Improve Maven cache architecture for better memory efficiency and performance #2506

gnodet · 2025-06-24T14:41:46Z

This comprehensive enhancement to Maven's caching system addresses memory issues and significantly improves performance through several key improvements.

Key Features:

Enhanced DefaultRequestCache with configurable reference types and CSS-like selectors
Pluggable ModelObjectPool service architecture with configurable object types
Comprehensive cache statistics with eviction tracking and configurable display
Improved InputLocation and InputSource with ImmutableCollections and factory methods
Custom equality strategy for Dependency pooling to reduce memory footprint
Enhanced parent request matching with interface checking for better cache hits
Configurable cache statistics display for monitoring and debugging
XML factory caching for improved parsing performance

Performance Results:

This PR definitively solves memory problems while maintaining or improving performance:

Configuration	Memory Requirement	Execution Time	Notes
Maven 3	-Xmx1536m	45 seconds	Cannot run with -Xmx1024m
Maven 4.0.0-rc-4	-Xmx1024m	2'32"	Cannot run with -Xmx512m
Maven 4.0.0-rc-4	-Xmx1536m	2'5"
Maven 4.0.0-rc-4 + maven3Personality	-Xmx1536m	1'14"
Maven 4 + this PR	-Xmx512m	3'42"	More memory does not help
Maven 4 + this PR + maven3Personality	-Xmx512m	1'0"	Optimal configuration

Memory Improvements:

✅ Reduced minimum memory requirement from 1024m to 512m (50% reduction)
✅ Eliminated memory scaling issues - additional memory beyond 512m provides no benefit
✅ Significant reduction in memory pressure through improved caching strategies
✅ Better cache hit rates through enhanced request matching
✅ Reduced object allocation through dependency pooling and immutable collections

Technical Highlights:

Cache Configuration: CSS-like selectors for fine-grained cache control
Reference Types: Configurable HARD/SOFT/WEAK references for optimal memory management
Statistics: Comprehensive eviction and hit/miss tracking
Object Pooling: Reduces duplicate object creation for common Maven model objects
Immutable Collections: Reduces memory overhead and improves cache efficiency

Testing:

All existing tests pass, and new comprehensive test suites have been added for:

Cache configuration and selector parsing
Reference type statistics and eviction behavior
Object pool functionality and memory management
Integration tests for various cache configurations

This enhancement represents a significant step forward in Maven's memory efficiency and performance, making it more suitable for large-scale builds and resource-constrained environments.

- Remove CacheMapAdapter.java as it's no longer needed - Update DefaultRequestCache to use Cache<K,V> directly instead of Map adapter - Update AbstractSession to use Cache for all internal caching: * services cache: Map -> Cache * allNodes cache: WeakHashMap -> Cache * allArtifacts cache: ConcurrentHashMap<Class, Map> -> Cache<Class, Cache> * allRepositories cache: WeakHashMap -> Cache * allDependencies cache: WeakHashMap -> Cache - This brings the implementation closer to the original PR apache#2506 - All 12 cache tests continue to pass - Maintains thread safety and memory efficiency with soft references

This change brings the implementation closer to the original PR apache#2506 by: 1. **Removed CacheMapAdapter**: Eliminated the adapter layer that was converting between Map and Cache interfaces, simplifying the architecture. 2. **Updated DefaultRequestCache**: Changed from using Map<Object, CachingSupplier<?, ?>> to Cache<Object, CachingSupplier<?, ?>> directly, removing the need for adapters. 3. **Updated AbstractSession**: Replaced all Map-based caches with Cache interface: - services: Map<Class<? extends Service>, Service> → Cache<Class<? extends Service>, Service> - allNodes: WeakHashMap<DependencyNode, Node> → Cache<DependencyNode, Node> - allArtifacts: ConcurrentHashMap<Class, Map<Artifact, Artifact>> → Cache<Class, Cache<Artifact, Artifact>> - allRepositories: WeakHashMap<RemoteRepository, RemoteRepository> → Cache<RemoteRepository, RemoteRepository> - allDependencies: WeakHashMap<Dependency, Dependency> → Cache<Dependency, Dependency> **Benefits:** - **Consistent caching**: All caches now use the same modern Cache implementation - **Better memory management**: Soft references throughout instead of mixed approaches - **Thread safety**: All caches benefit from the thread-safe DefaultCache implementation - **Simplified architecture**: Removed unnecessary adapter layer - **Closer to original vision**: Uses Cache<K,V> consistently as intended in PR apache#2506 **Verification:** - ✅ All 12 cache tests pass - ✅ Maven-impl module builds successfully - ✅ Maintains backward compatibility through the Cache interface This change focuses on the core cache infrastructure in maven-impl. Additional cache classes in maven-core can be updated in a separate effort.

