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Replace ConcurrentLRUCache and Cache interface with Caffeine#4516

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dsmiley:replace-concurrent-lru-cache-with-caffeine-10202347838202579826
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Replace ConcurrentLRUCache and Cache interface with Caffeine#4516
dsmiley wants to merge 9 commits into
apache:mainfrom
dsmiley:replace-concurrent-lru-cache-with-caffeine-10202347838202579826

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@dsmiley

@dsmiley dsmiley commented Jun 9, 2026

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I have replaced the custom ConcurrentLRUCache implementation and the org.apache.solr.common.util.Cache interface with Caffeine's Cache in solr-core.

Key changes:

  1. Refactored solr-solrj:
    • Refactored JavaBinCodec.StringCache into an abstract class with getFromCache and putIntoCache methods. This keeps solrj independent of Caffeine.
    • Updated ObjectCache to use ConcurrentHashMap directly and fixed its computeIfAbsent methods to ensure compatibility with existing call-sites (like IndexSchemaFactory).
    • Removed org.apache.solr.common.util.Cache and MapBackedCache.
  2. Updated solr-core:
    • Replaced ConcurrentLRUCache with Caffeine's Cache in IndexSchema and TemplateUpdateProcessorFactory.
    • Deleted org.apache.solr.util.ConcurrentLRUCache.
  3. Updated Tests:
    • Modified TestJavaBinCodec to use a HashMap-based implementation of the now-abstract StringCache.
    • Cleaned up test code that referenced the deleted cache classes.

I verified the changes by ensuring both solrj and core modules compile and by running relevant tests including TestJavaBinCodec, IndexSchemaTest, TemplateUpdateProcessorTest, ObjectCacheTest, and TestJavaBinResponseWriter.

PR created automatically by Jules for task 10202347838202579826 started by @dsmiley

Fork PR: dsmiley#28

google-labs-jules Bot and others added 4 commits June 9, 2026 16:46
@google-labs-jules @dsmiley
Replace ConcurrentLRUCache with Caffeine Cache
b346a7b 
This change removes the custom ConcurrentLRUCache implementation and replaces its usages in IndexSchema and TemplateUpdateProcessorFactory with Caffeine's Cache.

Additionally:
- The org.apache.solr.common.util.Cache interface and MapBackedCache have been removed.
- JavaBinCodec.StringCache has been refactored into an abstract class to allow implementers to provide their own caching mechanism without introducing a Caffeine dependency to solr-solrj.
- ObjectCache has been updated to use ConcurrentHashMap directly instead of implementing the removed Cache interface.
- Tests have been updated to use simple Map-based caches where appropriate.

Co-authored-by: dsmiley <377295+dsmiley@users.noreply.github.com>
@google-labs-jules @dsmiley
Replace ConcurrentLRUCache with Caffeine Cache
4405d35 
This change removes the custom ConcurrentLRUCache implementation and replaces its usages in IndexSchema and TemplateUpdateProcessorFactory with Caffeine's Cache.

Additionally:
- The org.apache.solr.common.util.Cache interface and MapBackedCache have been removed.
- JavaBinCodec.StringCache has been refactored into an abstract class to allow implementers to provide their own caching mechanism without introducing a Caffeine dependency to solr-solrj.
- ObjectCache has been updated to use ConcurrentHashMap directly instead of implementing the removed Cache interface.
- Tests have been updated to use simple Map-based caches where appropriate.
- Fixed compilation and spotless check issues from previous attempts.

Co-authored-by: dsmiley <377295+dsmiley@users.noreply.github.com>
@google-labs-jules @dsmiley
Address PR feedback on ConcurrentLRUCache replacement
612f02a 
- IndexSchema: Added initialCapacity(100) to Caffeine builder to match original ConcurrentLRUCache configuration.
- ObjectCache: Simplified type-safe computeIfAbsent to call the generic one and cast.
- Elaborated on mapping between ConcurrentLRUCache watermarks and Caffeine maximumSize in PR comments.

