Github user medcv commented on a diff in the pull request:
https://github.com/apache/flink/pull/6136#discussion_r193934744
--- Diff:
flink-examples/flink-examples-cep/src/main/java/org/apache/flink/cep/examples/java/monitoring/TemperatureMonitoring.java
---
@@ -0,0 +1,147 @@
+/*
+ * 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.cep.examples.java.monitoring;
+
+import org.apache.flink.cep.CEP;
+import org.apache.flink.cep.PatternFlatSelectFunction;
+import org.apache.flink.cep.PatternSelectFunction;
+import org.apache.flink.cep.PatternStream;
+import
org.apache.flink.cep.examples.java.monitoring.events.MonitoringEvent;
+import
org.apache.flink.cep.examples.java.monitoring.events.TemperatureAlert;
+import
org.apache.flink.cep.examples.java.monitoring.events.TemperatureEvent;
+import
org.apache.flink.cep.examples.java.monitoring.events.TemperatureWarning;
+import
org.apache.flink.cep.examples.java.monitoring.sources.MonitoringEventSource;
+import org.apache.flink.cep.pattern.Pattern;
+import org.apache.flink.cep.pattern.conditions.SimpleCondition;
+import org.apache.flink.streaming.api.TimeCharacteristic;
+import org.apache.flink.streaming.api.datastream.DataStream;
+import
org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
+import org.apache.flink.streaming.api.functions.IngestionTimeExtractor;
+import org.apache.flink.streaming.api.windowing.time.Time;
+import org.apache.flink.util.Collector;
+
+import java.util.List;
+import java.util.Map;
+
+/**
+ * CEP example monitoring program.
+ * This example program generates a stream of monitoring events which are
analyzed using
+ * Flink's CEP library. The input event stream consists of temperature and
power events
+ * from a set of racks. The goal is to detect when a rack is about to
overheat.
+ * In order to do that, we create a CEP pattern which generates a
TemperatureWarning
+ * whenever it sees two consecutive temperature events in a given time
interval whose temperatures
+ * are higher than a given threshold value. A warning itself is not
critical but if we see
+ * two warning for the same rack whose temperatures are rising, we want to
generate an alert.
+ * This is achieved by defining another CEP pattern which analyzes the
stream of generated
+ * temperature warnings.
+ */
+public class TemperatureMonitoring {
+
+ private static final double TEMPERATURE_THRESHOLD = 100;
+
+ public static void main(String[] args) throws Exception {
+ System.out.println("Executing temperature monitoring Java
example.");
+ StreamExecutionEnvironment env =
StreamExecutionEnvironment.getExecutionEnvironment();
+
+ // Use ingestion time => TimeCharacteristic == EventTime +
IngestionTimeExtractor
+ env.setStreamTimeCharacteristic(TimeCharacteristic.EventTime);
+
+ // Input stream of monitoring events
+ DataStream<MonitoringEvent> inputEventStream =
env.addSource(new MonitoringEventSource())
+ .assignTimestampsAndWatermarks(new
IngestionTimeExtractor<>());
+
+ // Warning pattern: Two consecutive temperature events whose
temperature is higher
+ // than the given threshold appearing within a time interval of
10 seconds
+ Pattern<MonitoringEvent, ?> warningPattern = Pattern
+ .<MonitoringEvent>begin("first")
+ .subtype(TemperatureEvent.class)
+ .where(new SimpleCondition<TemperatureEvent>() {
+ @Override
+ public boolean filter(TemperatureEvent
event) throws Exception {
+ return event.getTemperature() >
TEMPERATURE_THRESHOLD;
+ }
+ })
+ .next("second")
+ .subtype(TemperatureEvent.class)
+ .where(new SimpleCondition<TemperatureEvent>() {
+ @Override
+ public boolean filter(TemperatureEvent
event) throws Exception {
+ return event.getTemperature() >
TEMPERATURE_THRESHOLD;
+ }
+ })
+ .within(Time.seconds(10));
+
+ // Create a pattern stream from our warning pattern
+ PatternStream<MonitoringEvent> tempPatternStream = CEP.pattern(
+ inputEventStream.keyBy("rackID"),
+ warningPattern);
+
+ // Generate temperature warnings for each matched warning
pattern
+ DataStream<TemperatureWarning> warnings =
tempPatternStream.select(
+ new PatternSelectFunction<MonitoringEvent,
TemperatureWarning>() {
+ @Override
+ public TemperatureWarning select(
+ Map<String,
List<MonitoringEvent>> pattern) throws Exception {
+ TemperatureEvent first =
(TemperatureEvent) pattern.get("first").get(0);
+ TemperatureEvent second =
(TemperatureEvent) pattern.get("second").get(0);
+ return new TemperatureWarning(
+ first.getRackID(),
+ (first.getTemperature() +
second.getTemperature()) / 2
+ );
+ }
+ }
+ );
+
+ // Alert pattern: Two consecutive temperature warnings
+ // appearing within a time interval of 20 seconds
+ Pattern<TemperatureWarning, ?> alertPattern = Pattern
+ .<TemperatureWarning>begin("first")
+ .next("second")
+ .within(Time.seconds(20));
+
+ // Create a pattern stream from our alert pattern
+ PatternStream<TemperatureWarning> alertPatternStream =
CEP.pattern(
+ warnings.keyBy("rackID"),
+ alertPattern);
+
+ // Generate a temperature alert iff the second temperature
warning's average temperature
--- End diff --
type `iff`
---
