6-计数器

计数器：

基于flink开发计数器的三步：

step1：定义计数器

LongCounter counter = new LongCounter();

step2：注册计数器：

getRuntimeContext().addAccumulator("ele-counts-java", counter);

step3：获取计数器

long num = jobResult.getAccumulatorResult("ele-counts-java");

示例：

public static void main(String[] args) throws Exception {

    ExecutionEnvironment env = ExecutionEnvironment.getExecutionEnvironment();

    DataSource<String> data = env.fromElements("hadoop","spark","flink","pyspark","storm");

    DataSet<String> info = data.map(new RichMapFunction<String, String>() {

        //step1：定义计数器

        LongCounter counter = new LongCounter();

        @Override

        public void open(Configuration parameters) throws Exception {

            super.open(parameters);

            //step2:注册计数器

            getRuntimeContext().addAccumulator("ele-counts-java", counter);

        }

        public String map(String value) throws Exception {

            counter.add(1);

            return value;

        }

    });

    String filePath = "D:\\yly\\BaiduNetdiskDownload\\最全最新flink教程\\000.代码+环境\\00.flink-train-master\\flink-train\\data\\04\\inputs1\\";

    info.writeAsText(filePath, FileSystem.WriteMode.OVERWRITE).setParallelism(2);

    JobExecutionResult jobResult = env.execute("CounterApp");

    // step3: 获取计数器

    long num = jobResult.getAccumulatorResult("ele-counts-java");

    System.out.println("num = [" + num + "]");

}