Re: Question about the checkpoint mechanism in Flink.

Posted by Renjie Liu on
URL: http://deprecated-apache-flink-user-mailing-list-archive.369.s1.nabble.com/Question-about-the-checkpoint-mechanism-in-Flink-tp9792p9799.html

Sorry the incorrect reply, please ignore this.

On Tue, Nov 1, 2016 at 8:47 PM Renjie Liu <[hidden email]> wrote:

Essentially you are right, but the snapshot commit process is asynchronous. That's what you have to pay for exactly once semantics.

Li Wang <[hidden email]>于2016年11月1日周二 下午3:05写道：

Hi all,

I have a question regarding to the state checkpoint mechanism in Flink. I find the statement  "Once the last stream has received barrier n, the operator emits all pending outgoing records, and then emits snapshot n barriers itself” on the document https://ci.apache.org/projects/flink/flink-docs-master/internals/stream_checkpointing.html#exactly-once-vs-at-least-once.

Does this mean that to achieve exactly-once semantic, instead of sending tuples downstream immediately the operator buffers its outgoing tuples in a pending queue until the current snapshot is committed? If yes, will this introduce significant processing delay?

Thanks,

Li

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