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https://issues.apache.org/jira/browse/MNG-6311?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16700807#comment-16700807
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Mickael Istria commented on MNG-6311:
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I think this change should be reverted as it's not backward compatible. Unless
I'm mistaken, this caching makes that 2 distinct calls to
ProjectBuilder.build(pomFile) would always return the same result even if the
content of pomFile did change. It's almost certain that m2e will face a bug and
other clients of ProjectBuilder may face bugs too.
This case of changing pom content being modified and ProjectBuilder.build(...)
returning the same result should be covered by a unit test (I may try write
one).
Caching is a good idea, but it also need to take into account the modification
date to not cause bug in dynamic world.
> Maven intolerably slow when import scope used heavily in large project
> ----------------------------------------------------------------------
>
> Key: MNG-6311
> URL: https://issues.apache.org/jira/browse/MNG-6311
> Project: Maven
> Issue Type: Bug
> Components: core, Performance
> Affects Versions: 3.5.0, 3.5.2
> Reporter: David Churcher
> Assignee: Sylwester Lachiewicz
> Priority: Major
> Labels: performance
> Fix For: 3.6.0
>
> Attachments: Call-tree-–-All-threads-together.html,
> anon-hierarchy-maven-output.zip, modelcachefix.diff
>
>
> I have a build performance problem that is identical to MNG-5312, and has
> appeared since MNG-6030 in Maven v3.5.0 reversed the patch for MNG-5312,
> removing the ModelCache from some of the overloads for
> DefaultProjectBuilder.build.
> As in MNG-5312 the problem is in a large proprietary project. It uses up to 8
> levels of parent POMs, many of which use the import scope and have large
> dependency-management sections, and has hundreds of dependencies that also
> use the same parent POM hierarchy. Adding some logging shows that Maven does
> over 800,000 uncached reads of parent POM files, which takes about half an
> hour. With model caching this goes down to a few seconds.
> I've attached a patch that fixes this by using a class-level ModelCache in
> DefaultProjectBuilder. This does not suffer from the memory usage problems
> reported in MNG-6030.
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