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https://issues.apache.org/jira/browse/FLINK-2393?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Stephan Ewen closed FLINK-2393.
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> Add a "stateless at-least-once" mode for streaming
> --------------------------------------------------
>
> Key: FLINK-2393
> URL: https://issues.apache.org/jira/browse/FLINK-2393
> Project: Flink
> Issue Type: New Feature
> Components: Streaming
> Affects Versions: 0.10
> Reporter: Stephan Ewen
> Assignee: Stephan Ewen
> Fix For: 0.10
>
>
> Currently, the checkpointing mechanism provides "exactly once" guarantees.
> Part of that is the step that temporarily "aligns" the data streams. This
> step increases the tuple latency temporarily.
> By offering a version that does not provide "exactly-once", but only
> "at-least-once", we can avoid the latency increase. For super-low-latency
> applications, that tolerate duplicates, this may be an interesting option.
> To realize that, we would use a slightly modified version of the
> checkpointing algorithm. Effectively, the streams would not be aligned, but
> tasks would only count the received barriers and emit their own barrier as
> soon as the saw a barrier from all inputs.
> My feeling is that it makes not sense to implement state backups, when being
> concerned with this super low latency. The mode would hence be a purely
> stateless at-least-once mode.
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