[jira] [Resolved] (IMPALA-6735) Inconsistent query submission, start, and end times in query profile

["Alexander Behm (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/IMPALA-6735?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Alexander Behm resolved IMPALA-6735.
------------------------------------
    Resolution: Not A Bug

> Inconsistent query submission, start, and end times in query profile
> --------------------------------------------------------------------
>
>                 Key: IMPALA-6735
>                 URL: https://issues.apache.org/jira/browse/IMPALA-6735
>             Project: IMPALA
>          Issue Type: Bug
>          Components: Backend
>    Affects Versions: Impala 2.11.0
>            Reporter: Alexander Behm
>            Priority: Major
>              Labels: supportability
>
> We've sometimes observed inconsistencies in the following runtime profile entrues:
> * Query submitted (timeline event)
> * Start Time (info string, not a timeline event)
> * End Time (into string, not a timeline event)
> Here is one inconsistent example:
> {code}
> Query submitted at	: 2018-03-22 10:27:57
> Start Time	: 2018-03-22 10:28:05.883997000 
> End Time	: 2018-03-22 10:28:05.915566000
> {code}
> Based on the backend code it should not be possible that "Start Time" happens after "Query submitted". The relevant code snipped is in impala-server.cc ImpalaServer::ExecuteInternal():
> {code}
> ...
> // Sets the Start Time
>   request_state->reset(new ClientRequestState(query_ctx, exec_env_, exec_env_->frontend(),
>       this, session_state));
> // Sets the query submitted time
>   (*request_state)->query_events()->MarkEvent("Query submitted");
> ...
> {code}
> One possible explanation could be that these events get the current time from different functions:
> * The timeline events use our MonotonicStopWatch
> * The "Start Time" and "End Time" use UnixMicros() from our own time.h
> It's not clear that these produce consistent timings.



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