Github user sihuazhou commented on the issue:
https://github.com/apache/flink/pull/5490
Aha, I got it. But I also found the description of Memory state backend is
wrong in these PR, the description is `The MemoryStateBackend can be configured
to use asynchronous snapshots. While we strongly encourage the use of
asynchronous snapshots to avoid blocking pipelines, please note that this is a
new feature and currently not enabled by default.`, but I found `asynchronous
snapshots` is enabled by default, it seems like out of date, could you please
also have a look ? @StefanRRichter
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