[Bug]: large numbers of dependencies exhaust heap memory during dependency resolution

[estekhin]

Hi!

I am trying to switch from xolstice/protobuf-maven-plugin to ascopes/protobuf-maven-plugin, but getting some unexpected results.

Our setup:

• a separate "proto" project with a lot of proto files which generates a bunch of artifacts with generated class files and embedded proto files
• the "main" multi-module project that depends on proto-project artifacts as necessary, with a couple of modules that have their own proto files

I have configured <embedSourcesInClassOutputs>true</embedSourcesInClassOutputs> because it matches the default xolstice behaviour.

Most modules are OK after switching to ascopes.
Some modules that both have their own proto files and depend on a lot of proto-project artifacts cause OOME.

-X log looks like this:

[INFO] --- protobuf:2.12.1:generate (generate) @ unlucky-module ---
...
[DEBUG] Configuring mojo execution 'io.github.ascopes:protobuf-maven-plugin:2.12.1:generate:generate' with basic configurator -->
...
[DEBUG] Resolving artifact: MavenDependency{groupId=com.google.protobuf, artifactId=protoc, version=3.25.5, type=exe, classifier=linux-x86_64, dependencyResolutionDepth=null, exclusions=[]}
[DEBUG] Resolved extension exe to Aether artifact type (classifier: "", type: "exe", id: "exe", "{language=none, constitutesBuildPath=false, type=exe, includesDependencies=false}")
[INFO] Resolving artifact com.google.protobuf:protoc:exe:linux-x86_64:3.25.5 from repositories
[DEBUG] Discovering all compilable protobuf source files
[DEBUG] Attempting to resolve the following dependencies in this pass: []
...
// a long list of unlucky-module dependencies goes here
[DEBUG] Resolving project dependency: Dependency {groupId=..., artifactId=..., version=..., type=...}
...
[DEBUG] Attempting to resolve the following dependencies in this pass: [non-empty list, contains unlucky-module dependencies]

at this point the log "stops" for some time, and then fails with

[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  03:31 min (Wall Clock)
[INFO] Finished at: 2025-03-17T16:10:36+03:00
[INFO] ------------------------------------------------------------------------
[ERROR] Java heap space -> [Help 1]
java.lang.OutOfMemoryError: Java heap space
    at java.util.ArrayList.grow (ArrayList.java:240)
    at java.util.ArrayList.grow (ArrayList.java:245)
    at java.util.ArrayList.add (ArrayList.java:484)
    at java.util.ArrayList.add (ArrayList.java:497)
    at org.eclipse.aether.resolution.VersionRangeResult.addVersion (VersionRangeResult.java:116)
    at org.eclipse.aether.internal.impl.collect.DataPool$Constraint.toResult (DataPool.java:352)
    at org.eclipse.aether.internal.impl.collect.DataPool.getConstraint (DataPool.java:227)
    at org.eclipse.aether.internal.impl.collect.DependencyCollectorDelegate.cachedResolveRangeResult (DependencyCollectorDelegate.java:404)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:202)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:156)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.process (DfDependencyCollector.java:138)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.doRecurse (DfDependencyCollector.java:343)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:277)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:156)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.process (DfDependencyCollector.java:138)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.doRecurse (DfDependencyCollector.java:343)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:277)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:156)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.process (DfDependencyCollector.java:138)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.doRecurse (DfDependencyCollector.java:343)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:277)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:156)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.process (DfDependencyCollector.java:138)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.doRecurse (DfDependencyCollector.java:343)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:277)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:156)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.process (DfDependencyCollector.java:138)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.doRecurse (DfDependencyCollector.java:343)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:277)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:156)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.process (DfDependencyCollector.java:138)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.doRecurse (DfDependencyCollector.java:343)

This is the only stacktrace it reports, and there are no plugin-related packages or classes in the stacktrace.

I have tried to use <dependencyResolutionDepth>DIRECT</dependencyResolutionDepth>, but it results in the same OOME.

I have tried to use <ignoreProjectDependencies>true</ignoreProjectDependencies> - it kind of solves the problem, but it requires to specify <importDependencies> with duplicates of some project dependencies (and it seems it doesn't use dependency management and requires to specify the version explicitly, but that is a separate issue).

[ascopes]

Hey, thanks for raising this. Apologies for the inconvenience!

Are you able to provide a minimal working reproduction for this issue or details on how many dependencies you have? It may be very difficult to reproduce this otherwise if it is dependant on a very complex configuration. If not, something like a flight recording or histogram of the JVM memory usage may be able to help me work out what is causing this.

Please can you also provide details about the JDK, and Maven version in use?

[ascopes]

Also, regarding dependency management, that is on track for 2.13.0, worked on setting that up yesterday. Just ironing out a few rough edges at the moment.

[ascopes]

I might have worked out your issue. Please can you build the branch at GH-598 locally and try it out to see if it resolves your issue?

./mvnw clean install -Dinvoker.skip -Dmaven.test.skip

[estekhin]

Please can you also provide details about the JDK, and Maven version in use?

