Nico Kruber created FLINK-9107:
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Summary: Document timer coalescing for ProcessFunctions
Key: FLINK-9107
URL: https://issues.apache.org/jira/browse/FLINK-9107
Project: Flink
Issue Type: Improvement
Components: Documentation, Streaming
Affects Versions: 1.4.0, 1.3.0, 1.5.0, 1.6.0
Reporter: Nico Kruber
Assignee: Nico Kruber
Fix For: 1.5.0, 1.4.3, 1.3.4
In a {{ProcessFunction}}, registering timers for each event via
{{ctx.timerService().registerEventTimeTimer()}} using times like
{{ctx.timestamp() + timeout}} will get a millisecond accuracy and may thus
create one timer per millisecond which may lead to some overhead in the
{{TimerService}}.
This problem can be mitigated by using timer coalescing if the desired accuracy
of the timer can be larger than 1ms. A timer firing at full seconds only, for
example, can be realised like this:
{code}
coalescedTime = ((ctx.timestamp() + timeout) / 1000) * 1000;
ctx.timerService().registerEventTimeTimer(coalescedTime);
{code}
As a result, only a single timer may exist for every second since we do not add
timers for timestamps that are already there.
This should be documented in the {{ProcessFunction}} docs.
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