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https://issues.apache.org/jira/browse/APEXMALHAR-2223?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15494377#comment-15494377
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Thomas Weise commented on APEXMALHAR-2223:
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Why delay writing to the WAL to endWindow? You get the best throughput by
writing the data immediately (asynchronous), unless the same key is updated
multiple times in a window.
The other question is when the WAL should be flushed (blocking). Does it need
to be in endWindow for idempotency or otherwise beforeCheckpoint()?
> Managed state should parallelize WAL writes
> -------------------------------------------
>
> Key: APEXMALHAR-2223
> URL: https://issues.apache.org/jira/browse/APEXMALHAR-2223
> Project: Apache Apex Malhar
> Issue Type: Improvement
> Affects Versions: 3.4.0
> Reporter: Thomas Weise
> Assignee: Chandni Singh
>
> Currently, data is accumulated in memory and written to the WAL on checkpoint
> only. This causes a write spike on checkpoint and does not utilize the HDFS
> write pipeline. The other extreme is writing to the WAL as soon as data
> arrives and then only flush in beforeCheckpoint. The downside of this is that
> when the same key is written many times, all duplicates will be in the WAL.
> Need to find a balances approach, that the user can potentially fine tune.
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