[GitHub] [flink] sjwiesman commented on a change in pull request #9192: [FLINK-12749] [docs] [examples] Initial Version of Flink Cluster Playground

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sjwiesman commented on a change in pull request #9192: [FLINK-12749] [docs] [examples] Initial Version of Flink Cluster Playground
URL: https://github.com/apache/flink/pull/9192#discussion_r305946262
 
 

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 File path: flink-examples/flink-examples-streaming/src/main/java/org/apache/flink/streaming/examples/windowing/clickeventcount/functions/ClickEventStatisticsCollector.java
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 @@ -0,0 +1,45 @@
+/*
+ * 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.examples.windowing.clickeventcount.functions;
+
+import org.apache.flink.streaming.api.functions.windowing.ProcessWindowFunction;
+import org.apache.flink.streaming.api.windowing.windows.TimeWindow;
+import org.apache.flink.streaming.examples.windowing.clickeventcount.records.ClickEvent;
+import org.apache.flink.streaming.examples.windowing.clickeventcount.records.ClickEventStatistics;
+import org.apache.flink.util.Collector;
+
+/**
+ * A simple {@link ProcessWindowFunction}, which wraps a count of {@link ClickEvent}s into an
+ * instance of {@link ClickEventStatistics}.
+ *
+ **/
+public class ClickEventStatisticsCollector
+		extends ProcessWindowFunction<Long, ClickEventStatistics, String, TimeWindow> {
+
+	@Override
+	public void process(
+			final String page,
+			final Context context,
+			final Iterable<Long> elements,
+			final Collector<ClickEventStatistics> out) throws Exception {
+
+		Long count = elements.iterator().next();
+
+		out.collect(new ClickEventStatistics(context.window().getStart(), context.window().getEnd(), page, count));
 
 Review comment:
   I originally started to write a comment that you should have `CountingAggregator#getResult` return a `ClickEventStatistics` object but now I see you are getting the start and stop times of the window. Maybe add a comment for new users who make the same mistake I did :) 

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