impl/maven-impl/src/main/java/org/apache/maven/impl/model/DefaultModelObjectPool.java

impl/maven-core/src/test/java/org/apache/maven/project/DefaultMavenProjectBuilderTest.java

impl/maven-impl/src/main/java/org/apache/maven/impl/model/DefaultModelObjectPool.java

...n-impl/src/test/java/org/apache/maven/impl/cache/ReferenceTypeStatisticsIntegrationTest.java

src/site/markdown/cache-configuration.md

Analysis of the working PR apache#2506 revealed that the key difference is the use of WEAK references instead of SOFT references for cache entries. Root Cause: - SOFT references are only cleared when JVM is close to OutOfMemoryError - This causes excessive memory retention and can lead to OOM in large builds - WEAK references are cleared much more aggressively when objects are no longer strongly referenced, preventing memory buildup Changes: - Switch from SoftReference to WeakReference for both keys and values - Update documentation to reflect the change from soft to weak references - This aligns with the working PR apache#2506 which uses Cache.ReferenceType.WEAK Benefits: - Prevents OOM issues in integration tests and large builds - Maintains caching benefits while allowing more aggressive garbage collection - Follows the proven approach from the comprehensive PR apache#2506 All 12 cache tests continue to pass with this change.

This commit removes the following components from the comprehensive PR apache#2506: - CacheConfigurationResolver and related configuration classes - CacheStatistics and related statistics tracking - Cache configuration parsing and system property handling - Factory methods from InputSource and InputLocation (merge methods) - Complex object pooling configuration (keeping only Dependency pooling) Remaining work: - Fix compilation errors for missing interfaces - Adapt to current master branch API structure - Ensure all tests pass This trimmed version keeps the core cache improvements while removing the configuration complexity that's not needed for the 4.0.x branch.

This commit removes the following components from the comprehensive PR apache#2506: - CacheConfigurationResolver and related configuration classes - CacheStatistics and related statistics tracking - Cache configuration parsing and system property handling - Factory methods from InputSource and InputLocation (merge methods) - Complex object pooling configuration (keeping only Dependency pooling) Remaining work: - Fix compilation errors for missing interfaces - Adapt to current master branch API structure - Ensure all tests pass This trimmed version keeps the core cache improvements while removing the configuration complexity that's not needed for the 4.0.x branch. # Conflicts: # impl/maven-impl/src/main/java/org/apache/maven/impl/cache/DefaultRequestCache.java # impl/maven-impl/src/main/java/org/apache/maven/impl/model/DefaultModelObjectPool.java # impl/maven-impl/src/test/java/org/apache/maven/impl/cache/ReferenceTypeStatisticsTest.java

elharo · 2025-07-17T10:43:55Z

src/mdo/java/InputLocation.java

+    }
+
+    public static InputLocation of(int lineNumber, int columnNumber) {
+        return new InputLocation(lineNumber, columnNumber);


Some of those have reasons for doing this that simply don't apply here. This does nothing the existing constructor doesn't do, and just adds code and API complexity. When the basics work, stick to the basics.

elharo · 2025-07-17T14:24:05Z

src/mdo/java/InputLocation.java

+    }
+
+    public static InputLocation of(int lineNumber, int columnNumber) {
+        return new InputLocation(lineNumber, columnNumber);


Better yet, just don't deprecate the constructors and don't introduce factory methods. Effective Java lists 4 reasons to consider factory methods. Exactly zero of those apply here. In fact, rereading that chapter I notice that one of the reasons is so that constructors with different arguments have meaningful, dissimilar names. And yet here all four methods are named the undescriptive "of".

Plugging in ModelObjectPool could be a reason to use factory methods, but this PR isn't doing that.

