[jira] [Commented] (MNG-4738) DefaultArtifactResolver forks non-daemon threads

["Delany (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MNG-4738?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17251638#comment-17251638 ] 

Delany commented on MNG-4738:
-----------------------------

How can I see the default/effective value of maven.artifact.threads?

Changing the value in settings or from command line seems to have no effect on the rate of resolution.

 

> DefaultArtifactResolver forks non-daemon threads
> ------------------------------------------------
>
>                 Key: MNG-4738
>                 URL: https://issues.apache.org/jira/browse/MNG-4738
>             Project: Maven
>          Issue Type: Bug
>          Components: Embedding
>    Affects Versions: 3.0-beta-1
>         Environment: Ubuntu Lucid, JDK 6u21
>            Reporter: Jesse N. Glick
>            Assignee: Benjamin Bentmann
>            Priority: Minor
>             Fix For: 3.0-beta-2
>
>         Attachments: MNG-4738-hanzelm.diff, MNG-4738-hanzelm2-reformat.diff, MNG-4738-hanzelm2.diff, MNG-4738.diff
>
>
> I am working on embedding Maven 3 (beta 1). I ran into a problem with Maven execution hanging at the end.
> When we run a "process" in-VM, we try to emulate a forked Java as much as is reasonable. A new thread group is created, whatever work needs to be done is done from a new thread in that group, and then we wait for the "process" to end by checking that all non-daemon threads in the group have exited.
> In the case of Maven execution, typically DefaultArtifactResolver is called at some point. By default, this creates a ThreadPoolExecutor with 5 non-daemon threads in it (which are created inside the thread group of the caller). Although all tasks are certainly completed by the end of the Maven run, these 5 threads remain alive, and so the thread group cannot be considered dead.
> It seems to me that DefaultArtifactResolver is at fault here. It should not be spawning non-daemon threads. Although it shuts down the executor upon being finalized, there is no guarantee of this happening in a timely manner.
> Since the tasks being run in the threads are only active within the dynamic scope of calls to resolve, it should be safe to mark the executor threads as daemon. I would be happy to supply a patch incl. test case if you agree with the premise.
> The workaround is to set maven.artifact.threads=1 before starting Maven execution, so that no threads need be spawned at all.



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