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Posted to dev@flink.apache.org by MaGuoWei <ma...@outlook.com> on 2015/07/28 03:38:28 UTC

streaming iteration

Hi,guysI am reading the code about streaming iteration.I find there is no StreamEdge the StreamIterationHead and StreamIterationTail.Why? Because the graph can't have any ring?Or any other concerns?
thanks

Re: streaming iteration

Posted by Gyula Fóra <gy...@apache.org>.

Hey,
The JobGraph that is executed cannot have cycles (due to scheduling
reasons), that's why there is no edge between the head and tail operators.

What we do instead is we add an extra source to the head and a sink to the
tail (with the same parallelism), and the feedback data is passed outside
of the graph using blocking queues.

Cheers,
Gyula

MaGuoWei <ma...@outlook.com> ezt írta (időpont: 2015. júl. 28., K, 3:39):

> Hi,guysI am reading the code about streaming iteration.I find there is no
> StreamEdge the StreamIterationHead and StreamIterationTail.Why? Because the
> graph can't have any ring?Or any other concerns?
> thanks