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https://issues.apache.org/jira/browse/SPARK-20832?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Wenchen Fan reassigned SPARK-20832:
-----------------------------------
Assignee: Jiang Xingbo
> Standalone master should explicitly inform drivers of worker deaths and
> invalidate external shuffle service outputs
> -------------------------------------------------------------------------------------------------------------------
>
> Key: SPARK-20832
> URL: https://issues.apache.org/jira/browse/SPARK-20832
> Project: Spark
> Issue Type: Bug
> Components: Deploy, Scheduler
> Affects Versions: 2.0.0
> Reporter: Josh Rosen
> Assignee: Jiang Xingbo
> Fix For: 2.3.0
>
>
> In SPARK-17370 (a patch authored by [~ekhliang] and reviewed by me), we added
> logic to the DAGScheduler to mark external shuffle service instances as
> unavailable upon task failure when the task failure reason was "SlaveLost"
> and this was known to be caused by worker death. If the Spark Master
> discovered that a worker was dead then it would notify any drivers with
> executors on those workers to mark those executors as dead. The linked patch
> simply piggybacked on this logic to have the executor death notification also
> imply worker death and to have worker-death-caused-executor-death imply
> shuffle file loss.
> However, there are modes of external shuffle service loss which this
> mechanism does not detect, leaving the system prone race conditions. Consider
> the following:
> * Spark standalone is configured to run an external shuffle service embedded
> in the Worker.
> * Application has shuffle outputs and executors on Worker A.
> * Stage depending on outputs of tasks that ran on Worker A starts.
> * All executors on worker A are removed due to dying with exceptions,
> scaling-down via the dynamic allocation APIs, but _not_ due to worker death.
> Worker A is still healthy at this point.
> * At this point the MapOutputTracker still records map output locations on
> Worker A's shuffle service. This is expected behavior.
> * Worker A dies at an instant where the application has no executors running
> on it.
> * The Master knows that Worker A died but does not inform the driver (which
> had no executors on that worker at the time of its death).
> * Some task from the running stage attempts to fetch map outputs from Worker
> A but these requests time out because Worker A's shuffle service isn't
> available.
> * Due to other logic in the scheduler, these preventable FetchFailures don't
> wind up invaliding the now-invalid unavailable map output locations (this is
> a distinct bug / behavior which I'll discuss in a separate JIRA ticket).
> * This behavior leads to several unsuccessful stage reattempts and ultimately
> to a job failure.
> A simple way to address this would be to have the Master explicitly notify
> drivers of all Worker deaths, even if those drivers don't currently have
> executors. The Spark Standalone scheduler backend can receive the explicit
> WorkerLost message and can bubble up the right calls to the task scheduler
> and DAGScheduler to invalidate map output locations from the now-dead
> external shuffle service.
> This relates to SPARK-20115 in the sense that both tickets aim to address
> issues where the external shuffle service is unavailable. The key difference
> is the mechanism for detection: SPARK-20115 marks the external shuffle
> service as unavailable whenever any fetch failure occurs from it, whereas the
> proposal here relies on more explicit signals. This JIRA ticket's proposal is
> scoped only to Spark Standalone mode. As a compromise, we might be able to
> consider "all of a single shuffle's outputs lost on a single external shuffle
> service" following a fetch failure (to be discussed in separate JIRA).
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