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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-8384) Session Window Assigner with Dynamic Gaps
Date Wed, 24 Jan 2018 22:02:00 GMT

    [ https://issues.apache.org/jira/browse/FLINK-8384?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16338297#comment-16338297
] 

ASF GitHub Bot commented on FLINK-8384:
---------------------------------------

Github user dyanarose commented on a diff in the pull request:

    https://github.com/apache/flink/pull/5295#discussion_r163692223
  
    --- 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;
    --- End diff --
    
    changing EventTimeTrigger/ProcessingTimeTrigger would be my preference. However I was
hesitant to just go in and change the class definition. I also don't believe it *should* break
existing tests
    
    I'll give it a go and see


> Session Window Assigner with Dynamic Gaps
> -----------------------------------------
>
>                 Key: FLINK-8384
>                 URL: https://issues.apache.org/jira/browse/FLINK-8384
>             Project: Flink
>          Issue Type: Improvement
>          Components: Streaming
>            Reporter: Dyana Rose
>            Priority: Minor
>
> *Reason for Improvement*
> Currently both Session Window assigners only allow a static inactivity gap. 
> Given the following scenario, this is too restrictive:
> * Given a stream of IoT events from many device types
> * Assume each device type could have a different inactivity gap
> * Assume each device type gap could change while sessions are in flight
> By allowing dynamic inactivity gaps, the correct gap can be determined in the [assignWindows
function|https://github.com/apache/flink/blob/master/flink-streaming-java/src/main/java/org/apache/flink/streaming/api/windowing/assigners/EventTimeSessionWindows.java#L59]
by passing the element currently under consideration, the timestamp, and the context to a
user defined function. This eliminates the need to create unwieldy work arounds if you only
have static gaps.
> Dynamic Session Window gaps should be available for both Event Time and Processing Time
streams.
> (short preliminary discussion: https://lists.apache.org/thread.html/08a011c0039e826343e9be0b1bb4e0000cfc2e12976bc65f8a43ee88@%3Cdev.flink.apache.org%3E)



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