I got little confused after reading this line on this document vs white paper.
"The windowPeriod is the slack time permitted for events. For example, a windowPeriod of ten minutes (the default) means that any events with a timestamp older than ten minutes in the past, or more than ten minutes in the future, will be dropped.
My understanding on window period is that it only matters after the current segment time is elapsed. Say for example if segment 3pm to 4pm is open with window period 10 minutes.
a. If current time is 3:40 pm and I receive an event timestamped at 3:05 and window period is 10 minutes. Tranquility should still accepted the event as segment is still open.
b. If current time is 4:05 pm and I receive an event timestamped at 3:58 pm or 3:40 pm. This event should still be accepted.
c. If current time is 4:15 pm, nothing from segment 3 to 4 should be accepted as window period is complete.
It does work like you say in some cases, but technically that’s not guaranteed and may not behave like that in every release or in every setup. The thing that is guaranteed is that if an event is within windowPeriod of now, then it will be indexed. Events outside the windowPeriod, but still in a “valid” segment, may or may not be indexed.