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https://issues.apache.org/jira/browse/FLINK-9940?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17183087#comment-17183087
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Kostas Kloudas commented on FLINK-9940:
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Hi [~Averell]and [~maguowei]
Thanks for the discussion! My contribution to the discussion is the following:
1. with the
[FLIP-27|https://cwiki.apache.org/confluence/display/FLINK/FLIP-27%3A+Refactor+Source+Interface]
effort now being part of the master branch, soon many of the sources
(including the File Source) will be re-implemented based on the new APIs. This
may be a point to consider when deciding how much time we want to spend on the
problem.
2. I think that the solution of the {{READ_CONSISTENCY_OFFSET_INTERVAL}} which
stores files within this interval in state is actually a good solution. It
exposes the tradeoff between accuracy and required storage space to the user
and with good documentation it can actually lead to a good user experience. In
addition, it makes no assumptions about the user's set-up.
I have not looked at the code yet. But if we all agree that this is the
solution we want to go with until a new File Source comes, I can have a look.
> File source continuous monitoring mode: S3 files sometimes missed
> -----------------------------------------------------------------
>
> Key: FLINK-9940
> URL: https://issues.apache.org/jira/browse/FLINK-9940
> Project: Flink
> Issue Type: Bug
> Components: API / DataStream
> Affects Versions: 1.5.1
> Environment: Flink 1.5, EMRFS
> Reporter: Huyen Levan
> Assignee: Huyen Levan
> Priority: Major
> Labels: EMRFS, Flink, S3, pull-request-available
>
> When using StreamExecutionEnvironment.readFile() with
> FileProcessingMode.PROCESS_CONTINUOUSLY mode to monitor an S3 prefix, if
> there is a high amount of new/modified files at the same time, the directory
> monitoring process might miss some files. The number of missing files depends
> on the monitoring interval.
> Cause: Flink tracks which files it has read by remembering the modification
> time of the file that was added (or modified) last. So when there are
> multiple files having a same last-modified timestamp.
> Suggested solution (thanks to [[Fabian
> Hueske|http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/template/NamlServlet.jtp?macro=user_nodes&user=25]|http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/template/NamlServlet.jtp?macro=user_nodes&user=25]):
> a hybrid approach that keeps the names of all files that have a mod
> timestamp that is larger than the max mod time minus an offset.
> _org.apache.flink.streaming.api.functions.source.ContinuousFileMonitoringFunction_
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