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https://issues.apache.org/jira/browse/FLINK-3674?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15591201#comment-15591201
]
ASF GitHub Bot commented on FLINK-3674:
---------------------------------------
Github user kl0u commented on a diff in the pull request:
https://github.com/apache/flink/pull/2570#discussion_r84234419
--- Diff:
flink-streaming-java/src/main/java/org/apache/flink/streaming/api/functions/TimelyFlatMapFunction.java
---
@@ -0,0 +1,78 @@
+/*
+ * 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.functions;
+
+import org.apache.flink.annotation.PublicEvolving;
+import org.apache.flink.api.common.functions.Function;
+import org.apache.flink.streaming.api.TimeDomain;
+import org.apache.flink.streaming.api.TimerService;
+import org.apache.flink.util.Collector;
+
+import java.io.Serializable;
+
+/**
+ * Base interface for timely flatMap functions. FlatMap functions take
elements and transform them,
+ * into zero, one, or more elements. Typical applications can be splitting
elements, or unnesting lists
+ * and arrays.
+ *
+ * <p>A {@code TimelyFlatMapFunction} can, in addition to the
functionality of a normal
+ * {@link org.apache.flink.api.common.functions.FlatMapFunction}, also set
timers and react
+ * to them firing.
+ *
+ * <pre>{@code
+ * DataStream<X> input = ...;
+ *
+ * DataStream<Y> result = input.flatMap(new MyTimelyFlatMapFunction());
+ * }</pre>
+ *
+ * @param <I> Type of the input elements.
+ * @param <O> Type of the returned elements.
+ */
+@PublicEvolving
+public interface TimelyFlatMapFunction<I, O> extends Function,
Serializable {
+
+ /**
+ * The core method of the {@code TimelyFlatMapFunction}. Takes an
element from the input data set and transforms
+ * it into zero, one, or more elements.
+ *
+ * @param value The input value.
+ * @param timerService A {@link TimerService} that allows setting
timers and querying the
+ * current time.
+ * @param out The collector for returning result values.
+ *
+ * @throws Exception This method may throw exceptions. Throwing an
exception will cause the operation
+ * to fail and may trigger recovery.
+ */
+ void flatMap(I value, TimerService timerService, Collector<O> out)
throws Exception;
+
+ /**
+ * Called when a timer set using {@link TimerService} fires.
+ *
+ * @param timestamp The timestamp of the firing timer.
+ * @param timeDomain The {@link TimeDomain} of the firing timer.
+ * @param timerService A {@link TimerService} that allows setting
timers and querying the
+ * current time.
+ * @param out The collector for returning result values.
+ *
+ * @throws Exception This method may throw exceptions. Throwing an
exception will cause the operation
+ * to fail and may trigger recovery.
+ */
+ void onTimer(long timestamp, TimeDomain timeDomain, TimerService
timerService, Collector<O> out) throws Exception ;
--- End diff --
Why not having 2 methods `onEventTime` and `onProcessingTime`? This way we
avoid the `TimeDomain` argument, and we also tell the user to think about what
he is doing in each case.
In addition, this way is similar to the APIs we expose for the Triggers and
I think it is good to have uniform APIs. Another solution would be to change
the Trigger APIs to this but this would break user code.
> Add an interface for Time aware User Functions
> ----------------------------------------------
>
> Key: FLINK-3674
> URL: https://issues.apache.org/jira/browse/FLINK-3674
> Project: Flink
> Issue Type: New Feature
> Components: Streaming
> Affects Versions: 1.0.0
> Reporter: Stephan Ewen
> Assignee: Aljoscha Krettek
>
> I suggest to add an interface that UDFs can implement, which will let them be
> notified upon watermark updates.
> Example usage:
> {code}
> public interface EventTimeFunction {
> void onWatermark(Watermark watermark);
> }
> public class MyMapper implements MapFunction<String, String>,
> EventTimeFunction {
> private long currentEventTime = Long.MIN_VALUE;
> public String map(String value) {
> return value + " @ " + currentEventTime;
> }
> public void onWatermark(Watermark watermark) {
> currentEventTime = watermark.getTimestamp();
> }
> }
> {code}
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