[jira] [Work started] (IMPALA-14872) Don't hold query_driver_map_ lock while calling GetMaxBackendStateLagMs

["Michael Smith (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/IMPALA-14872?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Work on IMPALA-14872 started by Michael Smith.
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> Don't hold query_driver_map_ lock while calling GetMaxBackendStateLagMs
> -----------------------------------------------------------------------
>
>                 Key: IMPALA-14872
>                 URL: https://issues.apache.org/jira/browse/IMPALA-14872
>             Project: IMPALA
>          Issue Type: Bug
>    Affects Versions: Impala 4.5.0
>            Reporter: Michael Smith
>            Assignee: Michael Smith
>            Priority: Major
>
> {{query_driver_map_}} is a highly contended data structure. Accessing it acquires a lock that prevents any other query progress on queries that share a shard, and by default there are only 4 shards.
> {{GetMaxBackendStateLagMs}} acquires a lock on each {{BackendState}} object, which may also be in use (notably while sending a {{CancelQueryFInstancesRequestPB}} RPC in Cancel()), for a coordinator within {{DoFuncForAllEntries}} in https://github.com/apache/impala/blob/4.5.0/be/src/service/impala-server.cc#L2983. Let's stop doing that.



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