title: No File writen down to HDFS in flink
body: <p>I'm trying to consume kafka by flink and save the result to hdfs but no file was produces all the time.. and no error message raise up.. </p>
  
  <p>btw, it's ok to save to local file but when I change the path to hdfs, I got nothing.</p>
  
  <pre><code>object kafka2Hdfs {
  
     private val ZOOKEEPER_HOST = "ip1:2181,ip2:2181,ip3:2181"
     private val KAFKA_BROKER = "ip1:9092,ip2:9092,ip3:9092"
  
    private val TRANSACTION_GROUP = "transaction"
    val topic = "tgt3"
  
    def main(args : Array[String]){
      val env = StreamExecutionEnvironment.getExecutionEnvironment
      env.setStreamTimeCharacteristic(TimeCharacteristic.EventTime)
      env.enableCheckpointing(1000L)
      env.getCheckpointConfig.setCheckpointingMode(CheckpointingMode.EXACTLY_ONCE)
  
      // configure Kafka consumer
      val kafkaProps = new Properties()
      .... //topic infos
      kafkaProps.setProperty("fs.default-scheme", "hdfs://ip:8020")
  
      val consumer = new FlinkKafkaConsumer010[String](topic, new SimpleStringSchema(), kafkaProps)
      val source = env.addSource(consumer)
  
      val path = new Path("/user/jay/data")
  
      // sink
      val rollingPolicy : RollingPolicy[String,String] = DefaultRollingPolicy.create()
        .withRolloverInterval(15000)
        .build()
  
      val sink: StreamingFileSink[String] = StreamingFileSink
        .forRowFormat(path, new SimpleStringEncoder[String]("UTF-8"))
        .withRollingPolicy(rollingPolicy)
        .build()
  
      source.addSink(sink)
  
      env.execute("test")
    }
  }
  </code></pre>
  
  <p>I'm very confused..</p>