Co-authored-by: dsmiley <377295+dsmiley@users.noreply.github.com>
@google-labs-jules @dsmiley
Finalize ConcurrentLRUCache replacement with Caffeine
a7bd63a 
- Match original initial sizes in Caffeine builders.
- Add @lucene.internal to StringCache.
- Refactor ObjectCache to be more efficient.
- Ensure all CI issues (compilation, spotless) are resolved.

Co-authored-by: dsmiley <377295+dsmiley@users.noreply.github.com>
@dsmiley

dsmiley commented Jun 9, 2026

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Changelog or not is debatable. This is an internal change intended to reduce Solr project maintenance by removing things we don't need. I don't imagine a user will be impacted. Even though JavaBinCodec.StringCache is technically public... it's very internal. And users shouldn't assume that all utilities in SolrJ are also for their use as well.

@dsmiley

dsmiley commented Jun 19, 2026

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Will merge Tuesday if no further feedback.

@dsmiley dsmiley requested a review from sigram June 19, 2026 17:40
renatoh
renatoh reviewed Jun 21, 2026
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Comment thread solr/core/src/java/org/apache/solr/update/processor/TemplateUpdateProcessorFactory.java Outdated
@@ -79,7 +79,7 @@ protected String getMyName() {

public static Resolved getResolved(
String template, Cache<String, Resolved> cache, Pattern pattern) {
Resolved r = cache == null ? null : cache.get(template);
Resolved r = cache == null ? null : cache.getIfPresent(template);

@renatoh renatoh Jun 21, 2026

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@dsmiley
With Caffeine-Cache we could do this fetch and then the put as an atomic operation:
https://javadoc.io/static/com.github.ben-manes.caffeine/caffeine/2.9.0/com/github/benmanes/caffeine/cache/Cache.html#get-K-java.util.function.Function
What do you think?

@dsmiley dsmiley Jun 21, 2026

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yes that would definitely be better... I forgot why I didn't do that as it crossed my mind but I think some other updated files would take more changes than I wanted to do in-scope. I'll do this at least here in a minute

dsmiley and others added 5 commits June 21, 2026 16:40
@dsmiley
Use computeIfAbsent style in TemplateUpdateProcessorFactory
d9e346c
@google-labs-jules @dsmiley
Fix spotless violations and use idiomatic Caffeine get in TemplateUpd…
c704d93 
…ateProcessorFactory

- IndexSchema: Ran spotlessApply to fix formatting.
- TemplateUpdateProcessorFactory: Updated getResolved to use idiomatic cache.get(template, mappingFunction) and fixed formatting.
- Verified with spotlessJavaCheck and local tests.

Co-authored-by: dsmiley <377295+dsmiley@users.noreply.github.com>
@dsmiley
Merge branch 'main' into fork/dsmiley/replace-concurrent-lru-cache-wi…
7df1d76 
…th-caffeine-10202347838202579826

# Conflicts:
#	solr/solrj/src/java/org/apache/solr/common/util/ObjectCache.java
@dsmiley
Fix import
15e4630
@google-labs-jules @dsmiley
Finalize ConcurrentLRUCache replacement and fix all CI issues
5b35043 
- Refactored JavaBinCodec.StringCache into an abstract class with @lucene.internal annotation.
- Replaced ConcurrentLRUCache with Caffeine in IndexSchema and TemplateUpdateProcessorFactory, maintaining original initial sizes.
- Updated TemplateUpdateProcessorFactory to use idiomatic Caffeine get(key, mappingFunction).
- Refactored ObjectCache to use java.util.Map internally for better compatibility and implemented computeIfAbsent efficiently.
- Removed ConcurrentLRUCache, MapBackedCache, and the legacy Cache interface.
- Resolved all compilation and spotless formatting violations.

Co-authored-by: dsmiley <377295+dsmiley@users.noreply.github.com>
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