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https://issues.apache.org/jira/browse/NIFI-1484?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15135879#comment-15135879
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Joe Skora commented on NIFI-1484:
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Similar to the way ListHDFS works, ListFILE tracks the files seen with the
latest timestamp so that if the listing was pulled while a batch of files is
being written by the OS, new files with the same timestamp will not be skipped
the next time the processor scans the directory.
So, if at Scan1 there are files A and B with timestamp T0, and files C, D, E
with T1, it selects A,B,C,D,E for processing and saves state=T1-C,D,E. When at
Scan2 there are files F with T1 and G,H with T2, it selects F,G,H and saves
state=T2-G,H.
I hope that makes sense. Saving only the timestamp will result in skipping
file F. If this approach needs to be revisited, it probably needs to be looked
at for ListHDFS as well, if not other ListXXX processors.
> ListFile holds unbounded list of files with matching time stamps
> ----------------------------------------------------------------
>
> Key: NIFI-1484
> URL: https://issues.apache.org/jira/browse/NIFI-1484
> Project: Apache NiFi
> Issue Type: Bug
> Components: Core UI, Extensions
> Affects Versions: 0.4.0, 0.5.0
> Reporter: Joseph Witt
>
> ListFile appears to hold an unbounded set of filenames that match the last
> timestamp. While this is understandable to handle the edge case of new data
> arriving at the same time it presents two problems. First we hold all of
> this information in state management which could put considerable pressure on
> both the local and remote stores but we also have it in memory before we
> persist it.
> Also, the entire state listing appears to show up in the UI without
> pagination or any limit on number of entries. This seems like a problem for
> the client-side as well. The server side should probably restrict this.
> Finally, it seems like the need for saving filenames seen at a given
> timestamp is only necessary if we're assuming the listing we do is 'as-of'
> RIGHT NOW. What is instead we did the listing based on a last modified time
> of 'RIGHTNOW'-1 millisecond or something like that? Then we should not have
> to worry at all about keeping a listing of names for the timestamp.
> The reason I think this is important is that it is not at all uncommon for a
> directory with large quantities of files to have data at the same time due to
> a copy operation not preserving original file attributes.
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