Maven 3.9.9
JDK 23.0.2

[estekhin]

Are you able to provide a minimal working reproduction for this issue or details on how many dependencies you have? It may be very difficult to reproduce this otherwise if it is dependant on a very complex configuration. If not, something like a flight recording or histogram of the JVM memory usage may be able to help me work out what is causing this.

I definitely can reproduce it "on my machine", but can't think of how to create an isolated example because i don't understand the root cause yet.

I have tried to run the maven with -XX:MaxJavaStackTraceDepth=100000 but it seems that OOME is tricky in this regard because i didn't get any changes in the OOME stack trace content.

I will check if i will be able to do JFR or heap or thread dump later.

[ascopes]

Thanks for the info, would be worth trying the branch at GH-598 first as I believe this is likely related to your issue. If that fixes it, I won't need any further diagnostics hopefully.

I'm hoping the Aether references in the stacktrace are a red herring, since it is the same mechanism that Maven is using already to resolve dependencies, so I'd expect it to be failing regardless of whether the plugin is used or not in that case.

[estekhin]

I might have worked out your issue. Please can you build the branch at GH-598 locally and try it out to see if it resolves your issue?

./mvnw clean install -Dinvoker.skip -Dmaven.test.skip

[INFO] --- protobuf:2.13.0-SNAPSHOT:generate (generate) @ unlucky-module ---
[DEBUG] Loading mojo io.github.ascopes:protobuf-maven-plugin:2.13.0-SNAPSHOT:generate from plugin realm ClassRealm[plugin>io.github.ascopes:protobuf-maven-plugin:2.13.0-SNAPSHOT, parent: jdk.internal.loader.ClassLoaders$AppClassLoader@2f6cfdf6]
...
[DEBUG] Effective concurrency is 80, default concurrency is 80. Override this by passing -Dprotobuf.executor.maxThreads=value
[DEBUG] Configuring mojo execution 'io.github.ascopes:protobuf-maven-plugin:2.13.0-SNAPSHOT:generate:generate' with basic configurator -->
[DEBUG]   (f) cppEnabled = false
[DEBUG]   (f) csharpEnabled = false
[DEBUG]   (f) dependencyResolutionDepth = TRANSITIVE
[DEBUG]   (f) embedSourcesInClassOutputs = false
[DEBUG]   (f) excludes = []
[DEBUG]   (f) failOnInvalidDependencies = false
[DEBUG]   (f) failOnMissingSources = true
[DEBUG]   (f) failOnMissingTargets = true
[DEBUG]   (f) fatalWarnings = false
[DEBUG]   (f) ignoreProjectDependencies = false
[DEBUG]   (f) includes = []
[DEBUG]   (f) incrementalCompilation = true
[DEBUG]   (f) javaEnabled = true
[DEBUG]   (f) kotlinEnabled = false
[DEBUG]   (f) liteOnly = false
[DEBUG]   (f) objcEnabled = false
[DEBUG]   (f) outputDescriptorAttached = false
[DEBUG]   (f) outputDescriptorIncludeImports = false
[DEBUG]   (f) outputDescriptorIncludeSourceInfo = false
[DEBUG]   (f) outputDescriptorRetainOptions = false
[DEBUG]   (f) phpEnabled = false
[DEBUG]   (f) protocVersion = 3.25.5
[DEBUG]   (f) pythonEnabled = false
[DEBUG]   (f) pythonStubsEnabled = false
[DEBUG]   (f) registerAsCompilationRoot = true
[DEBUG]   (f) rubyEnabled = false
[DEBUG]   (f) rustEnabled = false
[DEBUG]   (f) skip = false
[DEBUG] -- end configuration --
...
[DEBUG] Resolving artifact: MavenDependency{groupId=com.google.protobuf, artifactId=protoc, version=3.25.5, type=exe, classifier=linux-x86_64, dependencyResolutionDepth=null, exclusions=[]}
[DEBUG] Resolved extension exe to Aether artifact type (classifier: "", type: "exe", id: "exe", "{language=none, constitutesBuildPath=false, type=exe, includesDependencies=false}")
[INFO] Attempting to resolve artifact com.google.protobuf:protoc:exe:linux-x86_64:3.25.5
[DEBUG] Discovering all compilable protobuf source files
[INFO] Resolving 0 dependencies
[DEBUG] Attempting to resolve the following dependencies: []
...
a bunch of
[DEBUG] Resolving project dependency: Dependency {groupId=..., artifactId=..., version=..., type=...}
...
[INFO] Resolving 67 dependencies
[DEBUG] Attempting to resolve the following dependencies: [non-empty list of dependencies]

