root / lib / rpc / transport.py @ f3aebf6f
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# Copyright (C) 2013 Google Inc.
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful, but
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# WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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# 02110-1301, USA.
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"""Module that defines a transport for RPC connections.
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A transport can send to and receive messages from some endpoint.
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"""
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import collections |
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import errno |
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import logging |
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import socket |
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import time |
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from ganeti import constants |
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from ganeti import utils |
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from ganeti.rpc import errors |
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DEF_CTMO = constants.LUXI_DEF_CTMO |
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DEF_RWTO = constants.LUXI_DEF_RWTO |
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class Transport: |
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"""Low-level transport class.
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This is used on the client side.
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This could be replace by any other class that provides the same
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semantics to the Client. This means:
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- can send messages and receive messages
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- safe for multithreading
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"""
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def __init__(self, address, timeouts=None): |
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"""Constructor for the Client class.
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Arguments:
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- address: a valid address the the used transport class
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- timeout: a list of timeouts, to be used on connect and read/write
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There are two timeouts used since we might want to wait for a long
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time for a response, but the connect timeout should be lower.
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If not passed, we use a default of 10 and respectively 60 seconds.
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Note that on reading data, since the timeout applies to an
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invidual receive, it might be that the total duration is longer
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than timeout value passed (we make a hard limit at twice the read
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timeout).
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"""
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self.address = address
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if timeouts is None: |
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self._ctimeout, self._rwtimeout = DEF_CTMO, DEF_RWTO |
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else:
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self._ctimeout, self._rwtimeout = timeouts |
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self.socket = None |
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self._buffer = "" |
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self._msgs = collections.deque()
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try:
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self.socket = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
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# Try to connect
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try:
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utils.Retry(self._Connect, 1.0, self._ctimeout, |
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args=(self.socket, address, self._ctimeout)) |
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except utils.RetryTimeout:
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raise errors.TimeoutError("Connect timed out") |
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self.socket.settimeout(self._rwtimeout) |
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except (socket.error, errors.NoMasterError):
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if self.socket is not None: |
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self.socket.close()
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self.socket = None |
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raise
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@staticmethod
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def _Connect(sock, address, timeout): |
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sock.settimeout(timeout) |
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try:
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sock.connect(address) |
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except socket.timeout, err:
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raise errors.TimeoutError("Connect timed out: %s" % str(err)) |
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except socket.error, err:
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error_code = err.args[0]
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if error_code in (errno.ENOENT, errno.ECONNREFUSED): |
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raise errors.NoMasterError(address)
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elif error_code in (errno.EPERM, errno.EACCES): |
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raise errors.PermissionError(address)
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elif error_code == errno.EAGAIN:
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# Server's socket backlog is full at the moment
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raise utils.RetryAgain()
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raise
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def _CheckSocket(self): |
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"""Make sure we are connected.
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"""
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if self.socket is None: |
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raise errors.ProtocolError("Connection is closed") |
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def Send(self, msg): |
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"""Send a message.
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This just sends a message and doesn't wait for the response.
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"""
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if constants.LUXI_EOM in msg: |
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raise errors.ProtocolError("Message terminator found in payload") |
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self._CheckSocket()
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try:
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# TODO: sendall is not guaranteed to send everything
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self.socket.sendall(msg + constants.LUXI_EOM)
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except socket.timeout, err:
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raise errors.TimeoutError("Sending timeout: %s" % str(err)) |
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def Recv(self): |
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"""Try to receive a message from the socket.
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In case we already have messages queued, we just return from the
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queue. Otherwise, we try to read data with a _rwtimeout network
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timeout, and making sure we don't go over 2x_rwtimeout as a global
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limit.
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"""
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self._CheckSocket()
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etime = time.time() + self._rwtimeout
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while not self._msgs: |
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if time.time() > etime:
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raise errors.TimeoutError("Extended receive timeout") |
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while True: |
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try:
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data = self.socket.recv(4096) |
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except socket.timeout, err:
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raise errors.TimeoutError("Receive timeout: %s" % str(err)) |
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except socket.error, err:
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if err.args and err.args[0] == errno.EAGAIN: |
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continue
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raise
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break
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if not data: |
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raise errors.ConnectionClosedError("Connection closed while reading") |
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new_msgs = (self._buffer + data).split(constants.LUXI_EOM)
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self._buffer = new_msgs.pop()
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self._msgs.extend(new_msgs)
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return self._msgs.popleft() |
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def Call(self, msg): |
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"""Send a message and wait for the response.
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This is just a wrapper over Send and Recv.
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"""
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self.Send(msg)
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return self.Recv() |
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@staticmethod
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def RetryOnBrokenPipe(fn, on_error): |
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"""Calls a given function, retrying if it fails on the 'Broken pipe' IO
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exception.
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This allows to re-establish a broken connection and retry an IO operation.
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The function receives one an integer argument stating the current retry
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number, 0 being the first call, 1 being the retry.
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If any exception occurs, on_error is invoked first with the exception given
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as an argument. Then, if the exception is 'Broken pipe', the function call
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is retried once more.
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"""
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retries = 2
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for try_no in range(0, retries): |
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try:
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return fn(try_no)
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except socket.error, ex:
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on_error(ex) |
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# we retry on "Broken pipe", unless it's the last try
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if try_no == retries - 1: |
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raise
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elif not (isinstance(ex.args, tuple) and (ex[0] == errno.EPIPE)): |
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raise
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except Exception, ex: |
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on_error(ex) |
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raise
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assert False # we should never get here |
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def Close(self): |
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"""Close the socket"""
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if self.socket is not None: |
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self.socket.close()
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self.socket = None |