Andrey Zagrebin created FLINK-10831:
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Summary: Consider making processing time monotonically increasing
by default
Key: FLINK-10831
URL: https://issues.apache.org/jira/browse/FLINK-10831
Project: Flink
Issue Type: Improvement
Reporter: Andrey Zagrebin
At the moment, the processing time is basically implemented in a fixed way as
System.currentTimeMillis() and not configurable by users.
The timestamp provided this way is not guaranteed to be monotonically
increasing. It can jump back for a while because of possible periodic
synchronisation of local clock with other more accurate system. It can be a
problem for application business logic if we say that the general notion of
time is that it always increases.
We can change SystemProcessingTimeService to emit only timestamp which is not
less than the latest emitted one, at least for current JVM process.
This change in behaviour can be also configurable if somebody e.g. relies on
rather accurate time.
Other option is that if user needs monotonic processing time then custom
processing time service should be provided as suggested in FLINK-10830.
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