极客时间《消息队列高手课》案例篇《30. 流计算与消息（二）：在流计算中使用Kafka链接计算任务》示例源代码。
运行示例之前需要先安装：
- JDK 1.8
- Scala 2.12
- Maven 3.3.9
$java -version
java version "1.8.0_202"
Java(TM) SE Runtime Environment (build 1.8.0_202-b08)
Java HotSpot(TM) 64-Bit Server VM (build 25.202-b08, mixed mode)
$scala -version
Scala code runner version 2.12.4 -- Copyright 2002-2017, LAMP/EPFL and Lightbend, Inc.
$mvn -version
Apache Maven 3.3.9 (bb52d8502b132ec0a5a3f4c09453c07478323dc5; 2015-11-11T00:41:47+08:00)$git clone [email protected]:liyue2008/kafka-flink-exactlyonce-example.git
$cd kafka-flink-exactlyonce-example
$mvn package去Flink官网下载页面，下载Apache Flink 1.9.0 for Scala 2.12，文件名为：flink-1.9.0-bin-scala_2.12.tgz。
解压到目录：flink-1.9.0
修改flink-1.9.0/conf/flink-conf.yaml，将槽数改为8：
# The number of task slots that each TaskManager offers. Each slot runs one parallel pipeline.
taskmanager.numberOfTaskSlots: 8启动Flink集群：
$ bin/start-cluster.sh
Starting cluster.
Starting standalonesession daemon on host localhost.
Starting taskexecutor daemon on host localhost.去Kafka官网下载页面下载kafka_2.12-2.3.0.tgz。
解压到目录：kafka_2.12-2.3.0
修改kafka_2.12-2.3.0/config/server.properties，设置事务超时：
max.transaction.timeout.ms=90000启动ZooKeeper和Kafka：
$cd kafka_2.12-2.3.0
$bin/zookeeper-server-start.sh config/zookeeper.properties
$bin/kafka-server-start.sh config/server.properties创建主题
$bin/kafka-topics.sh --create --bootstrap-server localhost:9092 --replication-factor 1 --partitions 1 --topic ip_count_source
$bin/kafka-topics.sh --create --bootstrap-server localhost:9092 --replication-factor 1 --partitions 1 --topic ip_count_sink首先需要启动模拟日志的Kafka Producer，作为数据源
$cd kafka-flink-exactlyonce-example
$java -jar nginx-log-producer/target/nginx-log-producer-1.0-SNAPSHOT-jar-with-dependencies.jar$flink-1.9.0/bin/flink run ip-count/target/ip-count-1.0-SNAPSHOT.jar
Starting execution of program注意设置isolation.level=read_committed，否则会消费到未提交的事务消息。
$cd kafka_2.12-2.3.0
$bin/kafka-console-consumer.sh --bootstrap-server localhost:9092 --property isolation.level=read_committed --topic ip_count_sink
2019-09-15_16:23:35 192.168.1.1 5
2019-09-15_16:23:35 192.168.1.4 5
2019-09-15_16:23:35 192.168.1.3 5
2019-09-15_16:23:35 192.168.1.2 5
2019-09-15_16:23:40 192.168.1.2 5
2019-09-15_16:23:40 192.168.1.1 5
2019-09-15_16:23:40 192.168.1.4 5
2019-09-15_16:23:40 192.168.1.3 5
2019-09-15_16:23:45 192.168.1.2 5
2019-09-15_16:23:45 192.168.1.3 5
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