text: #
  # Licensed to the Apache Software Foundation (ASF) under one or more
  # contributor license agreements.  See the NOTICE file distributed with
  # this work for additional information regarding copyright ownership.
  # The ASF licenses this file to You under the Apache License, Version 2.0
  # (the "License"); you may not use this file except in compliance with
  # the License.  You may obtain a copy of the License at
  #
  #    http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  #
  
  import os
  import sys
  import signal
  import shlex
  import platform
  from subprocess import Popen, PIPE
  from threading import Thread
  from py4j.java_gateway import java_import, JavaGateway, GatewayClient
  
  
  def launch_gateway():
      SPARK_HOME = os.environ["SPARK_HOME"]
  
      gateway_port = -1
      if "PYSPARK_GATEWAY_PORT" in os.environ:
          gateway_port = int(os.environ["PYSPARK_GATEWAY_PORT"])
      else:
          # Launch the Py4j gateway using Spark's run command so that we pick up the
          # proper classpath and settings from spark-env.sh
          on_windows = platform.system() == "Windows"
          script = "./bin/spark-submit.cmd" if on_windows else "./bin/spark-submit"
          submit_args = os.environ.get("PYSPARK_SUBMIT_ARGS")
          submit_args = submit_args if submit_args is not None else ""
          submit_args = shlex.split(submit_args)
          command = [os.path.join(SPARK_HOME, script), "pyspark-shell"] + submit_args
          if not on_windows:
              # Don't send ctrl-c / SIGINT to the Java gateway:
              def preexec_func():
                  signal.signal(signal.SIGINT, signal.SIG_IGN)
              proc = Popen(command, stdout=PIPE, stdin=PIPE, preexec_fn=preexec_func)
          else:
              # preexec_fn not supported on Windows
              proc = Popen(command, stdout=PIPE, stdin=PIPE)
  
          try:
              # Determine which ephemeral port the server started on:
              gateway_port = proc.stdout.readline()
              gateway_port = int(gateway_port)
          except ValueError:
              (stdout, _) = proc.communicate()
              exit_code = proc.poll()
              error_msg = "Launching GatewayServer failed"
              error_msg += " with exit code %d! " % exit_code if exit_code else "! "
              error_msg += "(Warning: unexpected output detected.)\n\n"
              error_msg += gateway_port + stdout
              raise Exception(error_msg)
  
          # Create a thread to echo output from the GatewayServer, which is required
          # for Java log output to show up:
          class EchoOutputThread(Thread):
              def __init__(self, stream):
                  Thread.__init__(self)
                  self.daemon = True
                  self.stream = stream
  
              def run(self):
                  while True:
                      line = self.stream.readline()
                      sys.stderr.write(line)
          EchoOutputThread(proc.stdout).start()
  
      # Connect to the gateway
      gateway = JavaGateway(GatewayClient(port=gateway_port), auto_convert=False)
  
      # Import the classes used by PySpark
      java_import(gateway.jvm, "org.apache.spark.SparkConf")
      java_import(gateway.jvm, "org.apache.spark.api.java.*")
      java_import(gateway.jvm, "org.apache.spark.api.python.*")
      java_import(gateway.jvm, "org.apache.spark.mllib.api.python.*")
      java_import(gateway.jvm, "org.apache.spark.sql.SQLContext")
      java_import(gateway.jvm, "org.apache.spark.sql.hive.HiveContext")
      java_import(gateway.jvm, "org.apache.spark.sql.hive.LocalHiveContext")
      java_import(gateway.jvm, "org.apache.spark.sql.hive.TestHiveContext")
      java_import(gateway.jvm, "scala.Tuple2")
  
      return gateway
  