scala - SparkContext 和 StreamingContext 可以共存于同一个程序中吗？

Question

我正在尝试设置一个 Sparkstreaming 代码，它从 Kafka 服务器读取行，但使用另一个本地文件中编写的规则处理它。我正在为流数据创建streamingContext，为其他应用所有其他spark 功能创建sparkContext - 如字符串操作、读取本地文件等

val sparkConf = new SparkConf().setMaster("local[*]").setAppName("ReadLine")
val ssc = new StreamingContext(sparkConf, Seconds(15))
ssc.checkpoint("checkpoint")

    val topicMap = topics.split(",").map((_, numThreads.toInt)).toMap
    val lines = KafkaUtils.createStream(ssc, zkQuorum, group, topicMap).map(_._2)
    val sentence = lines.toString

    val conf = new SparkConf().setAppName("Bi Gram").setMaster("local[2]")
    val sc = new SparkContext(conf)
    val stringRDD = sc.parallelize(Array(sentence))

但这会引发以下错误

Exception in thread "main" org.apache.spark.SparkException: Only one SparkContext may be running in this JVM (see SPARK-2243). To ignore this error, set spark.driver.allowMultipleContexts = true. The currently running SparkContext was created at:
org.apache.spark.SparkContext.<init>(SparkContext.scala:82)
org.apache.spark.streaming.StreamingContext$.createNewSparkContext(StreamingContext.scala:874)
org.apache.spark.streaming.StreamingContext.<init>(StreamingContext.scala:81)

Answer 1

一个申请只能有一个 SparkContext . StreamingContext创建于 SparkContext .只需要使用 SparkContext 创建 ssc StreamingContext

val sc = new SparkContext(conf)
val ssc = new StreamingContext(sc, Seconds(15))

如果使用以下构造函数。

StreamingContext(conf: SparkConf, batchDuration: Duration)

它在内部创建了另一个 SparkContext

this(StreamingContext.createNewSparkContext(conf), null, batchDuration)

SparkContext可以从StreamingContext获取经过

ssc.sparkContext