text: #!/usr/bin/env python
  
  '''
  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 sys
  import logging
  import threading
  import socket
  from ambari_commons import subprocess32
  
  logger = logging.getLogger(__name__)
  FUSER_CMD = "fuser {0}/tcp 2>/dev/null | awk '{1}'"
  PSPF_CMD = "ps -fp {0}"
  PORT_IN_USE_MESSAGE = "Could not open port {0} because port already used by another process:\n{1}"
  
  class PingPortListener(threading.Thread):
  
    def __init__(self, config):
      threading.Thread.__init__(self)
      self.daemon = True
      self.running = True
      self.config = config
      self.host = '0.0.0.0'
      self.port = int(self.config.get('agent','ping_port'))
      if not self.port == None and not self.port == 0:
        (stdoutdata, stderrdata) = self.run_os_command_in_shell(FUSER_CMD.format(str(self.port), "{print $1}"))
        if stdoutdata.strip() and stdoutdata.strip().isdigit():
          (stdoutdata, stderrdata) = self.run_os_command_in_shell(PSPF_CMD.format(stdoutdata.strip()))
          raise Exception(PORT_IN_USE_MESSAGE.format(str(self.port), stdoutdata))      
      self.socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
      self.socket.bind((self.host, self.port))
      self.socket.listen(1)
      config.set('agent','current_ping_port',str(self.socket.getsockname()[1]))
      logger.info("Ping port listener started on port: " + str(self.socket.getsockname()[1]))
  
  
    def run_os_command_in_shell(self, command):
      process = subprocess32.Popen(command, stdout=subprocess32.PIPE,
                stdin=subprocess32.PIPE,
                stderr=subprocess32.PIPE,
                shell=True)
      return process.communicate()
  
    def __del__(self):
      logger.info("Ping port listener killed")
  
  
    def run(self):
      while  self.running:
        try:
          conn, addr = self.socket.accept()
          conn.send("OK")
          conn.close()
        except Exception as ex:
          logger.error("Failed in Ping port listener because of:" + str(ex));
          sys.exit(1)
    pass
  