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From Zhangrucong <zhangruc...@huawei.com>
Subject Question about exactly-once
Date Tue, 08 Sep 2015 05:05:40 GMT
Dear Sir:
I am a beginner of Flink and very interested in “Exactly-once” Recovery Mechanism. I have
a question about processing sequence problem of tuples. For example, in Fig 1, process unit
A runs JOIN, and the size of sliding window is 4. At the beginning, the state of sliding windows
is shown in Fig 2. Before A failed, Tuples came in the order of 1,2,3,4,and the join results
are (1,1),(2,2)(2,2)(3,3)(4,4),but after A failed and the state is reset to Snap(x), tuples
came in the order of 3,4,1,2. This time the join results are (3,3)(3,3)(4,4)(2,2)(2,2).
[cid:image001.png@01D0EA37.0E67AA00]
Fig 1
[cid:image002.png@01D0EA37.0E67AA00]
Fig 2
I wonder how Flink’s mechanism guarantees the consistency of results or consistency of tuples’
sequence?


Thank you very much.
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