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https://issues.apache.org/jira/browse/NIFI-4775?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16902210#comment-16902210
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Brandon DeVries commented on NIFI-4775:
---------------------------------------
Submitted patch, and attached documentation as adoc and html. The
documentation should possibly be incorporated into the existing documentation,
but I wanted to allow for general review first. Also, I'm reasonably sure
there are no licensing issues, but I would appreciate anyone else checking as
well.
> Allow FlowFile Repository to optionally perform fsync when writing CREATE
> events but not other events
> -----------------------------------------------------------------------------------------------------
>
> Key: NIFI-4775
> URL: https://issues.apache.org/jira/browse/NIFI-4775
> Project: Apache NiFi
> Issue Type: Improvement
> Components: Core Framework
> Reporter: Mark Payne
> Assignee: Brandon DeVries
> Priority: Major
> Attachments: RocksDBFlowFileRepo.html, rocksdb-flowfile-repo.adoc
>
> Time Spent: 10m
> Remaining Estimate: 0h
>
> Currently, when a FlowFile is written to the FlowFile Repository, the repo
> can either fsync or not, depending on nifi.properties. We should allow a
> third option, of fsync only for CREATE events. In this case, if we receive
> new data from a source we can fsync the update to the FlowFile Repository
> before ACK'ing the data from the source. This allows us to guarantee data
> persistence without the overhead of an fsync for every FlowFile Repository
> update.
> It may make sense, though, to be a bit more selective about when do this. For
> example if the source is a system that does not allow us to acknowledge the
> receipt of data, such as a ListenUDP processor, this doesn't really buy us
> much. In such a case, we could be smart about avoiding the high cost of an
> fsync. However, for something like GetSFTP where we have to remove the file
> in order to 'acknowledge receipt' we can ensure that we wait for the fsync
> before proceeding.
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