OOME with a slightly different stacktrace

ERROR] Java heap space -> [Help 1]
java.lang.OutOfMemoryError: Java heap space
    at java.util.ArrayList.iterator (ArrayList.java:1030)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:210)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:156)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.process (DfDependencyCollector.java:138)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.doRecurse (DfDependencyCollector.java:343)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:277)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:156)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.process (DfDependencyCollector.java:138)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.doRecurse (DfDependencyCollector.java:343)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:277)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:156)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.process (DfDependencyCollector.java:138)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.doRecurse (DfDependencyCollector.java:343)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:277)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:156)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.process (DfDependencyCollector.java:138)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.doRecurse (DfDependencyCollector.java:343)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:277)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:156)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.process (DfDependencyCollector.java:138)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.doRecurse (DfDependencyCollector.java:343)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:277)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:156)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.process (DfDependencyCollector.java:138)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.doRecurse (DfDependencyCollector.java:343)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:277)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:156)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.process (DfDependencyCollector.java:138)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.doRecurse (DfDependencyCollector.java:343)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:277)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:156)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.process (DfDependencyCollector.java:138)
[ERROR] java.lang.OutOfMemoryError: Java heap space
java.util.concurrent.ExecutionException: java.lang.OutOfMemoryError: Java heap space
    at java.util.concurrent.FutureTask.report (FutureTask.java:122)
    at java.util.concurrent.FutureTask.get (FutureTask.java:191)
    at org.apache.maven.lifecycle.internal.builder.multithreaded.MultiThreadedBuilder.multiThreadedProjectTaskSegmentBuild (MultiThreadedBuilder.java:140)
    at org.apache.maven.lifecycle.internal.builder.multithreaded.MultiThreadedBuilder.build (MultiThreadedBuilder.java:101)
    at org.apache.maven.lifecycle.internal.LifecycleStarter.execute (LifecycleStarter.java:118)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:261)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:173)
    at org.apache.maven.DefaultMaven.execute (DefaultMaven.java:101)
    at org.apache.maven.cli.MavenCli.execute (MavenCli.java:906)
    at org.apache.maven.cli.MavenCli.doMain (MavenCli.java:283)
    at org.apache.maven.cli.MavenCli.main (MavenCli.java:206)
    at jdk.internal.reflect.DirectMethodHandleAccessor.invoke (DirectMethodHandleAccessor.java:103)
    at java.lang.reflect.Method.invoke (Method.java:580)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced (Launcher.java:255)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launch (Launcher.java:201)
    at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode (Launcher.java:361)
    at org.codehaus.plexus.classworlds.launcher.Launcher.main (Launcher.java:314)
Caused by: java.lang.OutOfMemoryError: Java heap space
    at java.util.ArrayList.iterator (ArrayList.java:1030)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:210)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:156)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.process (DfDependencyCollector.java:138)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.doRecurse (DfDependencyCollector.java:343)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:277)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:156)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.process (DfDependencyCollector.java:138)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.doRecurse (DfDependencyCollector.java:343)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:277)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:156)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.process (DfDependencyCollector.java:138)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.doRecurse (DfDependencyCollector.java:343)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:277)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:156)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.process (DfDependencyCollector.java:138)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.doRecurse (DfDependencyCollector.java:343)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:277)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:156)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.process (DfDependencyCollector.java:138)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.doRecurse (DfDependencyCollector.java:343)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:277)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:156)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.process (DfDependencyCollector.java:138)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.doRecurse (DfDependencyCollector.java:343)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:277)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:156)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.process (DfDependencyCollector.java:138)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.doRecurse (DfDependencyCollector.java:343)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:277)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.processDependency (DfDependencyCollector.java:156)
    at org.eclipse.aether.internal.impl.collect.df.DfDependencyCollector.process (DfDependencyCollector.java:138)

[estekhin]

I have also tried the following configuration

[INFO] --- protobuf:2.13.0-SNAPSHOT:generate (generate) @ unlicky-module
...
[DEBUG]   (f) dependencyResolutionDepth = DIRECT
[DEBUG]   (f) ignoreProjectDependencies = false

i was thinking that maybe dependencyResolutionDepth=DIRECT should limit the dependency resolution process to the dependencies explicitly specified in the pom (seems like there are 67 of them) without the need to go into any recursion, but it causes the same OOME.

[ascopes]

Do you happen to have a circular dependency anywhere that could be repeatedly trying to resolve itself somehow? That'd explain the deep stack trace.

67 dependencies shouldn't be enough to topple Aether over I would hope. That is fairly small in the grand scheme of things. The fact I can see it is saying it is recursing dependencies a lot makes me suspicious though. What does mvn dependency:tree suggest?

You could possibly attach a remote debugger to this to see what it is falling over on if need be. You'd need to run this repository in an IDE like IntelliJ and set up the remote debugger but I can talk you through that if needed.

https://github.com/apache/maven-resolver/blob/de21d1d0dce868c9dcc3782ef55a0afdb476e714/maven-resolver-impl/src/main/java/org/eclipse/aether/internal/impl/collect/df/DfDependencyCollector.java#L279 seems to be where it is recursing heavily.

If I can find a specific dependency causing the issue, I should be able to hopefully reproduce it.

[ascopes]

Also the dependency resolution depth setting applies to dependencies defined in the configuration of the plugin itself. It will still scan Maven POM dependencies by default. The configuration-based management of dependencies should work with dependency management now though on the copy you are running locally.