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https://issues.apache.org/jira/browse/MNG-7509?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17573784#comment-17573784
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ASF GitHub Bot commented on MNG-7509:
-------------------------------------
Yougoss commented on PR #768:
URL: https://github.com/apache/maven/pull/768#issuecomment-1201264110
> mentioned
Currently, I just made this potential enhancement for branch 3.8.x and
3.9.x.
For maven 4, I have checked the code roughly, the classes in change list
have been modified (seems that refine some iterate from for to stream api).
There should be the same issue in maven 4 as well, but the code change may be a
little different since the code base are different.
So I just want to confirm current solution is OK first. Then I can apply
similar change for maven 4.
> 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
> Fix For: 3.9.0-candidate, 4.0.x-candidate
>
> 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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