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Posted to issues@flink.apache.org by "ASF GitHub Bot (JIRA)" <ji...@apache.org> on 2016/04/26 22:56:12 UTC
[jira] [Commented] (FLINK-3257) Add Exactly-Once Processing
Guarantees in Iterative DataStream Jobs
[ https://issues.apache.org/jira/browse/FLINK-3257?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15258904#comment-15258904 ]
ASF GitHub Bot commented on FLINK-3257:
---------------------------------------
Github user senorcarbone commented on the pull request:
https://github.com/apache/flink/pull/1668#issuecomment-214883298
ok good to know @uce! Let me get back to it in a couple of weeks and make it right, now it is a bit impossible to find time.
> Add Exactly-Once Processing Guarantees in Iterative DataStream Jobs
> -------------------------------------------------------------------
>
> Key: FLINK-3257
> URL: https://issues.apache.org/jira/browse/FLINK-3257
> Project: Flink
> Issue Type: Improvement
> Reporter: Paris Carbone
> Assignee: Paris Carbone
>
> The current snapshotting algorithm cannot support cycles in the execution graph. An alternative scheme can potentially include records in-transit through the back-edges of a cyclic execution graph (ABS [1]) to achieve the same guarantees.
> One straightforward implementation of ABS for cyclic graphs can work as follows along the lines:
> 1) Upon triggering a barrier in an IterationHead from the TaskManager start block output and start upstream backup of all records forwarded from the respective IterationSink.
> 2) The IterationSink should eventually forward the current snapshotting epoch barrier to the IterationSource.
> 3) Upon receiving a barrier from the IterationSink, the IterationSource should finalize the snapshot, unblock its output and emit all records in-transit in FIFO order and continue the usual execution.
> --
> Upon restart the IterationSource should emit all records from the injected snapshot first and then continue its usual execution.
> Several optimisations and slight variations can be potentially achieved but this can be the initial implementation take.
> [1] http://arxiv.org/abs/1506.08603
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