在同一个JVM中检测到多个SparkContext

Question

根据我的最后一个问题，我必须为我的唯一JVM定义Multiple SparkContext。

我以另一种方式（使用Java）做到了：

SparkConf conf = new SparkConf();
conf.setAppName("Spark MultipleContest Test");
conf.set("spark.driver.allowMultipleContexts", "true");
conf.setMaster("local");

之后，我创建下一个源代码：

SparkContext sc = new SparkContext(conf);
SQLContext sqlContext = new org.apache.spark.sql.SQLContext(sc);

然后在代码中：

JavaSparkContext ctx = new JavaSparkContext(conf);
JavaRDD<Row> testRDD = ctx.parallelize(AllList);

执行代码后，我收到下一条错误消息：

16/01/19 15:21:08 WARN SparkContext: Multiple running SparkContexts detected in the same JVM!
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:81)
test.MLlib.BinarryClassification.main(BinaryClassification.java:41)
    at org.apache.spark.SparkContext$$anonfun$assertNoOtherContextIsRunning$1.apply(SparkContext.scala:2083)
    at org.apache.spark.SparkContext$$anonfun$assertNoOtherContextIsRunning$1.apply(SparkContext.scala:2065)
    at scala.Option.foreach(Option.scala:236)
    at org.apache.spark.SparkContext$.assertNoOtherContextIsRunning(SparkContext.scala:2065)
    at org.apache.spark.SparkContext$.setActiveContext(SparkContext.scala:2151)
    at org.apache.spark.SparkContext.<init>(SparkContext.scala:2023)
    at org.apache.spark.api.java.JavaSparkContext.<init>(JavaSparkContext.scala:61)
    at test.MLlib.BinarryClassification.main(BinaryClassification.java:105)

数字41和105是行，其中两个对象都用Java代码定义。我的问题是，如果我已经使用set-method
，是否可以在同一JVM上执行多个SparkContext以及如何执行？

Answer 1

您确定需要将JavaSparkContext作为单独的上下文吗？您提到的上一个问题没有这么说。如果您已经拥有一个Spark
Context，则可以从中创建一个新的JavaSparkContext，而不用创建单独的上下文：

SparkConf conf = new SparkConf();
conf.setAppName("Spark MultipleContest Test");
conf.set("spark.driver.allowMultipleContexts", "true");
conf.setMaster("local");

SparkContext sc = new SparkContext(conf);
SQLContext sqlContext = new org.apache.spark.sql.SQLContext(sc);

//Create a Java Context which is the same as the html" target="_blank">scala one under the hood
JavaSparkContext.fromSparkContext(sc)