Fix timestamp preservation when extracting cached files #387

cowwoc · 2025-10-05T21:39:01Z

Problem

The Maven Build Cache Extension was not properly preserving file and directory timestamps when restoring attachedOutputs from cache. This caused Maven to warn about files being 'more recent than the packaged artifact' even after running mvnw verify.

Root Causes

CacheUtils.zip() did not store directory entries with their timestamps - only files were added to the ZIP
CacheUtils.unzip() set directory timestamps immediately during extraction, but these timestamps were subsequently overwritten when Files.copy() created files within those directories

Changes

CacheUtils.zip()

Added preVisitDirectory() override to store directory entries in the ZIP with their original timestamps
Modified visitFile() to explicitly set file entry timestamps from BasicFileAttributes

CacheUtils.unzip()

Introduced Map<Path, Long> directoryTimestamps to defer directory timestamp updates
Directory timestamps are now set after all files have been extracted, preventing them from being modified by subsequent file operations
Added HashMap and Map imports to support this functionality

Testing

Created comprehensive test that verifies:

Deep directory structures (a/b/c/)
Directory timestamp preservation
File timestamp preservation
Round-trip zip/unzip consistency

Impact

This fix ensures that cached build outputs maintain their original timestamps, eliminating spurious Maven warnings and improving build cache consistency across multi-module projects.

Fixes timestamp-related warnings like:

[WARNING] File 'formatter/api/target/classes/...' is more recent than the packaged artifact for 'module', please run a full 'mvn package' build

Related Issues and PRs

This PR improves the ZIP archive handling in CacheUtils:

Permissions lost when using attachedOutputs #214 - Permissions lost when using attachedOutputs (similar ZIP limitation concerns)
[MBUILDCACHE-116] Extension fails to regenerate all files in target directory #269 (MBUILDCACHE-116) - Extension fails to regenerate all files in target directory (restoration issues)
[MBUILDCACHE-86] Bugfix and enhancements with the restoration of outputs on disk #318 (MBUILDCACHE-86) - Bugfix and enhancements with restoration of outputs on disk (file restoration improvements)
[MBUILDCACHE-67] Any error in restoring from the cache should resume the non cache build #330 (MBUILDCACHE-67) - Error handling during cache restoration (restoration reliability)
PR [SECURITY] Fix Zip Slip Vulnerability #23 - [SECURITY] Fix Zip Slip Vulnerability (previous security fix in ZIP handling)
PR [MBUILDCACHE-86] bugfix / enhancements restoration of outputs on disk #104 - Original implementation of attachedOutputs restoration

This fix specifically addresses timestamp preservation which was not covered by previous restoration improvements.

olamy · 2025-10-05T22:59:28Z

This caused Maven to warn about files being 'more recent than the packaged artifact' even after running mvnw verify.

how do you have this error?
is it possible to have a test for this change?

AlexanderAshitkin · 2025-10-06T02:02:16Z

feedback provided in #388

Addresses feedback from PR apache#388 review comments and adds comprehensive unit tests to validate timestamp preservation through cache operations. Changes to CacheUtils.java: 1. Implement glob filtering for directory entries - Track directories containing matching files during visitFile() - Only add directory entries in postVisitDirectory() if they contain matching files or no glob filter is active - Preserves glob pattern contract while maintaining timestamp preservation 2. Fix Files.exists() race condition (TOCTOU vulnerability) - Remove unnecessary Files.exists() checks before Files.createDirectories() - Leverage idempotent behavior of createDirectories() - Eliminates time-of-check-to-time-of-use race condition 3. Add error handling for timestamp operations - Wrap Files.setLastModifiedTime() in try-catch blocks - Best-effort timestamp setting with graceful degradation - Prevents failures on filesystems without timestamp support New Unit Tests (CacheUtilsTimestampTest.java): - testFileTimestampPreservation: Verifies file timestamps preserved - testDirectoryTimestampPreservation: Verifies directory timestamps preserved - testDirectoryEntriesStoredInZip: Verifies directories stored in zip - testTimestampsInZipEntries: Verifies zip entry timestamps correct - testMavenWarningScenario: Reproduces Maven warning about file timestamps - testMultipleFilesTimestampConsistency: Verifies consistent timestamps Test Results: - All 6 tests pass with fixes applied - Tests are Java 8 compatible using helper methods - Clear failure messages with timestamp diffs for debugging Fixes apache#387 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>

cowwoc · 2025-10-06T15:51:24Z

@olamy @AlexanderAshitkin Please see the updated commit.

