Synnefo » snf-ganeti

#

#

# Copyright (C) 2006, 2007 Google Inc.

#

# This program is free software; you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation; either version 2 of the License, or

# (at your option) any later version.

#

# This program is distributed in the hope that it will be useful, but

# WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

# General Public License for more details.

#

# You should have received a copy of the GNU General Public License

# along with this program; if not, write to the Free Software

# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

# 02110-1301, USA.

"""Module for the unix socket protocol

This module implements the local unix socket protocl. You only need

this module and the opcodes module in the client program in order to

communicate with the master.

The module is also be used by the master daemon.

"""

import socket

import collections

import simplejson

import time

from ganeti import opcodes

KEY_REQUEST = 'request'

KEY_DATA = 'data'

REQ_SUBMIT = 'submit'

REQ_ABORT = 'abort'

REQ_QUERY = 'query'

DEF_CTMO = 10

DEF_RWTO = 60

class ProtocolError(Exception):

  """Denotes an error in the server communication"""

class ConnectionClosedError(ProtocolError):

  """Connection closed error"""

class TimeoutError(ProtocolError):

  """Operation timeout error"""

class EncodingError(ProtocolError):

  """Encoding failure on the sending side"""

class DecodingError(ProtocolError):

  """Decoding failure on the receiving side"""

def SerializeJob(job):

  """Convert a job description to a string format.

  """

  return simplejson.dumps(job.__getstate__())

def UnserializeJob(data):

  """Load a job from a string format"""

  try:

    new_data = simplejson.loads(data)

  except Exception, err:

    raise DecodingError("Error while unserializing: %s" % str(err))

  job = opcodes.Job()

  job.__setstate__(new_data)

  return job

class Transport:

  """Low-level transport class.

  This is used on the client side.

  This could be replace by any other class that provides the same

  semantics to the Client. This means:

    - can send messages and receive messages

    - safe for multithreading

  """

  def __init__(self, address, timeouts=None, eom=None):

    """Constructor for the Client class.

    Arguments:

      - address: a valid address the the used transport class

      - timeout: a list of timeouts, to be used on connect and read/write

      - eom: an identifier to be used as end-of-message which the

        upper-layer will guarantee that this identifier will not appear

        in any message

    There are two timeouts used since we might want to wait for a long

    time for a response, but the connect timeout should be lower.

    If not passed, we use a default of 10 and respectively 60 seconds.

    Note that on reading data, since the timeout applies to an

    invidual receive, it might be that the total duration is longer

    than timeout value passed (we make a hard limit at twice the read

    timeout).

    """

    self.address = address

    if timeouts is None:

      self._ctimeout, self._rwtimeout = DEF_CTMO, DEF_RWTO

    else:

      self._ctimeout, self._rwtimeout = timeouts

    self.socket = None

    self._buffer = ""

    self._msgs = collections.deque()

    if eom is None:

      self.eom = '\3'

    else:

      self.eom = eom

    try:

      self.socket = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)

      self.socket.settimeout(self._ctimeout)

      try:

        self.socket.connect(address)

      except socket.timeout, err:

        raise TimeoutError("Connection timed out: %s" % str(err))

      self.socket.settimeout(self._rwtimeout)

    except socket.error:

      if self.socket is not None:

        self.socket.close()

      self.socket = None

      raise

  def _CheckSocket(self):

    """Make sure we are connected.

    """

    if self.socket is None:

      raise ProtocolError("Connection is closed")

  def Send(self, msg):

    """Send a message.

    This just sends a message and doesn't wait for the response.

    """

    if self.eom in msg:

      raise EncodingError("Message terminator found in payload")

    self._CheckSocket()

    try:

      self.socket.sendall(msg + self.eom)

    except socket.timeout, err:

      raise TimeoutError("Sending timeout: %s" % str(err))

  def Recv(self):

    """Try to receive a messae from the socket.

    In case we already have messages queued, we just return from the

    queue. Otherwise, we try to read data with a _rwtimeout network

    timeout, and making sure we don't go over 2x_rwtimeout as a global

    limit.

    """

    self._CheckSocket()

    etime = time.time() + self._rwtimeout

    while not self._msgs:

      if time.time() > etime:

        raise TimeoutError("Extended receive timeout")

      try:

        data = self.socket.recv(4096)

      except socket.timeout, err:

        raise TimeoutError("Receive timeout: %s" % str(err))

      if not data:

        raise ConnectionClosedError("Connection closed while reading")

      new_msgs = (self._buffer + data).split(self.eom)

      self._buffer = new_msgs.pop()

      self._msgs.extend(new_msgs)

    return self._msgs.popleft()

  def Call(self, msg):

    """Send a message and wait for the response.

    This is just a wrapper over Send and Recv.

    """

    self.Send(msg)

    return self.Recv()

  def Close(self):

    """Close the socket"""

    if self.socket is not None:

      self.socket.close()

      self.socket = None

class Client(object):

  """High-level client implementation.

  This uses a backing Transport-like class on top of which it

  implements data serialization/deserialization.

  """

  def __init__(self, address, timeouts=None, transport=Transport):

    """Constructor for the Client class.

    Arguments:

      - address: a valid address the the used transport class

      - timeout: a list of timeouts, to be used on connect and read/write

      - transport: a Transport-like class

    If timeout is not passed, the default timeouts of the transport

    class are used.

    """

    self.transport = transport(address, timeouts=timeouts)

  def SendRequest(self, request, data):

    """Send a generic request and return the response.

    """

    msg = {KEY_REQUEST: request, KEY_DATA: data}

    result = self.transport.Call(simplejson.dumps(msg))

    try:

      data = simplejson.loads(result)

    except Exception, err:

      raise ProtocolError("Error while deserializing response: %s" % str(err))

    return data

  def SubmitJob(self, job):

    """Submit a job"""

    return self.SendRequest(REQ_SUBMIT, SerializeJob(job))

  def Query(self, data):

    """Make a query"""

    return self.SendRequest(REQ_QUERY, data)