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https://issues.apache.org/jira/browse/FLINK-2393?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14697170#comment-14697170
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Stephan Ewen commented on FLINK-2393:
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Added the documentation in 21a0c94baafd77297c8eb88367fc8caaac43d8ee
Docs describe the usage of the mode (in the streaming API docs) and the
functionality (in the internals documentation)
Docs should be accessible on the website as soon as the CI bot builds the docs
tonight.
> 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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