From 047b71588fe4c5bb45f628433a481299919b9c79 Mon Sep 17 00:00:00 2001 From: Guillaume Nodet Date: Fri, 31 Jul 2026 15:51:05 +0200 Subject: [PATCH 1/2] Fix #12646: project-local-repo clean race condition when root pom has 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 --- .../java/org/apache/maven/ReactorReader.java | 43 +++++++++++++- ...Tgh12646ProjectLocalRepoCleanRaceTest.java | 59 +++++++++++++++++++ .../.mvn/.gitkeep | 0 .../module-a/pom.xml | 29 +++++++++ .../module-a/src/main/java/a/A.java | 7 +++ .../module-b/pom.xml | 29 +++++++++ .../module-b/src/main/java/b/B.java | 7 +++ .../module-c/pom.xml | 29 +++++++++ .../module-c/src/main/java/c/C.java | 7 +++ .../module-d/pom.xml | 29 +++++++++ .../module-d/src/main/java/d/D.java | 7 +++ .../pom.xml | 38 ++++++++++++ .../super-pom/pom.xml | 25 ++++++++ 13 files changed, 307 insertions(+), 2 deletions(-) create mode 100644 its/core-it-suite/src/test/java/org/apache/maven/it/MavenITgh12646ProjectLocalRepoCleanRaceTest.java create mode 100644 its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/.mvn/.gitkeep create mode 100644 its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-a/pom.xml create mode 100644 its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-a/src/main/java/a/A.java create mode 100644 its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-b/pom.xml create mode 100644 its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-b/src/main/java/b/B.java create mode 100644 its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-c/pom.xml create mode 100644 its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-c/src/main/java/c/C.java create mode 100644 its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-d/pom.xml create mode 100644 its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-d/src/main/java/d/D.java create mode 100644 its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/pom.xml create mode 100644 its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/super-pom/pom.xml diff --git a/impl/maven-core/src/main/java/org/apache/maven/ReactorReader.java b/impl/maven-core/src/main/java/org/apache/maven/ReactorReader.java index db4882e38696..bd6fa348d942 100644 --- a/impl/maven-core/src/main/java/org/apache/maven/ReactorReader.java +++ b/impl/maven-core/src/main/java/org/apache/maven/ReactorReader.java @@ -40,6 +40,7 @@ import java.util.Map; import java.util.Objects; import java.util.concurrent.ConcurrentHashMap; +import java.util.concurrent.locks.ReentrantReadWriteLock; import java.util.stream.Collectors; import java.util.stream.Stream; @@ -82,6 +83,11 @@ class ReactorReader implements MavenWorkspaceReader { private Path projectLocalRepository; // projectId -> Deque private final Map> lifecycles = new ConcurrentHashMap<>(); + // Coordinates access to project-local-repo between clean and install operations. + // When the project that owns the project-local-repo directory is being cleaned + // (maven-clean-plugin deletes its entire target/ directory), the write lock prevents + // concurrent installs from writing into the directory being deleted. + private final ReentrantReadWriteLock projectLocalRepoLock = new ReentrantReadWriteLock(); @Inject ReactorReader(MavenSession session) { @@ -352,6 +358,11 @@ private File findInProjectLocalRepository(Artifact artifact) { * The mojo started event is also captured to determine the lifecycle * phases the project has been through. * + *

When the project that owns the project-local-repo directory enters its clean phase, + * we acquire a write lock to prevent concurrent installs from writing into the directory + * while maven-clean-plugin is deleting it. The lock is released when the clean mojo + * succeeds or fails.