@AlexanderAshitkin Sorry for basing #388 on top of this PR. I have corrected the problem so they are now independent of each other.

@olamy https://github.com/apache/maven-build-cache-extension/pull/387/files#diff-090be5e498346368594f96199eab418ac5486df7368b0825ad1db7f63ef5fff1R214 contains instructions for reproducing the Maven warning message. Please let me know if you are able to reproduce it on your end. Thanks.

elharo · 2025-10-28T11:04:36Z

Can you resolve conflicts and repush?

Copilot

Pull Request Overview

This PR fixes timestamp preservation in the Maven Build Cache Extension to prevent Maven warnings about files being "more recent than the packaged artifact" when restoring outputs from cache.

Key Changes:

Modified CacheUtils.zip() to store directory entries with timestamps in ZIP archives
Updated CacheUtils.unzip() to defer directory timestamp setting until after all files are extracted
Added configuration option preserveTimestamps (default: true) for attached outputs

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
`src/main/java/org/apache/maven/buildcache/CacheUtils.java`	Core fix: Added directory entry handling in zip/unzip with deferred timestamp restoration
`src/main/java/org/apache/maven/buildcache/xml/CacheConfig.java`	Added interface method for `isPreserveTimestamps()` configuration
`src/main/java/org/apache/maven/buildcache/xml/CacheConfigImpl.java`	Implemented `isPreserveTimestamps()` with default value handling
`src/main/java/org/apache/maven/buildcache/CacheControllerImpl.java`	Updated zip/unzip calls to use the new `preserveTimestamps` parameter
`src/main/mdo/build-cache-config.mdo`	Added configuration field for timestamp preservation with documentation
`src/test/java/org/apache/maven/buildcache/CacheUtilsTimestampTest.java`	Comprehensive test suite verifying timestamp preservation behavior
`src/test/java/org/apache/maven/buildcache/ModuleInfoCachingTest.java`	Test ensuring module-info.class files are properly cached

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src/main/java/org/apache/maven/buildcache/CacheUtils.java

src/test/java/org/apache/maven/buildcache/CacheUtilsTimestampTest.java

The build cache extension was not properly preserving file and directory timestamps when restoring attachedOutputs from cache. This caused Maven to warn about files being 'more recent than the packaged artifact' even after a successful build. Root Causes: 1. The zip() method did not store directory entries with timestamps 2. The unzip() method set directory timestamps immediately, but they were later modified by Files.copy() operations for files within Changes: - Modified CacheUtils.zip() to store directory entries with timestamps via preVisitDirectory() callback - Modified CacheUtils.unzip() to defer directory timestamp updates until after all files are extracted, preventing them from being overwritten - Added Map<Path, Long> to track directory timestamps during extraction This ensures that cached build outputs maintain their original timestamps, preventing spurious warnings and improving build cache consistency.

