[jira] [Updated] (MESOS-2198) Document that TaskIDs should not be reused

["Neil Conway (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/MESOS-2198?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Neil Conway updated MESOS-2198:
-------------------------------
    Shepherd: Jie Yu

> Document that TaskIDs should not be reused
> ------------------------------------------
>
>                 Key: MESOS-2198
>                 URL: https://issues.apache.org/jira/browse/MESOS-2198
>             Project: Mesos
>          Issue Type: Bug
>          Components: documentation, framework
>            Reporter: Robert Lacroix
>            Assignee: Neil Conway
>              Labels: documentation
>
> Let's update the documentation for TaskID to indicate that reuse is not recommended, as per the discussion below.
> -------------
> Old Summary: Scheduler#statusUpdate should not be called multiple times for the same status update
> Currently Scheduler#statusUpdate can be called multiple times for the same status update, for example when the slave retransmits a status update because it's not acknowledged in time. Especially for terminal status updates this can lead to unexpected scheduler behavior when task id's are being reused.
> Consider this scenario:
> * Scheduler schedules task
> * Task fails, slave sends TASK_FAILED
> * Scheduler is busy and libmesos doesn't acknowledge update in time
> * Slave retransmits TASK_FAILED
> * Scheduler eventually receives first TASK_FAILED and reschedules task
> * Second TASK_FAILED triggers statusUpdate again and the scheduler can't determine if the TASK_FAILED belongs to the first or second run of the task.
> It would be a lot better if libmesos would dedupe status updates and only call Scheduler#statusUpdate once per status update it received. Retries with the same UUID shouldn't cause Scheduler#statusUpdate to be executed again.



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