switch event time to process time

[venn wu <ve...@gmail.com>]

Dear experts:

            My  flink job work with event time, but I  have a trouble, the
source even will be very few at the early morning, can't finish current
widow and emitted the result as expect.  I found the next paragraph at
official website. How can I “switches to using current processing time as
the time basis after not observing new events for a while” ?



https://ci.apache.org/projects/flink/flink-docs-release-1.9/dev/event_time.html#idling-sources

 “

*Currently, with pure event time watermarks generators, watermarks can not
progress if there are no elements to be processed. That means in case of
gap in the incoming data, event time will not progress and for example the
window operator will not be triggered and thus existing windows will not be
able to produce any output data.*

*To circumvent this one can use periodic watermark assigners that don’t
only assign based on element timestamps. An example solution could be an
assigner that switches to using current processing time as the time basis
after not observing new events for a while.*

*Sources can be marked as idle using *
*SourceFunction.SourceContext#markAsTemporarilyIdle**. For details please
refer to the Javadoc of this method as well as **StreamStatus**.*

”


Thanks