Flink自定义source（单并行度和多并行度）

1.Source简介

source是程序的数据源输入，你可以通过StreamExecutionEnvironment.addSource(sourceFunction)
来为你的程序添加一个source。

flink提供了大量的已经实现好的source方法，也可以自定义source：

1. 通过实现sourceFunction接口来自定义无并行度的source
2. 通过实现ParallelSourceFunction 接口or 继承RichParallelSourceFunction 来自定义有并行度的
   source

大多数情况下，我们使用自带的source即可。

2. Flink预定义的Source

flink提供了大量的已经实现好的source，常见的有：Flink source

• 基于文件的Source
• 基于Socket的Source
• 基于集合的Source
• 基于Kafka的Source

3. 自定义单并行度Source

除了flink本身提供的source之外，我们也可以自定义source。可以通过实现sourceFunction接口来自定义无并行度的source。

示例如下：

（1）自定义Source

import org.apache.flink.streaming.api.functions.source.SourceFunction;
//功能：每秒产生一条数据
public class MyNoParallelSource implements SourceFunction<Long> {
    private long number = 1L;
    private boolean isRunning = true;
    @Override
    public void run(SourceContext<Long> sct) throws Exception {
        while (isRunning){
            sct.collect(number);
            number++;
            //每秒生成一条数据
            Thread.sleep(1000);
        }
    }
    @Override
    public void cancel() {
        isRunning=false;
    }
}

（2）定义Consume，消费Source的数据，并打印输出

import org.apache.flink.api.common.functions.FilterFunction;
import org.apache.flink.api.common.functions.MapFunction;
import org.apache.flink.streaming.api.datastream.DataStream;
import org.apache.flink.streaming.api.datastream.DataStreamSource;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
//功能：打印输出偶数
public class MyNoParallelConsumer {
    public static void main(String[] args) throws Exception {
        //创建执行环境
        StreamExecutionEnvironment env= StreamExecutionEnvironment.getExecutionEnvironment();
        //默认并行度为1
        DataStreamSource<Long> numberStream = env.addSource(new MyNoParallelSource());
        DataStream<Long> dataStream = numberStream.map(new MapFunction<Long, Long>() {
            @Override
            public Long map(Long value) throws Exception {
                System.out.println("接受到了数据："+value);
                return value;
            }
        });
        DataStream<Long> filterDataStream = dataStream.filter(new FilterFunction<Long>() {
            @Override
            public boolean filter(Long value) throws Exception {
                return value % 2 == 0; //过滤偶数
            }
        });
        filterDataStream.print().setParallelism(1);
        env.execute();
    }
}

4. 自定义多并行度Source

通过实现ParallelSourceFunction 接口or 继承RichParallelSourceFunction 来自定义有并行度的
source。

（1）自定义多并行度Source

import org.apache.flink.streaming.api.functions.source.ParallelSourceFunction;
//功能：自定义支持并行度的数据源
public class MyParallelSource implements ParallelSourceFunction<Long> {
    private long number = 1L;
    private boolean isRunning = true;
    @Override
    public void run(SourceContext<Long> sct) throws Exception {
        while (isRunning){
            sct.collect(number);
            number++;
            //每秒生成一条数据
            Thread.sleep(1000);
        }
    }
    @Override
    public void cancel() {
        isRunning=false;
    }
}

（2）定义Consume，消费多并行度Source的数据，并打印输出

import org.apache.flink.api.common.functions.FilterFunction;
import org.apache.flink.api.common.functions.MapFunction;
import org.apache.flink.streaming.api.datastream.DataStream;
import org.apache.flink.streaming.api.datastream.DataStreamSource;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
//功能：消费多并行度Source的数据，并打印输出偶数
public class MyParallelConsumer {
    public static void main(String[] args) throws Exception {
        //创建执行环境
        StreamExecutionEnvironment env= StreamExecutionEnvironment.getExecutionEnvironment();
        //默认并行度为cpu core数，我这里为4
        DataStreamSource<Long> numberStream = env.addSource(new MyParallelSource());
        DataStream<Long> dataStream = numberStream.map(new MapFunction<Long, Long>() {
            @Override
            public Long map(Long value) throws Exception {
                System.out.println("接受到了数据："+value);
                return value;
            }
        });
        DataStream<Long> filterDataStream = dataStream.filter(new FilterFunction<Long>() {
            @Override
            public boolean filter(Long value) throws Exception {
                return value % 2 == 0;
            }
        });
        filterDataStream.print().setParallelism(1);
        env.execute();
    }
}

可以看到，如果不设置并行度，Source默认并行度为cpu core数，我这里是4。