Jianfei Wang created SPARK-17552:
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             Summary: Doubt about the double Synchronized in Object 
SparkSession.getOrCreate()
                 Key: SPARK-17552
                 URL: https://issues.apache.org/jira/browse/SPARK-17552
             Project: Spark
          Issue Type: Question
          Components: Spark Core, SQL
    Affects Versions: 2.0.0
            Reporter: Jianfei Wang
            Priority: Trivial


Because the getOrCreate() is a method of object SparkSession,  only one thread 
can get into the first synchronized block at the same time, so I think the 
second synchronzied is unnecessary, of course maybe there are some other 
reasons, please discuss here,thank you! 
{code}
 def getOrCreate(): SparkSession = synchronized {
      // Get the session from current thread's active session.
      var session = activeThreadSession.get()
      if ((session ne null) && !session.sparkContext.isStopped) {
        options.foreach { case (k, v) => session.conf.set(k, v) }
        if (options.nonEmpty) {
          logWarning("Use an existing SparkSession, some configuration may not 
take effect.")
        }
        return session
      }

      // Global synchronization so we will only set the default session once.
      SparkSession.synchronized {
       // some code here
     }
      

      return session
    }
{code}



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