[jira] [Commented] (IMPALA-7561) Expired queries should end up in a consistent state (EXCEPTION, CANCELLED, or something else)

["Tim Armstrong (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/IMPALA-7561?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16786230#comment-16786230 ] 

Tim Armstrong commented on IMPALA-7561:
---------------------------------------

I ran into this while working on the stress test - it's very natural to write a loop that polls for the status to be either EXCEPTION or CANCELED when you're expected EXEC_TIME_LIMIT_S to kick in.

> Expired queries should end up in a consistent state (EXCEPTION, CANCELLED, or something else)
> ---------------------------------------------------------------------------------------------
>
>                 Key: IMPALA-7561
>                 URL: https://issues.apache.org/jira/browse/IMPALA-7561
>             Project: IMPALA
>          Issue Type: Improvement
>          Components: Backend
>            Reporter: Tim Armstrong
>            Priority: Major
>              Labels: query-lifecycle
>
> ClientRequestState treats "eos" as a terminal state and won't transition to EXCEPTION or CANCELLED out of it. See the below code snippet from ClientRequestState::Cancel():
> {code}
>     bool already_done = eos_ || operation_state_ == TOperationState::ERROR_STATE;
>     if (!already_done && cause != NULL) {
>       DCHECK(!cause->ok());
>       discard_result(UpdateQueryStatus(*cause));
>       query_events_->MarkEvent("Cancelled");
>       DCHECK_EQ(operation_state_, TOperationState::ERROR_STATE);
>     }
> {code}
> If the cancellation is initiated by the server (e.g. because of query_timeout_s or exec_time_limit_s) then we should arguably treat that as an exception and put the query into the EXCEPTION state (because it is not a user-initiated cancellation) if it is not already in an EXCEPTION or CANCELLED state. That way the client can see that the expiry happened and access the cause of expiry.
> One argument against using the EXCEPTION state is that admins or users might think that something went wrong and needs to be investigated, see IMPALA-471.
> A separate issue is that user-initiated cancellation should use the CANCELLED state: IMPALA-1262



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