[jira] [Commented] (HIVE-17641) Visibility issue of Task.done cause Driver skip stages in parallel execution

["Ashutosh Chauhan (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-17641?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16189057#comment-16189057 ] 

Ashutosh Chauhan commented on HIVE-17641:
-----------------------------------------

+1

> Visibility issue of Task.done cause Driver skip stages in parallel execution
> ----------------------------------------------------------------------------
>
>                 Key: HIVE-17641
>                 URL: https://issues.apache.org/jira/browse/HIVE-17641
>             Project: Hive
>          Issue Type: Bug
>    Affects Versions: 0.14.1
>            Reporter: Zhiyuan Yang
>            Assignee: Zhiyuan Yang
>         Attachments: HIVE-17641.1-branch-0.14.patch, HIVE-17641.2-branch-0.14.patch
>
>
> Task.done is not volatile. In case of parallel execution, TaskRunner thread set this value, and Driver thread read this value when it determines whether a child task is runnable
> DriverContext.java
> {code}
> public static boolean isLaunchable(Task<? extends Serializable> tsk) {
>     return !tsk.getQueued() && !tsk.getInitialized() && tsk.isRunnable();
> {code}
> Task.java
> {code}
> public boolean isRunnable() {
>     boolean isrunnable = true;
>     if (parentTasks != null) {
>       for (Task<? extends Serializable> parent : parentTasks) {
>         if (!parent.done()) {
> {code}
> This happens without any synchronization, so a child can be not runnable even all parents finish.
> To make it worse, Driver think query is successful when there is no running task or runnable task, so query may finish without executing some stages.
> Driver.java
> {code}
> while (!destroyed && driverCxt.isRunning()) {
> {code}
> DriverContext.java
> {code}
> public synchronized boolean isRunning() {
>     return !shutdown && (!running.isEmpty() || !runnable.isEmpty());
> {code}



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