hi Good morning, afternoon and evening, i have a question on

EventTimeTrigger

from flink

@Override
    public TriggerResult onElement(
            Object element, long timestamp, TimeWindow window, TriggerContext ctx)
            throws Exception {
        if (window.maxTimestamp() <= ctx.getCurrentWatermark()) {
            // if the watermark is already past the window fire immediately
            return TriggerResult.FIRE;
        } else {
            ctx.registerEventTimeTimer(window.maxTimestamp());
            return TriggerResult.CONTINUE;
        }
    }

suppose there are 5 elements of a same window got into

onElement

function and hit the

registerEventTimeTimer

five times, will the

onEventTime

get invoke 5 times ?

It depends on the type of window. If the trigger is working on say, a

TumblingWindow

which has a fixed start and end,

window.maxTimestamp()

will be the same for all 5 elements in the window so

onEventTime

will be called only once. For a

SessionWindow

which gets extended if it receives an element within a certain time,

onEventTime

can be invoked up to 5 times. If the 5 events arrive in order and the timestamps are all different then

onEventTime

will be invoked 5 times.

thanks Elphas for the detail explanation with example