Flink入门学习[0]

依赖环境

请确认以下环境已经正确安装

• Java 8.x
• Maven 3.0.4 (or higher)

验证java

$ java -version
java version "1.8.0_191"
Java(TM) SE Runtime Environment (build 1.8.0_191-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.191-b12, mixed mode)

验证maven

$ mvn -version
Apache Maven 3.6.0 (97c98ec64a1fdfee7767ce5ffb20918da4f719f3; 2018-10-25T02:41:47+08:00)
Maven home: /Users/dushixiang/Library/apache-maven-3.6.0
Java version: 1.8.0_191, vendor: Oracle Corporation, runtime: /Library/Java/JavaVirtualMachines/jdk1.8.0_191.jdk/Contents/Home/jre
Default locale: zh_CN, platform encoding: UTF-8
OS name: "mac os x", version: "10.14.1", arch: "x86_64", family: "mac"

下载安装Flink

Flink官网下载地址

可以看到这里有很多版本，由于这次只是本地开发，所以选择不带hadoop版本就可以，如果不打算使用scala开发的话，scala版本也无所谓。这里我下载了 flink-1.7.0-bin-scala_2.12.tgz，因为后面使用Java写Flink流处理的时候有点啰嗦，我会同时写java/scala两个版本的代码进行对比。

解压文件

tar -xvf flink-1.7.0-bin-scala_2.11.tgz 

本地模式启动

cd flink-1.7.0
bin/start-cluster.sh

验证是否成功启动

使用浏览器访问 localhost:8081 可以看到flink的UI界面

第一个Flink程序

使用shell命令创建一个quickstart程序

$ curl https://flink.apache.org/q/quickstart.sh | bash -s 1.7.0

使用maven命令创建一个quickstart程序

$ mvn archetype:generate                               \
      -DarchetypeGroupId=org.apache.flink              \
      -DarchetypeArtifactId=flink-quickstart-java      \
      -DarchetypeVersion=1.7.0

成功之后查看目录结构

$ tree quickstart/
quickstart/
├── pom.xml
└── src
    └── main
        ├── java
        │   └── org
        │       └── myorg
        │           └── quickstart
        │               ├── BatchJob.java
        │               └── StreamingJob.java
        └── resources
            └── log4j.properties

BatchJob.java 和StreamJob.java 都只是空壳，不必理会，修改pom中scala版本为2.12。

编写WordCount程序

package org.myorg.quickstart;

import org.apache.flink.api.common.functions.FlatMapFunction;
import org.apache.flink.api.java.tuple.Tuple2;
import org.apache.flink.streaming.api.datastream.DataStreamSource;
import org.apache.flink.streaming.api.datastream.SingleOutputStreamOperator;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
import org.apache.flink.util.Collector;

import java.util.stream.Stream;

public class WordCount {

    public static void main(String[] args) throws Exception {
        final StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();

        DataStreamSource text = env.fromElements(
                "Apache Flink is a framework and distributed processing engine for stateful computations over unbounded and bounded data streams. Flink has been designed to run in all common cluster environments, perform computations at in-memory speed and at any scale.",
                "Here, we explain important aspects of Flink’s architecture."
        );

        // 第一种 创建静态内部类Tokenizer类继承FlatMapFunction类并实现flatMap方法
        SingleOutputStreamOperator> counts = text
                .flatMap(new Tokenizer())
                .keyBy(0) // 使用元组的第一个元素当作key做分组
                .sum(1); // 使用元组的第二个元素统计该单词一共出现了多少次

        // 第二种 创建匿名内部类FlatMapFunction类并实现flatMap方法
        /*SingleOutputStreamOperator> counts = text.flatMap(new FlatMapFunction>() {
            @Override
            public void flatMap(String line, Collector> out) throws Exception {
                Stream.of(line.toLowerCase().split("\\W+"))
                    .filter(token -> token.length() > 0)
                    .forEach(token -> out.collect(new Tuple2<>(token, 1)));
            }
        })
                .keyBy(0)
                .sum(1);*/

        // 使用lambda表达式，此种方法会报错。原因是lambda方法不能提供足够的信息来进行自动类型提取，官方建议使用上面两种方法。
        /*SingleOutputStreamOperator> counts = text.flatMap((FlatMapFunction>) (line, out) -> {
            Stream.of(line.toLowerCase().split("\\W+"))
                    .filter(token -> token.length() > 0)
                    .forEach(token -> out.collect(new Tuple2<>(token, 1)));
        })
                .keyBy(0)
                .sum(1);*/


        counts.print();

        env.execute("第一个FLink WordCount程序");
    }

    public static final class Tokenizer implements FlatMapFunction> {

        @Override
        public void flatMap(String line, Collector> out) {
            Stream.of(line.toLowerCase().split("\\W+"))
                    .filter(token -> token.length() > 0)
                    .forEach(token -> out.collect(new Tuple2<>(token, 1)));
        }
    }
}

由于是本地模式，直接在IDE中编译运行即可。

接下来是scala版本的WordCount，首先在pom中添加依赖

        org.apache.flink
        flink-streaming-scala_${scala.binary.version}
        ${flink.version}

复制如下scala代码。

package org.myorg.quickstart.scala

import org.apache.flink.streaming.api.scala._

object WordCountScala {

  def main(args: Array[String]): Unit = {
    val env = StreamExecutionEnvironment.getExecutionEnvironment

    val text = env.fromElements(
      "Apache Flink is a framework and distributed processing engine for stateful computations over unbounded and bounded data streams. Flink has been designed to run in all common cluster environments, perform computations at in-memory speed and at any scale.",
      "Here, we explain important aspects of Flink’s architecture."
    )

    val counts = text
      .flatMap(_.toLowerCase.split("\\W+")) // 将多行输入分割之后压扁成一个列表
      .filter(_.nonEmpty) // 过滤掉空字符串
      .map((_, 1)) // 将字符转换为元组，字符作为元组的第一个参数，数字1作为元组的第二个参数
      .keyBy(0) // 使用元组的第一个元素当作key做分组
      .sum(1) // 使用元组的第二个元素统计该单词一共出现了多少次

    counts.print()

    env.execute("第一个FLink WordCount程序Scala版")
  }
}