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Chandni Singh commented on APEXMALHAR-2223:
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A possible approach to address this:
- Have a property in ManagedState called {code}writeBufferThreshold{code}. When
a bucket size crosses this threshold, then the bucket is eligible for writing.
- The writing to WAL of eligible buckets is done at the end of every
application window() in {code}endWindow(){code} callback.
With this approach there are fewer changes where data is still divided into
windows when written to the WAL.
> 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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