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https://issues.apache.org/jira/browse/LUCENE-8162?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16492469#comment-16492469
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Tommaso Teofili commented on LUCENE-8162:
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{quote}but many users index at full speed for a long time and suppressing
merges in that case is dangerous
{quote}
yes, that might make search degrade. To mitigate that the proposed MP has a
maximum number of segments allowed for throttling. So for example if the
throttling algorithm makes the number of segments go beyond a configurable
threshold (e.g. 20), the throttling algorithm doesn't kick in in the next merge
and until the number of segments gets back beyond the threshold.
I have been trying to use [https://github.com/mikemccand/luceneutil] to make
some benchmarks. However it seems the tool only creates one index per
benchmark.
> 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
>
> Attachments: LUCENE-8162.0.patch
>
>
> As discussed in a recent mailing list thread [1] 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 [2].
> That MP doesn'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] : [http://markmail.org/message/re3ifmq2664bqfjk]
> [2] :
> [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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