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# Licensed to the Apache Software Foundation (ASF) under one
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# 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.
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import logging
import sys
import os
import traceback
import threading
import Queue

from thrift.Thrift import TProcessor
from thrift.transport import TTransport
from thrift.protocol import TBinaryProtocol

class TServer:

  """Base interface for a server, which must have a serve method."""

  """ 3 constructors for all servers:
  1) (processor, serverTransport)
  2) (processor, serverTransport, transportFactory, protocolFactory)
  3) (processor, serverTransport,
      inputTransportFactory, outputTransportFactory,
      inputProtocolFactory, outputProtocolFactory)"""
  def __init__(self, *args):
    if (len(args) == 2):
      self.__initArgs__(args[0], args[1],
                        TTransport.TTransportFactoryBase(),
                        TTransport.TTransportFactoryBase(),
                        TBinaryProtocol.TBinaryProtocolFactory(),
                        TBinaryProtocol.TBinaryProtocolFactory())
    elif (len(args) == 4):
      self.__initArgs__(args[0], args[1], args[2], args[2], args[3], args[3])
    elif (len(args) == 6):
      self.__initArgs__(args[0], args[1], args[2], args[3], args[4], args[5])

  def __initArgs__(self, processor, serverTransport,
                   inputTransportFactory, outputTransportFactory,
                   inputProtocolFactory, outputProtocolFactory):
    self.processor = processor
    self.serverTransport = serverTransport
    self.inputTransportFactory = inputTransportFactory
    self.outputTransportFactory = outputTransportFactory
    self.inputProtocolFactory = inputProtocolFactory
    self.outputProtocolFactory = outputProtocolFactory

  def serve(self):
    pass

class TSimpleServer(TServer):

  """Simple single-threaded server that just pumps around one transport."""

  def __init__(self, *args):
    TServer.__init__(self, *args)

  def serve(self):
    self.serverTransport.listen()
    while True:
      client = self.serverTransport.accept()
      itrans = self.inputTransportFactory.getTransport(client)
      otrans = self.outputTransportFactory.getTransport(client)
      iprot = self.inputProtocolFactory.getProtocol(itrans)
      oprot = self.outputProtocolFactory.getProtocol(otrans)
      try:
        while True:
          self.processor.process(iprot, oprot)
      except TTransport.TTransportException, tx:
        pass
      except Exception, x:
        logging.exception(x)

      itrans.close()
      otrans.close()

class TThreadedServer(TServer):

  """Threaded server that spawns a new thread per each connection."""

  def __init__(self, *args):
    TServer.__init__(self, *args)

  def serve(self):
    self.serverTransport.listen()
    while True:
      try:
        client = self.serverTransport.accept()
        t = threading.Thread(target = self.handle, args=(client,))
        t.start()
      except KeyboardInterrupt:
        raise
      except Exception, x:
        logging.exception(x)

  def handle(self, client):
    itrans = self.inputTransportFactory.getTransport(client)
    otrans = self.outputTransportFactory.getTransport(client)
    iprot = self.inputProtocolFactory.getProtocol(itrans)
    oprot = self.outputProtocolFactory.getProtocol(otrans)
    try:
      while True:
        self.processor.process(iprot, oprot)
    except TTransport.TTransportException, tx:
      pass
    except Exception, x:
      logging.exception(x)

    itrans.close()
    otrans.close()

class TThreadPoolServer(TServer):

  """Server with a fixed size pool of threads which service requests."""

  def __init__(self, *args):
    TServer.__init__(self, *args)
    self.clients = Queue.Queue()
    self.threads = 10

  def setNumThreads(self, num):
    """Set the number of worker threads that should be created"""
    self.threads = num

  def serveThread(self):
    """Loop around getting clients from the shared queue and process them."""
    while True:
      try:
        client = self.clients.get()
        self.serveClient(client)
      except Exception, x:
        logging.exception(x)

  def serveClient(self, client):
    """Process input/output from a client for as long as possible"""
    itrans = self.inputTransportFactory.getTransport(client)
    otrans = self.outputTransportFactory.getTransport(client)
    iprot = self.inputProtocolFactory.getProtocol(itrans)
    oprot = self.outputProtocolFactory.getProtocol(otrans)
    try:
      while True:
        self.processor.process(iprot, oprot)
    except TTransport.TTransportException, tx:
      pass
    except Exception, x:
      logging.exception(x)

    itrans.close()
    otrans.close()

  def serve(self):
    """Start a fixed number of worker threads and put client into a queue"""
    for i in range(self.threads):
      try:
        t = threading.Thread(target = self.serveThread)
        t.start()
      except Exception, x:
        logging.exception(x)

    # Pump the socket for clients
    self.serverTransport.listen()
    while True:
      try:
        client = self.serverTransport.accept()
        self.clients.put(client)
      except Exception, x:
        logging.exception(x)


class TForkingServer(TServer):

  """A Thrift server that forks a new process for each request"""
  """
  This is more scalable than the threaded server as it does not cause
  GIL contention.

  Note that this has different semantics from the threading server.
  Specifically, updates to shared variables will no longer be shared.
  It will also not work on windows.

  This code is heavily inspired by SocketServer.ForkingMixIn in the
  Python stdlib.
  """

  def __init__(self, *args):
    TServer.__init__(self, *args)
    self.children = []

  def serve(self):
    def try_close(file):
      try:
        file.close()
      except IOError, e:
        logging.warning(e, exc_info=True)


    self.serverTransport.listen()
    while True:
      client = self.serverTransport.accept()
      try:
        pid = os.fork()

        if pid: # parent
          # add before collect, otherwise you race w/ waitpid
          self.children.append(pid)
          self.collect_children()

          # Parent must close socket or the connection may not get
          # closed promptly
          itrans = self.inputTransportFactory.getTransport(client)
          otrans = self.outputTransportFactory.getTransport(client)
          try_close(itrans)
          try_close(otrans)
        else:
          itrans = self.inputTransportFactory.getTransport(client)
          otrans = self.outputTransportFactory.getTransport(client)

          iprot = self.inputProtocolFactory.getProtocol(itrans)
          oprot = self.outputProtocolFactory.getProtocol(otrans)

          ecode = 0
          try:
            try:
              while True:
                self.processor.process(iprot, oprot)
            except TTransport.TTransportException, tx:
              pass
            except Exception, e:
              logging.exception(e)
              ecode = 1
          finally:
            try_close(itrans)
            try_close(otrans)

          os._exit(ecode)

      except TTransport.TTransportException, tx:
        pass
      except Exception, x:
        logging.exception(x)


  def collect_children(self):
    while self.children:
      try:
        pid, status = os.waitpid(0, os.WNOHANG)
      except os.error:
        pid = None

      if pid:
        self.children.remove(pid)
      else:
        break


