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  1. Maven
  2. MNG-5687

Parallel Builds can build in wrong order



    • Type: Bug
    • Status: Closed
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: 3.2.3
    • Fix Version/s: 3.2.5
    • Component/s: General
    • Labels:
    • Environment:
      Best visibility on jdk8


      Fixed JDK8 IT failure for MavenITmng3004ReactorFailureBehaviorMultithreadedTest#testitFailFastSingleThread

      It turns out the execution order of the modules in the build can be incorrect, in some cases severely incorrect.
      For parallel builds this can have all sorts of interesting side effects such as classpath
      appearing to be intermittently incorrect, missing jars/resources and similar.

      The -am options and -amd options may simply fail with the incorrect build order
      because expected dependencies have not been built and actual dependencies may not have been built.

      The underlying problem was that ProjectDependencyGraph#getDownstreamProjects and getUpstreamProjects
      did not actually obey the reactor build order as defined by ProjectDependencyGraph#getSortedProjects,
      even though the javadoc claims they should.

      This has only worked by accident on earlier JDK's and might not have worked at all (basically
      depends on Set iteration order being equal to insertion order). JDK8 has slightly different
      iteration order, which caused the IT failure.

      This problem may be the root cause of MNG-4996 and any other issue where the modules build
      in incorrect order.

      The bug affects:

      parallel builds
      command line am (-also-make) option
      command line -amd (also-make-dependents) option

      On all java versions, although visibility might be somewhat different on different jdks.

      Added simple unit test that catches the problem.


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              • Assignee:
                krosenvold Kristian Rosenvold
                krosenvold Kristian Rosenvold
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