Github user dyanarose commented on a diff in the pull request:
https://github.com/apache/flink/pull/5295#discussion_r161807837
--- Diff:
flink-streaming-java/src/main/java/org/apache/flink/streaming/api/windowing/assigners/DynamicEventTimeSessionWindows.java
---
@@ -0,0 +1,101 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.streaming.api.windowing.assigners;
+
+import org.apache.flink.api.common.ExecutionConfig;
+import org.apache.flink.api.common.typeutils.TypeSerializer;
+import
org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
+import org.apache.flink.streaming.api.windowing.triggers.Trigger;
+import
org.apache.flink.streaming.api.windowing.triggers.TypedEventTimeTrigger;
+import org.apache.flink.streaming.api.windowing.windows.TimeWindow;
+
+import java.util.Collection;
+import java.util.Collections;
+
+/**
+ * A {@link WindowAssigner} that windows elements into sessions based on
the timestamp of the
+ * elements. Windows cannot overlap.
+ *
+ * <p>For example, in order to window into windows with a dynamic time gap:
+ * <pre> {@code
+ * DataStream<Tuple2<String, Integer>> in = ...;
+ * KeyedStream<String, Tuple2<String, Integer>> keyed = in.keyBy(...);
+ * WindowedStream<Tuple2<String, Integer>, String, TimeWindows> windowed =
+ * keyed.window(DynamicEventTimeSessionWindows.withDynamicGap({@link
SessionWindowTimeGapExtractor }));
+ * } </pre>
+ *
+ * @param <T> The type of the input elements
+ */
+public class DynamicEventTimeSessionWindows<T> extends
MergingWindowAssigner<T, TimeWindow> {
+ private static final long serialVersionUID = 1L;
+
+ protected SessionWindowTimeGapExtractor<T>
sessionWindowTimeGapExtractor;
+
+ protected
DynamicEventTimeSessionWindows(SessionWindowTimeGapExtractor<T>
sessionWindowTimeGapExtractor) {
+ this.sessionWindowTimeGapExtractor =
sessionWindowTimeGapExtractor;
+ }
+
+ @Override
+ public Collection<TimeWindow> assignWindows(T element, long timestamp,
WindowAssignerContext context) {
+ long sessionTimeout =
sessionWindowTimeGapExtractor.extract(element, timestamp, context);
+ if (sessionTimeout <= 0) {
+ throw new IllegalArgumentException("Dynamic session
time gap must satisfy 0 < gap");
+ }
+ return Collections.singletonList(new TimeWindow(timestamp,
timestamp + sessionTimeout));
+ }
+
+ @Override
+ public Trigger<T, TimeWindow>
getDefaultTrigger(StreamExecutionEnvironment env) {
+ return TypedEventTimeTrigger.create();
--- End diff --
as above
---
