Christoph Amshoff created MNG-6412:
--------------------------------------

             Summary: 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
         Attachments: fix-version-validate.log, test-ci-project-scanning.zip

We are switching a larger project (> 350 subprojects) 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.



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