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https://issues.apache.org/jira/browse/MNG-7509?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17570282#comment-17570282
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ASF GitHub Bot commented on MNG-7509:
-------------------------------------
slawekjaranowski commented on code in PR #768:
URL: https://github.com/apache/maven/pull/768#discussion_r928105177
##########
maven-resolver-provider/src/test/java/org/apache/maven/repository/internal/ArtifactDescriptorReaderDelegateTest.java:
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@@ -0,0 +1,79 @@
+package org.apache.maven.repository.internal;
+
+import org.apache.maven.model.Dependency;
+import org.apache.maven.model.DependencyManagement;
+import org.apache.maven.model.Model;
+import org.eclipse.aether.artifact.DefaultArtifact;
+import org.eclipse.aether.resolution.ArtifactDescriptorRequest;
+import org.eclipse.aether.resolution.ArtifactDescriptorResult;
+
Review Comment:
please put imports before license.
> Huge memory cost when parent pom widely used in a big project for
> dependencyManagement
> --------------------------------------------------------------------------------------
>
> Key: MNG-7509
> URL: https://issues.apache.org/jira/browse/MNG-7509
> Project: Maven
> Issue Type: Improvement
> Components: Performance
> Reporter: Xiong Luyao
> Priority: Critical
> Attachments: image-2022-07-09-09-37-53-823.png,
> image-2022-07-09-09-38-26-354.png, image-2022-07-09-10-27-12-668.png,
> image-2022-07-09-10-27-56-437.png, image-2022-07-09-10-28-05-706.png,
> image-2022-07-09-10-28-22-864.png, image-2022-07-09-10-28-35-341.png,
> image-2022-07-09-10-28-40-612.png, image-2022-07-09-10-29-04-045.png,
> image-2022-07-09-10-29-15-822.png, image-2022-07-09-10-29-21-991.png,
> image-2022-07-09-10-29-46-216.png, image-2022-07-09-10-29-51-456.png
>
>
> When maven try to resolve dependency relationship, it will create many
> instances of dependency / artifact, even the dependency/artifact content is
> totally same, but just in different pom models. It cost huge memory if there
> is a parent pom with dependencyManagement which managed a lot of
> dependencies, and this parent pom are implemented by many project libraries.
> (libraries_count * managedDependency_count) dependency instances will be
> created. For example, if there are 3000 libraries, and all the library
> introduce same parent pom which managed 3000 dependencies version. There will
> be 3000*3000 =9,000,000 dependency instances will be created. But most of
> them are same, in fact, we only need one instance for each dependency in
> parent pom (3000 dependency instances).
>
> I'm from eBay, and here is a real case in enterprise level project. We have
> about 3000 business domain libraries, there are dependency relationship
> between them. We need to build all libraries in one release to keep all the
> libraries in same release are based on same code. So we used a parent pom as
> a central management to manage all the version for a release, and introduced
> by those libraries. As below picture, when the release start, it will
> calculate and start with the library which doesn't depend on others, then
> start the library which dependency libraries are already built. Keep this
> process until all libraries are built.
> With current maven resolve logic, it costs huge memory in above ways to built
> libraries. And even the libraries have been released, if the project which
> contains a lot of above libraries, it also cost huge memory when building
> project.
> So current now, we have to specify version in each library pom files instead
> of using parent pom. We think we can make some enhancement for this case.
>
> !image-2022-07-09-09-37-53-823.png|width=493,height=226!
>
> Here is a thread dump when building a real project which depends on about
> 1000 above libraries. The top 5 objects are all related to
> org.eclipse.aether.graph.Dependency.
> !image-2022-07-09-09-38-26-354.png|width=510,height=199!
>
>
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