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https://issues.apache.org/jira/browse/KUDU-3747?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Alexey Serbin updated KUDU-3747:
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Attachment: repro.cc
> Clarify on the C++ client meta-cache logic for
> create-table-and-immediate-write-and-scan use case
> -------------------------------------------------------------------------------------------------
>
> Key: KUDU-3747
> URL: https://issues.apache.org/jira/browse/KUDU-3747
> Project: Kudu
> Issue Type: Task
> Components: client
> Affects Versions: 1.13.0, 1.14.0, 1.15.0, 1.16.0, 1.17.0, 1.18.0, 1.17.1,
> 1.18.1
> Reporter: Alexey Serbin
> Priority: Major
> Attachments: repro.cc
>
>
> With KUDU-1802 implemented, the Kudu C++ client is able to obtain information
> on tablet replica locations from scan tokens, avoiding extra calls to Kudu
> masters when such information in present. It works very well in the majority
> of use cases. However, a couple of surprises were discovered in a relatively
> rare use case when a Kudu client application creates a new table, immediately
> start writing data into the newly created table, and then reads data back
> from the table.
> The two unexpected items are:
> # After populating its metacache with the information on the location of
> tablet replicas and using it while writing data into the newly created table,
> the client still calls {{KuduClient::Data::GetTabletServer()}} as a part of
> {{KuduScanner::Data::OpenTablet()}} when commencing read/scan operation.
> # Even if ignoring the already existing tablet location information in the
> metacache (say, if it's short-lived and already expired), it would be natural
> for the client at least to rely on the information in the scan tokens when
> opening a table for scanning (given KUDU-1802 provisions are already there)
> instead of re-resolving tablet locations.
> This became apparent once increasing the setting for the
> {{\-\-raft_heartbeat_interval_ms}} setting that Kudu tablet servers run
> tenfold (i.e. from default 500 ms to 5000 ms): the client application that
> tries to exercise the described use case exhibited high latency when calling
> {{KuduScanner::Open()}} right after writing a few rows into the newly created
> table.
> It's necessary to clarify what's going on.
> Attached is a sample Kudu client application in C++. Compile it similarly to
> {{$KUDU_HOME/examples/cpp/example.cc}} and run against a Kudu cluster having
> at least three tablet servers.
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