+ * * @param event the execution event */ private void processEvent(ExecutionEvent event) { @@ -360,6 +371,9 @@ private void processEvent(ExecutionEvent event) { case MojoStarted: String phase = event.getMojoExecution().getLifecyclePhase(); if (phase != null) { + if ("clean".equals(phase) && isProjectLocalRepoOwner(project)) { + projectLocalRepoLock.writeLock().lock(); + } Deque phases = getLifecycles(project); if (!Objects.equals(phase, phases.peekLast())) { phases.addLast(phase); @@ -371,10 +385,24 @@ private void processEvent(ExecutionEvent event) { } } break; + case MojoSucceeded: + case MojoFailed: + String endedPhase = event.getMojoExecution().getLifecyclePhase(); + if ("clean".equals(endedPhase) && isProjectLocalRepoOwner(project)) { + if (projectLocalRepoLock.isWriteLockedByCurrentThread()) { + projectLocalRepoLock.writeLock().unlock(); + } + } + break; case ProjectSucceeded: case ForkedProjectSucceeded: - synchronized (project) { - installIntoProjectLocalRepository(project); + projectLocalRepoLock.readLock().lock(); + try { + synchronized (project) { + installIntoProjectLocalRepository(project); + } + } finally { + projectLocalRepoLock.readLock().unlock(); } break; default: @@ -386,6 +414,17 @@ private Deque getLifecycles(MavenProject project) { return lifecycles.computeIfAbsent(project.getId(), k -> new ArrayDeque<>()); } + /** + * Checks whether the given project's build directory contains the project-local-repo. + * When this project's clean phase runs, maven-clean-plugin will delete the build directory, + * which would race with concurrent installs writing to project-local-repo. + */ + private boolean isProjectLocalRepoOwner(MavenProject project) { + Path projectLocalRepo = getProjectLocalRepo(); + Path buildDir = Paths.get(project.getBuild().getDirectory()); + return projectLocalRepo.startsWith(buildDir); + } + /** * Copy packaged and attached artifacts from this project to the * project local repository. diff --git a/its/core-it-suite/src/test/java/org/apache/maven/it/MavenITgh12646ProjectLocalRepoCleanRaceTest.java b/its/core-it-suite/src/test/java/org/apache/maven/it/MavenITgh12646ProjectLocalRepoCleanRaceTest.java new file mode 100644 index 000000000000..bc06787f36e0 --- /dev/null +++ b/its/core-it-suite/src/test/java/org/apache/maven/it/MavenITgh12646ProjectLocalRepoCleanRaceTest.java @@ -0,0 +1,59 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, + * software distributed under the License is distributed on an + * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY + * KIND, either express or implied. See the License for the + * specific language governing permissions and limitations + * under the License. + */ +package org.apache.maven.it; + +import java.nio.file.Path; + +import org.junit.jupiter.api.Test; + +/** + * This is a test set for GH-12646. + * + * Verifies that parallel builds with {@code clean install} do not fail with a race condition + * when the root pom has a parent (super-pom) and other modules write to + * {@code target/project-local-repo} while the root project's clean phase is running. + * + * @since 4.0.0-rc-6 + */ +class MavenITgh12646ProjectLocalRepoCleanRaceTest extends AbstractMavenIntegrationTestCase { + + /** + * Verify that a parallel {@code clean install} succeeds when the root pom has a parent + * that is also part of the reactor. In this scenario: + *
    + *
  1. super-pom builds first (no dependencies)
    2. + *
  2. root pom and module-a..d start in parallel (all depend on super-pom)
    3. + *
  3. root pom's clean phase runs maven-clean-plugin which deletes target/
    4. + *
  4. modules complete and install artifacts into target/project-local-repo
    5. + *
+ * Without the fix, step 3 and 4 race, causing maven-clean-plugin to fail because + * target/project-local-repo is being written to while it tries to delete target/. + */ + @Test + void testParallelCleanInstallWithParentPom() throws Exception { + Path testDir = extractResources("gh-12646-project-local-repo-clean-race"); + + Verifier verifier = newVerifier(testDir); + verifier.addCliArgument("-T"); + verifier.addCliArgument("4"); + verifier.addCliArguments("clean", "install"); + verifier.execute(); + verifier.verifyErrorFreeLog(); + } +} diff --git a/its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/.mvn/.gitkeep b/its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/.mvn/.gitkeep new file mode 100644 index 000000000000..e69de29bb2d1 diff --git a/its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-a/pom.xml b/its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-a/pom.xml new file mode 100644 index 000000000000..0bd336766545 --- /dev/null +++ b/its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-a/pom.xml @@ -0,0 +1,29 @@ + + + + + org.apache.maven.its.gh12646 + super-pom + 1.0-SNAPSHOT + ../super-pom + + + module-a + diff --git a/its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-a/src/main/java/a/A.java b/its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-a/src/main/java/a/A.java new file mode 100644 index 000000000000..4f3732128374 --- /dev/null +++ b/its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-a/src/main/java/a/A.java @@ -0,0 +1,7 @@ +package a; + +public class A { + public String greet() { + return "Hello from A"; + } +} diff --git a/its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-b/pom.xml b/its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-b/pom.xml