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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-5963) Canceling a query hung in planning state, leaves the query in ENQUEUED state for ever.
Date Mon, 27 Nov 2017 21:50:02 GMT

    [ https://issues.apache.org/jira/browse/DRILL-5963?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16267629#comment-16267629
] 

ASF GitHub Bot commented on DRILL-5963:
---------------------------------------

Github user ppadma commented on a diff in the pull request:

    https://github.com/apache/drill/pull/1051#discussion_r153278034
  
    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/work/foreman/Foreman.java
---
    @@ -221,11 +200,15 @@ public QueryManager getQueryManager() {
       }
     
       /**
    -   * Cancel the query. Asynchronous -- it may take some time for all remote fragments
to be
    -   * terminated.
    +   * Cancel the query. Asynchronous -- it may take some time for all remote fragments
to be terminated.
    +   * For planning and enqueued states we cancel immediately since these states are done
locally.
    +   *
    +   * Note this can be called from outside of run() on another thread, or after run()
completes
        */
       public void cancel() {
    -    // Note this can be called from outside of run() on another thread, or after run()
completes
    +    if (QueryState.PLANNING == state || QueryState.ENQUEUED == state) {
    +      moveToState(QueryState.CANCELLATION_REQUESTED, null);
    --- End diff --
    
    Please add a comment explaining why you are moving to CANCELLATION_REQUESTED state only
when query is in  PLANNING and ENQUEUED states. For ex., why not PREPARING State ?


> Canceling a query hung in planning state, leaves the query in ENQUEUED state for ever.
> --------------------------------------------------------------------------------------
>
>                 Key: DRILL-5963
>                 URL: https://issues.apache.org/jira/browse/DRILL-5963
>             Project: Apache Drill
>          Issue Type: Bug
>          Components: Execution - Flow
>    Affects Versions: 1.12.0
>         Environment: Drill 1.12.0-SNAPSHOT, commit: 4a718a0bd728ae02b502ac93620d132f0f6e1b6c
>            Reporter: Khurram Faraaz
>            Assignee: Arina Ielchiieva
>            Priority: Critical
>             Fix For: 1.13.0
>
>         Attachments: enqueued-2.png
>
>
> Canceling the below query that is hung in planning state, leaves the query in ENQUEUED
state for ever.
> Here is the query that is hung in planning state
> {noformat}
> 0: jdbc:drill:schema=dfs.tmp> select 1 || ',' || 2 || ',' || 3 || ',' || 4 || ','
|| 5 || ',' || 6 || ',' || 7 || ',' || 8 || ',' || 9 || ',' || 0 || ',' AS CSV_DATA from (values(1));
> +--+
> |  |
> +--+
> +--+
> No rows selected (304.291 seconds)
> {noformat}
> Explain plan for that query also just hangs.
> {noformat}
> explain plan for select 1 || ',' || 2 || ',' || 3 || ',' || 4 || ',' || 5 || ',' || 6
|| ',' || 7 || ',' || 8 || ',' || 9 || ',' || 0 || ',' AS CSV_DATA from (values(1));
> ...
> {noformat}
> The above issues show the following problems:
> *1. Simple query with reasonable number of concat functions hangs.*
> In reality query does not hang it just take lots of time to execute. The root cause is
that during planning time DrillFuncHolderExpr return type is extensively used to determine
matching function, matching type etc. Though this type is retrieved via [getter|https://github.com/apache/drill/blob/master/exec/java-exec/src/main/java/org/apache/drill/exec/expr/DrillFuncHolderExpr.java#L41]
in reality complex logic is executed beaneath it. For example for [concat function|https://github.com/apache/drill/blob/master/exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/output/ConcatReturnTypeInference.java#L47].
Since function return type can not be changes during DrillFuncHolderExpr life time, it is
safe to cache it.
> *2. No mechanism to cancel query during ENQUEUED state.*
> Currently Drill does not have mechanism to cancel query before STARTING / RUNNING states.
Plus ENQUEUED state includes two PLANNING and ENQUEUED.
> Also submitting mechanism for submitting query to the queue is blocking, making foreman
wait till enqueueing is done Making it non-blocking will prevent consuming threads that just
sit idle in a busy system and also is important when we move to a real admission control solution.
> The following changes were made to address above issues:
> a. two new states were added: PREPARING (when foreman is initialized) and PLANNING (includes
logical and / or physical planning).
> b. process of query enqueuing was made non-blocking. Once query was enqueued, fragments
runner is called to submit fragments locally and remotely.
> c. ability to cancel query during planning and enqueued states was added.



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