the case of Apache Jackrabbit Oak a dedicated {{MergePolicy}} was
implemented [1].
That MP didn't merge in case the number of segments is below a certain
threshold (e.g. 30) and commit rate (docs per sec and MB per sec) is high (e.g.
above 1000 doc / sec , 5MB / sec).
In such impl, the commit rate thresholds adapt to average commit rate by means
of single exponential smoothing.
The results in that specific case looked encouraging as it brought a 5% perf
improvement in querying and ~10% reduced IO. However Oak has some specifics
which might not fit in other scenarios. Anyway it could be interesting to see
how this behaves in plain Lucene scenario.
[1] :
[https://github.com/apache/jackrabbit-oak/blob/trunk/oak-lucene/src/main/java/org/apache/jackrabbit/oak/plugins/index/lucene/writer/CommitMitigatingTieredMergePolicy.java]
was:
As discussed in a [recent mailing list
thread|[http://markmail.org/message/re3ifmq2664bqfjk],]] and observed in a
project using Lucene (see OAK-5192 and OAK-6710), it is sometimes helpful to
throttle the aggressiveness of (Tiered)MergePolicy when commit rate is high.
In the case of Apache Jackrabbit Oak a dedicated {{MergePolicy}} was
implemented [1].
That MP didn't merge in case the number of segments is below a certain
threshold (e.g. 30) and commit rate (docs per sec and MB per sec) is high (e.g.
above 1000 doc / sec , 5MB / sec).
In such impl, the commit rate thresholds adapt to average commit rate by means
of single exponential smoothing.
The results in that specific case looked encouraging as it brought a 5% perf
improvement in querying and ~10% reduced IO. However Oak has some specifics
which might not fit in other scenarios. Anyway it could be interesting to see
how this behaves in plain Lucene scenario.
[1] :
[https://github.com/apache/jackrabbit-oak/blob/trunk/oak-lucene/src/main/java/org/apache/jackrabbit/oak/plugins/index/lucene/writer/CommitMitigatingTieredMergePolicy.java]
> Make it possible to throttle (Tiered)MergePolicy when commit rate is high
> -------------------------------------------------------------------------
>
> Key: LUCENE-8162
> URL: https://issues.apache.org/jira/browse/LUCENE-8162
> Project: Lucene - Core
> Issue Type: Improvement
> Components: core/index
> Reporter: Tommaso Teofili
> Priority: Major
> Fix For: trunk
>
>
> As discussed in a [recent mailing list
> thread|[http://markmail.org/message/re3ifmq2664bqfjk]] and observed in a
> project using Lucene (see OAK-5192 and OAK-6710), it is sometimes helpful to
> throttle the aggressiveness of (Tiered)MergePolicy when commit rate is high.
> In the case of Apache Jackrabbit Oak a dedicated {{MergePolicy}} was
> implemented [1].
> That MP didn't merge in case the number of segments is below a certain
> threshold (e.g. 30) and commit rate (docs per sec and MB per sec) is high
> (e.g. above 1000 doc / sec , 5MB / sec).
> In such impl, the commit rate thresholds adapt to average commit rate by
> means of single exponential smoothing.
> The results in that specific case looked encouraging as it brought a 5% perf
> improvement in querying and ~10% reduced IO. However Oak has some specifics
> which might not fit in other scenarios. Anyway it could be interesting to see
> how this behaves in plain Lucene scenario.
> [1] :
> [https://github.com/apache/jackrabbit-oak/blob/trunk/oak-lucene/src/main/java/org/apache/jackrabbit/oak/plugins/index/lucene/writer/CommitMitigatingTieredMergePolicy.java]
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