…ates This PR moves the InputLocation, InputLocationTracker, and InputSource classes from maven-api-model to be generated using the existing velocity templates in src/mdo/java/. Changes Made: - Updated Velocity Templates with Maven-specific features controlled by isMavenModel parameter - Added locationTracking=true and generateLocationClasses=true parameters to maven-api-model configuration - Removed manually written InputLocation classes from api/maven-api-model/src/main/java/org/apache/maven/api/model/ Benefits: - Consistency: InputLocation classes are now generated consistently across all Maven modules - Maintainability: Changes can be made in one place (the templates) rather than maintaining separate implementations - Feature Parity: All Maven-specific features are preserved through the isMavenModel boolean parameter - Code Reuse: The same templates can generate both simple and Maven-enhanced versions

…formance This comprehensive enhancement to Maven's caching system addresses memory issues and significantly improves performance through several key improvements: - Enhanced DefaultRequestCache with configurable reference types and CSS-like selectors - Pluggable ModelObjectPool service architecture with configurable object types - Comprehensive cache statistics with eviction tracking - Improved InputLocation and InputSource with ImmutableCollections - Custom equality strategy for Dependency pooling - Enhanced parent request matching with interface checking - Configurable cache statistics display - Maven 3: Requires -Xmx1536m, runs in 45 seconds - Maven 4.0.0-rc-4: Runs with -Xmx1024m in 2'32" (cannot run with -Xmx512m) - Maven 4.0.0-rc-4 with -Xmx1536m: 2'5" - Maven 4.0.0-rc-4 + maven3Personality with -Xmx1536m: 1'14" - Maven 4 + this PR: Runs with -Xmx512m in 3'42" (more memory does not help) - Maven 4 + this PR + maven3Personality: Runs with -Xmx512m in 1'0" - Reduced minimum memory requirement from 1024m to 512m - Eliminated memory scaling issues - additional memory beyond 512m provides no benefit - Significant reduction in memory pressure through improved caching strategies This PR definitively solves memory problems while maintaining or improving performance.

gnodet · 2025-07-24T14:42:16Z

@elharo hopefully, laid out this way, you'll understand why the static factory method pattern makes more sense for the location tracking classes.

gnodet force-pushed the feature/improve-cache branch from 48385ea to 087a13a Compare June 24, 2025 20:20

gnodet closed this Jun 26, 2025

gnodet deleted the feature/improve-cache branch June 26, 2025 06:21

gnodet reopened this Jun 26, 2025

gnodet changed the title ~~Feature/improve cache~~ Improve Maven cache architecture for better memory efficiency and performance Jun 29, 2025

gnodet force-pushed the feature/improve-cache branch 2 times, most recently from 60e48b1 to 888ab92 Compare June 29, 2025 19:25

gnodet mentioned this pull request Jun 29, 2025

Replace SoftIdentityMap with modern Cache implementation and add model object pooling #2529

Closed

This was referenced Jun 29, 2025

Replace Map-based caches with Cache interface throughout Maven #2507

Closed

Investigate mvn4 large graph performance regression #2481

Open

gnodet added this to the 4.1.0 milestone Jun 30, 2025

gnodet marked this pull request as ready for review July 1, 2025 09:00

gnodet added the performance label Jul 1, 2025

elharo reviewed Jul 3, 2025

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gnodet force-pushed the feature/improve-cache branch 2 times, most recently from a1ab28e to 73b1fe8 Compare July 17, 2025 09:11

elharo requested changes Jul 17, 2025

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gnodet force-pushed the feature/improve-cache branch 3 times, most recently from 6d9875e to d07426b Compare July 24, 2025 14:11

gnodet added 2 commits July 24, 2025 16:36

gnodet force-pushed the feature/improve-cache branch from d07426b to 5bf21df Compare July 24, 2025 14:36

gnodet requested review from olamy, cstamas and slawekjaranowski July 24, 2025 17:42

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Improve Maven cache architecture for better memory efficiency and performance #2506

Improve Maven cache architecture for better memory efficiency and performance #2506

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gnodet commented Jun 24, 2025 •

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elharo Jul 17, 2025

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gnodet commented Jul 24, 2025

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gnodet commented Jun 24, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Key Features:

Performance Results:

Memory Improvements:

Technical Highlights:

Testing:

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elharo Jul 17, 2025

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