new file mode 100644 index 000000000000..cc2481ca8048 --- /dev/null +++ b/its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-b/pom.xml @@ -0,0 +1,29 @@ + + + + + org.apache.maven.its.gh12646 + super-pom + 1.0-SNAPSHOT + ../super-pom + + + module-b + diff --git a/its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-b/src/main/java/b/B.java b/its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-b/src/main/java/b/B.java new file mode 100644 index 000000000000..0dda156c7e65 --- /dev/null +++ b/its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-b/src/main/java/b/B.java @@ -0,0 +1,7 @@ +package b; + +public class B { + public String greet() { + return "Hello from B"; + } +} diff --git a/its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-c/pom.xml b/its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-c/pom.xml new file mode 100644 index 000000000000..118156c2f73a --- /dev/null +++ b/its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-c/pom.xml @@ -0,0 +1,29 @@ + + + + + org.apache.maven.its.gh12646 + super-pom + 1.0-SNAPSHOT + ../super-pom + + + module-c + diff --git a/its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-c/src/main/java/c/C.java b/its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-c/src/main/java/c/C.java new file mode 100644 index 000000000000..55e1d95b650c --- /dev/null +++ b/its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-c/src/main/java/c/C.java @@ -0,0 +1,7 @@ +package c; + +public class C { + public String greet() { + return "Hello from C"; + } +} diff --git a/its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-d/pom.xml b/its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-d/pom.xml new file mode 100644 index 000000000000..88e8aa163899 --- /dev/null +++ b/its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-d/pom.xml @@ -0,0 +1,29 @@ + + + + + org.apache.maven.its.gh12646 + super-pom + 1.0-SNAPSHOT + ../super-pom + + + module-d + diff --git a/its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-d/src/main/java/d/D.java b/its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-d/src/main/java/d/D.java new file mode 100644 index 000000000000..fba6e63f6878 --- /dev/null +++ b/its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-d/src/main/java/d/D.java @@ -0,0 +1,7 @@ +package d; + +public class D { + public String greet() { + return "Hello from D"; + } +} diff --git a/its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/pom.xml b/its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/pom.xml new file mode 100644 index 000000000000..9c80f90a35f3 --- /dev/null +++ b/its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/pom.xml @@ -0,0 +1,38 @@ + + + + + org.apache.maven.its.gh12646 + super-pom + 1.0-SNAPSHOT + super-pom + + + root + pom + + + super-pom + module-a + module-b + module-c + module-d + + diff --git a/its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/super-pom/pom.xml b/its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/super-pom/pom.xml new file mode 100644 index 000000000000..9df54d716ac8 --- /dev/null +++ b/its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/super-pom/pom.xml @@ -0,0 +1,25 @@ + + + + org.apache.maven.its.gh12646 + super-pom + 1.0-SNAPSHOT + pom + From e1110f7d56d44376c26cecaaf6114dbd5e580c77 Mon Sep 17 00:00:00 2001 From: Guillaume Nodet Date: Fri, 31 Jul 2026 23:26:30 +0200 Subject: [PATCH 2/2] Fix #12646: move project-local-repo from target/ to .mvn/ to eliminate clean race MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 --- .../java/org/apache/maven/ReactorReader.java | 70 ++++--------------- 1 file changed, 15 insertions(+), 55 deletions(-) diff --git a/impl/maven-core/src/main/java/org/apache/maven/ReactorReader.java b/impl/maven-core/src/main/java/org/apache/maven/ReactorReader.java index bd6fa348d942..8217c743e48a 100644 --- a/impl/maven-core/src/main/java/org/apache/maven/ReactorReader.java +++ b/impl/maven-core/src/main/java/org/apache/maven/ReactorReader.java @@ -40,7 +40,6 @@ import java.util.Map; import java.util.Objects; import java.util.concurrent.ConcurrentHashMap; -import java.util.concurrent.locks.ReentrantReadWriteLock; import java.util.stream.Collectors; import java.util.stream.Stream; @@ -83,11 +82,6 @@ class ReactorReader implements MavenWorkspaceReader { private Path projectLocalRepository; // projectId -> Deque private final Map> lifecycles = new ConcurrentHashMap<>(); - // Coordinates access to project-local-repo between clean and install operations. - // When the project that owns the project-local-repo directory is being cleaned - // (maven-clean-plugin deletes its entire target/ directory), the write lock prevents - // concurrent installs from writing into the directory being deleted. - private final ReentrantReadWriteLock projectLocalRepoLock = new ReentrantReadWriteLock(); @Inject ReactorReader(MavenSession session) { @@ -358,10 +352,11 @@ private File findInProjectLocalRepository(Artifact artifact) { * The mojo started event is also captured to determine the lifecycle * phases the project has been through. * - *

When the project that owns the project-local-repo directory enters its clean phase, - * we acquire a write lock to prevent concurrent installs from writing into the directory - * while maven-clean-plugin is deleting it. The lock is released when the clean mojo - * succeeds or fails.

