如何在Zeppelin中将Flink var的内容写入屏幕？

Question

我尝试在Apache Zeppelin中运行以下简单命令.

%flink

var rabbit = env.fromElements(
"ARTHUR:  What, behind the rabbit?",
"TIM:  It is the rabbit!", 
"ARTHUR:  You silly sod!  You got us all worked up!",
"TIM:  Well, that's no ordinary rabbit.  That's the most foul, cruel, and bad-tempered rodent you ever set eyes on.",
"ROBIN:  You tit!  I soiled my armor I was so scared!", 
"TIM:  Look, that rabbit's got a vicious streak a mile wide, it's a killer!")

var counts = rabbit.flatMap { _.toLowerCase.split("\\W+")}.map{ (_,1)}.groupBy(0).sum(1) 

counts.print()

我尝试在笔记本中打印出结果.但不幸的是,我只得到以下输出.

rabbit: org.apache.flink.api.scala.DataSet[String] = org.apache.flink.api.scala.DataSet@37fdb65c
counts: org.apache.flink.api.scala.AggregateDataSet[(String, Int)] = org.apache.flink.api.scala.AggregateDataSet@1efc7158
res103: org.apache.flink.api.java.operators.DataSink[(String, Int)] = DataSink '<unnamed>' (Print to System.out)

如何在Zeppelin中将计数内容泄漏到笔记本中？

Answer 1

在Zeppelin中打印此类计算结果的方法是:

%flink
counts.collect().foreach(println(_))

//or one might prefer
//counts.collect foreach println 

输出:

(a,3)
(all,1)
(and,1)
(armor,1)
...

Answer 2

观察到的行为的原因在于 Apache Zeppelin 和 Apache Flink 之间的相互作用。Zeppelin 捕获Console. 然而，Flink 也会将输出打印到System.out，这正是您调用counts.print(). bzz 的解决方案之所以有效，是因为它使用 打印结果Console。

我打开了 JIRA 问题 [1] 并打开了拉取请求 [2] 来纠正此行为，以便您也可以使用counts.print().

• [1] https://issues.apache.org/jira/browse/ZEPPELIN-287
• [2] https://github.com/apache/incubator-zeppelin/pull/288