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Posted to issues@lucene.apache.org by "Andrzej Bialecki (Jira)" <ji...@apache.org> on 2019/11/06 20:14:00 UTC
[jira] [Commented] (SOLR-13898) Non-atomic use of SolrCache get /
put
[ https://issues.apache.org/jira/browse/SOLR-13898?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16968661#comment-16968661 ]
Andrzej Bialecki commented on SOLR-13898:
-----------------------------------------
Initial patch:
* I added {{SolrCache.computeIfAbsent}} method and implemented it in each subclass.
* {{UninvertedField}} and {{SolrDocumentFetcher}} (plus a few other minor use cases) have been changed to use {{computeIfAbsent}}. However, the way caching is used in {{SolrIndexSearcher}} was too scary for me to touch ... so this still needs to be modified.
* I'd like to add some performance tests to see how the hit ratio is affected by concurrent initialization when using get / put vs. computeIfAbsent.
All existing tests are passing.
> Non-atomic use of SolrCache get / put
> -------------------------------------
>
> Key: SOLR-13898
> URL: https://issues.apache.org/jira/browse/SOLR-13898
> Project: Solr
> Issue Type: Bug
> Security Level: Public(Default Security Level. Issues are Public)
> Affects Versions: 8.3
> Reporter: Andrzej Bialecki
> Assignee: Andrzej Bialecki
> Priority: Major
> Attachments: SOLR-13898.patch
>
>
> As pointed out by [~ben.manes] in SOLR-13817 Solr code base in many key places uses a similar pattern of non-atomic get / put calls to SolrCache-s. In multi-threaded environment this leads to cache misses and additional unnecessary computations when competing threads both discover a missing value, non-atomically compute it and update the cache.
> Some of these places are known performance bottlenecks where efficient caching is especially important, such as {{SolrIndexSearcher}}, {{SolrDocumentFetcher}}, {{UninvertedField}} and join queries .
> I propose to add {{SolrCache.computeIfAbsent(key, mappingFunction)}} that will atomically retrieve existing values or compute and update the cache. This will require also changing how the {{SolrCache.get(...)}} is used in many components.
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