+ *

When a project enters its clean phase, its artifacts are cleaned from the + * project-local-repo (per-GAV scope). Since the project-local-repo is located + * under {@code .mvn/} (not under {@code target/}), it is not affected by + * maven-clean-plugin's deletion of {@code target/}, eliminating the race + * condition between clean and install operations in parallel builds.

* * @param event the execution event */ @@ -371,38 +366,19 @@ private void processEvent(ExecutionEvent event) { case MojoStarted: String phase = event.getMojoExecution().getLifecyclePhase(); if (phase != null) { - if ("clean".equals(phase) && isProjectLocalRepoOwner(project)) { - projectLocalRepoLock.writeLock().lock(); - } Deque phases = getLifecycles(project); if (!Objects.equals(phase, phases.peekLast())) { phases.addLast(phase); if ("clean".equals(phase)) { - synchronized (project) { - cleanProjectLocalRepository(project); - } + cleanProjectLocalRepository(project); } } } break; - case MojoSucceeded: - case MojoFailed: - String endedPhase = event.getMojoExecution().getLifecyclePhase(); - if ("clean".equals(endedPhase) && isProjectLocalRepoOwner(project)) { - if (projectLocalRepoLock.isWriteLockedByCurrentThread()) { - projectLocalRepoLock.writeLock().unlock(); - } - } - break; case ProjectSucceeded: case ForkedProjectSucceeded: - projectLocalRepoLock.readLock().lock(); - try { - synchronized (project) { - installIntoProjectLocalRepository(project); - } - } finally { - projectLocalRepoLock.readLock().unlock(); + synchronized (project) { + installIntoProjectLocalRepository(project); } break; default: @@ -414,17 +390,6 @@ private Deque getLifecycles(MavenProject project) { return lifecycles.computeIfAbsent(project.getId(), k -> new ArrayDeque<>()); } - /** - * Checks whether the given project's build directory contains the project-local-repo. - * When this project's clean phase runs, maven-clean-plugin will delete the build directory, - * which would race with concurrent installs writing to project-local-repo. - */ - private boolean isProjectLocalRepoOwner(MavenProject project) { - Path projectLocalRepo = getProjectLocalRepo(); - Path buildDir = Paths.get(project.getBuild().getDirectory()); - return projectLocalRepo.startsWith(buildDir); - } - /** * Copy packaged and attached artifacts from this project to the * project local repository. @@ -441,6 +406,12 @@ private void installIntoProjectLocalRepository(MavenProject project) { } } + /** + * Cleans the project-local-repo artifacts for the given project's GAV coordinates. + * Since the project-local-repo is under {@code .mvn/} and not {@code target/}, + * it is not affected by maven-clean-plugin's deletion of {@code target/}, + * so there is no race between clean and install operations in parallel builds. + */ private void cleanProjectLocalRepository(MavenProject project) { try { Path artifactPath = getProjectLocalRepo() @@ -544,18 +515,7 @@ private Path getArtifactPath( private Path getProjectLocalRepo() { if (projectLocalRepository == null) { Path root = session.getRequest().getRootDirectory(); - List projects = session.getProjects(); - if (projects != null) { - projectLocalRepository = projects.stream() - .filter(project -> Objects.equals(root.toFile(), project.getBasedir())) - .findFirst() - .map(project -> project.getBuild().getDirectory()) - .map(Paths::get) - .orElseGet(() -> root.resolve("target")) - .resolve(PROJECT_LOCAL_REPO); - } else { - return root.resolve("target").resolve(PROJECT_LOCAL_REPO); - } + projectLocalRepository = root.resolve(".mvn").resolve(PROJECT_LOCAL_REPO); } return projectLocalRepository; }