[SPARK-17552] Doubt about the double Synchronized in Object SparkSession.getOrCreate()

• Type: Question
• Status: Resolved
• Priority: Trivial
• Resolution: Invalid
• Affects Version/s: 2.0.0
• Component/s: Spark Core, SQL
• Labels: features
• Flags: Important
• Assignee: Unassigned
• Reporter: Jianfei Wang
• Created: 15/Sep/16 07:45
• Updated: 15/Sep/16 07:57
• Resolved: 15/Sep/16 07:48

Description

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!

 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
    }