docstr: Verify that BarrierTaskContext.barrier() performs global sync among all barrier tasks
  within a stage.
docstr_tok: ["Verify","that","BarrierTaskContext.barrier","(",")","performs","global","sync","among","all","barrier","tasks","within","a","stage","."]
code: def test_barrier(self):
      """
      Verify that BarrierTaskContext.barrier() performs global sync among all barrier tasks
      within a stage.
      """
      rdd = self.sc.parallelize(range(10), 4)
  
      def f(iterator):
          yield sum(iterator)
  
      def context_barrier(x):
          tc = BarrierTaskContext.get()
          time.sleep(random.randint(1, 5) * 2)
          tc.barrier()
          return time.time()
  
      times = (
          rdd.barrier().mapPartitions(f).map(context_barrier).collect()
      )
      self.assertTrue(max(times) - min(times) < 2)
  
imports: import os
  import random
  import stat
  import sys
  import tempfile
  import time
  import unittest
  from pyspark import SparkConf, SparkContext, TaskContext, BarrierTaskContext
  from pyspark.testing.utils import PySparkTestCase, SPARK_HOME, eventually
label_desc: Use image node_id 8 for calling the TaskContextTests obj's underlying member method code with example usage: obj.test_barrier() and returns: time