Apache Flink 零基础入门（十三）Flink 计数器_flink全局计数器

需求：当一个文本文件进入时，有可能会有一些格式乱码的错误行，如何统计哪些错误行？如何提取错误行

  def main(args: Array[String]): Unit = {
    val env  = ExecutionEnvironment.getExecutionEnvironment
    val data = env.fromElements("hadoop","spark","pyspark", "storm")
    data.map(new RichMapFunction[String, Long] {
      var counter = 0l
      override def map(value: String): Long = {
        counter = counter + 1
        println("counter:"+counter)
        counter
      }
    }).setParallelism(2).print()
 
  }

使用这种方式，设置并行度之后，无法正确统计。

正确的方式是通过定义Accumulator来进行计数操作。scala实现方式如下：

val info = data.map(new RichMapFunction[String, String] {
      // step1：定义计数器
      val counter  = new LongCounter()
      override def open(parameters: Configuration): Unit = {
        // step2: 注册计数器
        getRuntimeContext.addAccumulator("ele-counts-scala", counter)
      }
      override def map(in: String): String = {
        counter.add(1)
        in
      }
    })
    info.writeAsText("E:/test3", WriteMode.OVERWRITE).setParallelism(4)
    val jobResult=env.execute("CounterApp")
    // step3: 获取计数器
    val num =jobResult.getAccumulatorResult[Long]("ele-counts-scala")
    println("num:" + num )

Java

public class JavaCounterApp {
    public static void main(String[] args) throws Exception {
        ExecutionEnvironment executionEnvironment = ExecutionEnvironment.getExecutionEnvironment();
        DataSource<String> data = executionEnvironment.fromElements("hadoop", "spark", "pyspark", "storm");
        DataSet dataSet = data.map(new RichMapFunction<String, String>() {
            LongCounter counter = new LongCounter();
 
            @Override
            public void open(Configuration parameters) throws Exception {
                getRuntimeContext().addAccumulator("ele-counts-java",counter);
            }
 
            @Override
            public String map(String value) throws Exception {
                counter.add(1);
                return value;
            }
        });
        dataSet.writeAsText("E:/test4", FileSystem.WriteMode.OVERWRITE).setParallelism(3);
        JobExecutionResult javaCounterApp = executionEnvironment.execute("JavaCounterApp");
        long num = javaCounterApp.getAccumulatorResult("ele-counts-java");
        System.out.println("num:" + num);
    }
}