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https://issues.apache.org/jira/browse/KAFKA-3184?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16701422#comment-16701422
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Matthias J. Sax commented on KAFKA-3184:
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Just a side comment: RocksDB allows to "pin/freeze" a current state to protect
it from compaction. This is a light weight metadata operation. After a version
is pinned (not sure atm what the correct RocksDB term for this operation is),
the immutable SST files can be copied in the background to complete a
checkpoint.
> Add Checkpoint for In-memory State Store
> ----------------------------------------
>
> Key: KAFKA-3184
> URL: https://issues.apache.org/jira/browse/KAFKA-3184
> Project: Kafka
> Issue Type: Improvement
> Components: streams
> Reporter: Guozhang Wang
> Priority: Major
> Labels: user-experience
>
> Currently Kafka Streams does not make a checkpoint of the persistent state
> store upon committing, which would be expensive since it is "stopping the
> world" and write on disks: for example, RocksDB would require you to copy the
> file directory to make a copy naively.
> However, for in-memory stores checkpointing maybe doable in an asynchronous
> manner hence it can be done quickly. And the benefit of having intermediate
> checkpoint is to avoid restoring from scratch if standby tasks are not
> present.
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