Fix #12646: project-local-repo clean race condition when root pom has parent - #12650
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Fix #12646: project-local-repo clean race condition when root pom has parent#12650gnodet wants to merge 2 commits into
gnodet wants to merge 2 commits into
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… parent When the root pom.xml has a parent (super-pom) in the reactor, MultiThreadedBuilder schedules the super-pom first, then builds the root pom and sibling modules in parallel. The root pom's clean phase (maven-clean-plugin) deletes the entire target/ directory, which includes project-local-repo. Concurrently, sibling modules that complete successfully write artifacts into target/project-local-repo via ReactorReader.installIntoProjectLocalRepository(). This race causes maven-clean-plugin to fail because the directory is being written to while it tries to delete it. Fix: Add a ReentrantReadWriteLock to ReactorReader that coordinates access to the project-local-repo directory between clean and install operations. When the project whose build directory contains the project-local-repo enters its clean phase, a write lock is acquired to block concurrent installs. The write lock is released when the clean mojo completes (succeeds or fails). Install operations acquire a read lock, allowing multiple concurrent installs but blocking while the owning project's clean is running. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
…e clean race Move the project-local-repo directory from target/project-local-repo to .mvn/project-local-repo so it is not affected by maven-clean-plugin's deletion of target/. This eliminates the race condition in parallel builds where maven-clean-plugin deletes target/ while sibling modules concurrently write artifacts into project-local-repo. The previous lock-based approach prevented crashes but could not guarantee ordering between clean and install operations. Moving the directory outside target/ makes the race structurally impossible — ReactorReader fully owns the lifecycle of project-local-repo (per-GAV cleanup on clean, install on project success). Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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Summary
Move
project-local-repofromtarget/project-local-repoto.mvn/project-local-reposo it is not affected bymaven-clean-plugin's deletion oftarget/.This eliminates the race condition in parallel builds (
mvn clean install -T N) where the root project'smaven-clean-plugindeletestarget/while sibling modules concurrently write artifacts intotarget/project-local-repo.Root cause
In Maven 4,
cleanandinstallphases are placed into the sameTaskSegment, so they execute concurrently across projects in parallel builds. When the rootpom.xmlhas a parent (e.g. a super-pom in the reactor),MultiThreadedBuilderschedules the parent first, then runs the root project and child modules in parallel. The root project's clean phase (viamaven-clean-plugin) races with sibling modules installing artifacts intotarget/project-local-repo.Fix
Move
project-local-repofromtarget/to.mvn/, making it structurally impossible formaven-clean-pluginto interfere.ReactorReaderfully owns the lifecycle:ProjectSucceeded, artifacts are hard-linked (or copied) into.mvn/project-local-repoThis approach is simpler than the previous lock-based fix — the
ReentrantReadWriteLockandisProjectLocalRepoOwner()are removed entirely.Precedent
Storing build-related data outside
target/(survivingclean) is established:~/.m2/.cache/maven-build-cache.gradle/directory at project root (universally gitignored)Trade-off
.mvn/project-local-reposhould be added to.gitignore— similar to how Gradle projects gitignore.gradle/.Fixes #12646
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