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Posted to issues-all@impala.apache.org by "Alex McLintock (JIRA)" <ji...@apache.org> on 2018/11/22 17:13:00 UTC
[jira] [Commented] (IMPALA-6843) Responses to prioritizedLoad()
requests should be returned directly and not via the statestore
[ https://issues.apache.org/jira/browse/IMPALA-6843?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16696131#comment-16696131 ]
Alex McLintock commented on IMPALA-6843:
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Although this Jira issue is classified as an "improvement" it also blocks IMPALA-6671 which is described as a critical bug. is that correct? I fear that this issue is not receiving the priority it should be because it is just an "improvement".
> Responses to prioritizedLoad() requests should be returned directly and not via the statestore
> ----------------------------------------------------------------------------------------------
>
> Key: IMPALA-6843
> URL: https://issues.apache.org/jira/browse/IMPALA-6843
> Project: IMPALA
> Issue Type: Improvement
> Components: Catalog
> Affects Versions: Impala 2.11.0
> Reporter: Dimitris Tsirogiannis
> Priority: Major
> Labels: catalog, frontend, latency, perfomance
>
> Currently, when a statement (e.g. SELECT) needs to access some unloaded tables, it issues a prioritizedLoad() request to the catalog. The catalog loads the table metadata but does not respond directly to the coordinator that issued the request. Instead, the metadata for the newly loaded tables are broadcast via the statestore. The problem with this approach is that the latency of the response may vary significantly and may depend on the latencies of other unrelated metadata operations (e.g. REFRESH) that happen to be in the same topic update.
> The response to a prioritizedLoad() request should come directly to the issuing coordinator. Other coordinators will receive the metadata of the newly loaded table via the statestore.
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