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https://issues.apache.org/jira/browse/IMPALA-12014?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17703786#comment-17703786
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Alexey Serbin edited comment on IMPALA-12014 at 3/22/23 8:35 PM:
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{quote}
Warnings aren't really application-friendly. Would it be possible to output the
warning as part of the iterator error?
{quote}
I guess it's possible to output any warnings that were accumulated during the
lifetime of a scanner wrapper in impalad code if storing those as a part of the
scanner wrapper's state. However, those might be irrelevant and/or misleading
because the root cause of the error could be unrelated (same for the warnings
in the logs).
Do we want to show those to the end-user even if it's not possible to tell
whether they are relevant or not to the error that ended the query?
was (Author: aserbin):
{quote}
Warnings aren't really application-friendly. Would it be possible to output the
warning as part of the iterator error?
{quote}
I guess it's possible to output any warnings that were accumulated during the
lifetime of a scanner wrapper in impalad code if storing those as a part of the
scanner wrapper's state. However, those might be irrelevant and/or misleading
because the root cause of the error could be unrelated (same for the warnings
in the logs).
> Output a warning message on failed KeepAlive RPC for a Kudu scanner
> -------------------------------------------------------------------
>
> Key: IMPALA-12014
> URL: https://issues.apache.org/jira/browse/IMPALA-12014
> Project: IMPALA
> Issue Type: Improvement
> Components: Backend, be
> Affects Versions: Impala 2.7.0, Impala 2.8.0, Impala 2.7.1, Impala 2.9.0,
> Impala 2.10.0, Impala 2.11.0, Impala 3.0, Impala 2.12.0, Impala 3.1.0, Impala
> 3.2.0, Impala 4.0.0, Impala 3.3.0, Impala 3.4.0, Impala 3.4.1, Impala 4.1.0,
> Impala 4.0.1, Impala 4.2.0, Impala 4.1.1
> Reporter: Alexey Serbin
> Assignee: Alexey Serbin
> Priority: Minor
> Labels: supportability, troubleshooting
> Fix For: Impala 4.3.0
>
>
> With [IMPALA-3292|https://issues.apache.org/jira/browse/IMPALA-3292], the
> code has been modified to ignore failed KeepAlive RPCs for Kudu scanners
> because one of the follow-up KeepAlive RPCs usually succeeds within TTL for
> an idle Kudu scanner.
> However, if a Kudu tablet server had been busy for a long time, it might
> happen that all the consecutive KeepAlive requests failed as well (e.g., if
> the RPC queue stayed full for the whole interval of the scanner TTL). If so
> happened, the corresponding Impala query would fail with an error message in
> the Impala's query profile like below:
> {noformat}
> ...
> Query Type: QUERY
> Query State: EXCEPTION
> Impala Query State: ERROR
> Query Status: Unable to advance iterator for node with id '1' for Kudu
> table 'mega_table': Not found: Scanner 4235dd17eb444a36a945f003c23dcf81 not
> found (it may have expired)
> ...
> {noformat}
> Without a warning message logged by impalad or other clues it's hard to infer
> the root cause of such a situation for people who have not much knowledge of
> the Kudu specifics.
> It would be great to at least log a warning message about failed attempts to
> send KeepAlive RPC for Kudu scanners. As of now, the message is logged with
> {{VLOG(1)}} facility, but verbose logging isn't usually enabled by default
> for impalad.
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