…tion Addresses feedback from PR apache#388 review comments and adds comprehensive testing and configuration capabilities for timestamp preservation. Changes: 1. Fix glob filtering for directory entries (PR apache#388 feedback) - Track directories containing matching files during visitFile() - Only add directory entries in postVisitDirectory() if they contain matching files or no glob filter is active - Preserves glob pattern contract while maintaining timestamp preservation 2. Fix Files.exists() race condition (PR apache#388 feedback) - Remove unnecessary Files.exists() checks before Files.createDirectories() - Leverage idempotent behavior of createDirectories() - Eliminates time-of-check-to-time-of-use (TOCTOU) vulnerability 3. Add error handling for timestamp operations (PR apache#388 feedback) - Wrap Files.setLastModifiedTime() in try-catch blocks - Best-effort timestamp setting with graceful degradation - Prevents failures on filesystems that don't support modification times 4. Add configuration property to control timestamp preservation - New preserveTimestamps field in AttachedOutputs configuration - Default value: true (timestamp preservation enabled by default) - Allows users to disable for performance if needed - Usage: <attachedOutputs><preserveTimestamps>false</preserveTimestamps></attachedOutputs> 5. Add comprehensive unit tests (CacheUtilsTimestampTest.java) - testFileTimestampPreservation: Verifies file timestamps preserved - testDirectoryTimestampPreservation: Verifies directory timestamps preserved - testDirectoryEntriesStoredInZip: Verifies directories stored in zip - testTimestampsInZipEntries: Verifies zip entry timestamps correct - testMavenWarningScenario: Reproduces Maven warning with manual repro steps - testMultipleFilesTimestampConsistency: Verifies consistent timestamps - testPreserveTimestampsFalse: Verifies configuration property works when disabled 6. Add test for module-info.class handling (ModuleInfoCachingTest.java) - Verifies module-info.class is preserved through zip/unzip operations All tests pass (7 tests in CacheUtilsTimestampTest.java).

cowwoc · 2025-10-29T17:31:39Z

Conflicts have been resolved and the branch has been rebased onto the latest master. The PR now includes both timestamp preservation (from this PR) and Unix permission preservation (from master) working together.

- Update exception handling comments to accurately reflect behavior (silently ignore failures rather than logging) - Remove redundant assertEquals in assertTimestampPreserved test method that could never fail

cowwoc force-pushed the fix-timestamp-preservation branch 2 times, most recently from 10eb2c4 to 91e8b9c Compare October 5, 2025 22:20

This was referenced Oct 5, 2025

Permissions lost when using attachedOutputs #214

Closed

[MBUILDCACHE-116] Extension fails to regenerate all files in target directory #269

Open

[MBUILDCACHE-86] Bugfix and enhancements with the restoration of outputs on disk #318

Closed

cowwoc force-pushed the fix-timestamp-preservation branch from 0b0ea6e to 91e8b9c Compare October 6, 2025 15:01

cowwoc force-pushed the fix-timestamp-preservation branch from 0b0ea6e to 7b912ce Compare October 6, 2025 15:10

cowwoc force-pushed the fix-timestamp-preservation branch from 7b912ce to eb1e4da Compare October 6, 2025 15:12

cowwoc force-pushed the fix-timestamp-preservation branch 8 times, most recently from 078171b to 6eee251 Compare October 6, 2025 15:33

cowwoc force-pushed the fix-timestamp-preservation branch 3 times, most recently from 467c204 to d9fc24f Compare October 6, 2025 22:06

AlexanderAshitkin approved these changes Oct 11, 2025

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slachiewicz requested a review from Copilot October 28, 2025 11:27

Copilot AI reviewed Oct 28, 2025

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src/main/java/org/apache/maven/buildcache/CacheUtils.java Show resolved Hide resolved

src/main/java/org/apache/maven/buildcache/CacheUtils.java Outdated Show resolved Hide resolved

src/test/java/org/apache/maven/buildcache/CacheUtilsTimestampTest.java Outdated Show resolved Hide resolved

cowwoc added 2 commits October 29, 2025 13:27

cowwoc force-pushed the fix-timestamp-preservation branch from d9fc24f to 2b4a88f Compare October 29, 2025 17:32

Address GitHub Copilot code review feedback

d634df1

- Update exception handling comments to accurately reflect behavior (silently ignore failures rather than logging) - Remove redundant assertEquals in assertTimestampPreserved test method that could never fail

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Problem

Root Causes

Changes

CacheUtils.zip()

CacheUtils.unzip()

Testing

Impact

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