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https://issues.apache.org/jira/browse/MNG-6412?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16615153#comment-16615153
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Sylwester Lachiewicz commented on MNG-6412:
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Thanks for the sample projects. They helped a lot.
I think we've fixed the caching problem in MNG-6311, these sample designs build
in a few seconds. I have not noticed any problems with memory so far, but if
you can check build based on the 3.6.0-SNAPSHOT version from master I will be
grateful.
> Exceeding project discovery time when using CI friendly versions
> ----------------------------------------------------------------
>
> Key: MNG-6412
> URL: https://issues.apache.org/jira/browse/MNG-6412
> Project: Maven
> Issue Type: Bug
> Affects Versions: 3.5.3
> Reporter: Christoph Amshoff
> Assignee: Sylwester Lachiewicz
> Priority: Critical
> Fix For: 3.6.0
>
> Attachments: ci-version-validate.log, fix-version-validate.log,
> test-ci-project-scanning.zip
>
>
> We are switching a larger project to CI friendly versions
> ([https://maven.apache.org/maven-ci-friendly.html]), using properties
> _${revision}_ (fix) and _${changelist}_ (maps to the CI build number) to
> create the actual version. However, doing so, the project discovery time
> (right after Maven says “Scanning for projects...”) increases dramatically
> from few seconds to more than 3 minutes, and we had to double the maximum
> heap in order to avoid “GC overhead limit exceeded” exception.
> The project root POM looks like this:
> {noformat}
> <groupId>test</groupId>
> <artifactId>parent</artifactId>
> <version>${revision}-${changelist}</version>
> <packaging>pom</packaging>
> ...
> <properties>
> <revision>1.0.0</revision>
> <changelist>UNDEFINED</changelist>
> </properties> {noformat}
> and is built by passing “-Dchangelist=123” to the Maven process for CI build
> 123, for instance.
> In debug output, we can see that for each POM of the reactor there are
> messages like these, repeatedly for every single parent POM up the complete
> hierarchy:
> {noformat}
> [DEBUG] Extension realms for project test:grandchild1-1:jar:1.0.0-123: (none)
> [DEBUG] Looking up lifecycle mappings for packaging jar from
> ClassRealm[plexus.core, parent: null]
> [DEBUG] Extension realms for project test:child1:pom:1.0.0-123: (none)
> [DEBUG] Looking up lifecycle mappings for packaging pom from
> ClassRealm[plexus.core, parent: null]
> [DEBUG] Extension realms for project test:parent:pom:1.0.0-123: (none)
> [DEBUG] Looking up lifecycle mappings for packaging pom from
> ClassRealm[plexus.core, parent: null]
> {noformat}
> When using fix version string (release or SNAPSHOT), these messages are only
> present for the reactor POMs, but not their parents, grand-parents, etc. up
> to the root POM.
> Looking up the lifecycle mapping for the same parent POMs over and over again
> seems wrong to me, and is probably the cause of high memory consumption.
> Altogether, there are more than 2,800 messages "Looking up lifecycle
> mappings..." in the logs for about 350 subprojects built in the reactor!
> See attached test projects and logs for fix version vs. CI friendly versions.
> The test project structure is like this:
> {noformat}
> parent
> child1
> grandchild1-1
> grandchild1-2
> child2
> grandchild2-1
> grandchild2-2{noformat}
> If you compare both log files, you'll see the difference in project resolving.
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