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https://issues.apache.org/jira/browse/KUDU-2776?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Grant Henke updated KUDU-2776:
------------------------------
Labels: backup (was: )
> Java AUTO_FLUSH_BACKGROUND behaves like "AUTO_FLUSH_FOREGROUND" when tablet
> locations are cached
> ------------------------------------------------------------------------------------------------
>
> Key: KUDU-2776
> URL: https://issues.apache.org/jira/browse/KUDU-2776
> Project: Kudu
> Issue Type: Bug
> Affects Versions: 1.9.0
> Reporter: Will Berkeley
> Priority: Major
> Labels: backup
> Attachments: image-2019-04-16-14-37-07-908.png
>
>
> !image-2019-04-16-14-37-07-908.png!
> The above piece of a Java flamegraph shows the main application thread
> {{apply}}ing operations to a {{KuduSession}} in {{AUTO_FLUSH_BACKGROUND}}
> mode. The {{doFlush}} call is meant to set up a callbacks that actually send
> the rows to Kudu and that are triggered by the fulfillment of a Deferred for
> the tablet locations. However, when the tablet locations are cached, this
> Deferred can be fulfilled basically instantly, so by the time that the
> {{apply}}ing thread calls {{addCallbacks}}, the deferred is complete, and as
> an optimization the async library executes the callbacks on the thread that
> is adding them to the fulfilled Deferred. This means the {{apply}}ing thread
> executes the code that sends rows to Kudu, which is the opposite of how
> {{AUTO_FLUSH_BACKGROUND}} is meant to work.
> We lose out on the ability to have multiple batches in flight at once, and we
> serialize the application logic, {{apply}}, and actually sending rows to Kudu.
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