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https://issues.apache.org/jira/browse/HIVE-17641?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16186192#comment-16186192
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Zhiyuan Yang commented on HIVE-17641:
-------------------------------------
[~ashutoshc] Can you help review this patch? It's a one-line fix with extra
logging. Thanks!
> 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
>
>
> 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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