Flink window Trigger
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* to you under the Apache License, Version 2.0 (the
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*
* /licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
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* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.tigerclub.grassland.function;
import org.apache.flink.annotation.PublicEvolving;
import org.apache.flink.api.common.state.ValueState;
import org.apache.flink.api.common.state.ValueStateDescriptor;
import org.apache.flink.api.common.typeinfo.Types;
import org.apache.flink.streaming.api.windowing.triggers.Trigger;
import org.apache.flink.streaming.api.windowing.triggers.TriggerResult;
import org.apache.flink.streaming.api.windowing.windows.TimeWindow;
import java.io.IOException;
/**
* A {@link Trigger} that fires once the watermark passes the end of the window
* to which a pane belongs.
*
* @see
*/
@PublicEvolving
public class EventTimeOrIntervalTrigger extends Trigger<Object, TimeWindow> {
private static final long serialVersionUID = 1L;
ValueStateDescriptor<Integer> triggerStateDescriptor;
public EventTimeOrIntervalTrigger(String instanceId) {
triggerStateDescriptor = new ValueStateDescriptor<Integer>("triggerState" + instanceId, Types.INT);
}
@Override
public TriggerResult onElement(Object element, long timestamp, TimeWindow window, TriggerContext ctx) throws Exception {
ValueState<Integer> triggerState = ctx.getPartitionedState(triggerStateDescriptor);
Integer state = triggerState.value();
if (state == null) {// first element in this window
long processTriggerTime = ctx.getCurrentProcessingTime() + (long) ((window.getEnd() - window.getStart()) * 1.2);
ctx.registerProcessingTimeTimer(processTriggerTime);
ctx.registerEventTimeTimer(window.maxTimestamp());
triggerState.update(1);
return TriggerResult.CONTINUE;
}
if (window.maxTimestamp() <= ctx.getCurrentWatermark()) {
// if the watermark is already past the window fire immediately
return TriggerResult.FIRE;
}
return TriggerResult.CONTINUE;
}
@Override
public TriggerResult onEventTime(long time, TimeWindow window, TriggerContext ctx) throws IOException {
if (time == window.maxTimestamp()) {
ValueState<Integer> triggerState = ctx.getPartitionedState(triggerStateDescriptor);
if (triggerState.value() != null && triggerState.value() != 2) {
triggerState.update(3);
return TriggerResult.FIRE;
}
}
return TriggerResult.CONTINUE;
}
@Override
public TriggerResult onProcessingTime(long time, TimeWindow window, TriggerContext ctx) throws Exception {
ValueState<Integer> triggerState = ctx.getPartitionedState(triggerStateDescriptor);
if (triggerState != null && triggerState.value() != 3) {
triggerState.update(2);
return TriggerResult.FIRE_AND_PURGE;
} else {
return TriggerResult.CONTINUE;
}
}
@Override
public void clear(TimeWindow window, TriggerContext ctx) throws Exception {
ctx.deleteEventTimeTimer(window.maxTimestamp());
}
@Override
public boolean canMerge() {
return true;
}
@Override
public void onMerge(TimeWindow window,
OnMergeContext ctx) {
// only register a timer if the watermark is not yet past the end of the merged window
// this is in line with the logic in onElement(). If the watermark is past the end of
// the window onElement() will fire and setting a timer here would fire the window twice.
long windowMaxTimestamp = window.maxTimestamp();
if (windowMaxTimestamp > ctx.getCurrentWatermark()) {
ctx.registerEventTimeTimer(windowMaxTimestamp);
}
}
@Override
public String toString() {
return "EventTimeTrigger()";
}
/**
* Creates an event-time trigger that fires once the watermark passes the end of the window.
*
* <p>Once the trigger fires all elements are discarded. Elements that arrive late immediately
* trigger window evaluation with just this one element.
*/
public static EventTimeOrIntervalTrigger create(String instanceId) {
return new EventTimeOrIntervalTrigger(instanceId);
}
}