ncclient:NETCONF Python client

# Copyright 2009 Shikhar Bhushan

#

# Licensed 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.

from threading import Event, Lock

from uuid import uuid1

from ncclient.xml_ import *

from ncclient.transport import SessionListener

from errors import OperationError, TimeoutExpiredError, MissingCapabilityError

import logging

logger = logging.getLogger("ncclient.operations.rpc")

class RPCReply:

    """Represents an *<rpc-reply>*. Only concerns itself with whether the

    operation was successful.

    .. note::

        If the reply has not yet been parsed there is an implicit, one-time

        parsing overhead to accessing the attributes defined by this class and

        any subclasses.

    """

    def __init__(self, raw):

        self._raw = raw

        self._parsed = False

        self._root = None

        self._errors = []

    def __repr__(self):

        return self._raw

    def _parsing_hook(self, root):

        """Subclass can implement.

        :type root: :class:`~xml.etree.ElementTree.Element`

        """

        pass

    def parse(self):

        """Parse the *<rpc-reply>*"""

        if self._parsed:

            return

        root = self._root = to_ele(self._raw) # The <rpc-reply> element

        # Per RFC 4741 an <ok/> tag is sent when there are no errors or warnings

        ok = root.find(qualify("ok"))

        if ok is None:

            # Create RPCError objects from <rpc-error> elements

            error = root.find(qualify("rpc-error"))

            if error is not None:

                for err in root.getiterator(error.tag):

                    # Process a particular <rpc-error>

                    self._errors.append(RPCError(err))

        self._parsing_hook(root)

        self._parsed = True

    @property

    def xml(self):

        "*<rpc-reply>* as returned"

        return self._raw

    @property

    def ok(self):

        "Boolean value indicating if there were no errors."

        if not self._parsed:

            self.parse()

        return not self._errors # empty list => false

    @property

    def error(self):

        """Short for :attr:`errors` [0]; :const:`None` if there were no errors.

        """

        if not self._parsed:

            self.parse()

        if self._errors:

            return self._errors[0]

        else:

            return None

    @property

    def errors(self):

        """`list` of :class:`RPCError` objects. Will be empty if there were no

        *<rpc-error>* elements in reply.

        """

        if not self._parsed:

            self.parse()

        return self._errors

class RPCError(OperationError):

    """Represents an *<rpc-error>*. It is a type of :exc:`OperationError`

    and can be raised like any other exception."""

    tag_to_attr = {

        qualify("error-type"): "_type",

        qualify("error-tag"): "_tag",

        qualify("error-severity"): "_severity",

        qualify("error-info"): "_info",

        qualify("error-path"): "_path",

        qualify("error-message"): "_message"

    }

    def __init__(self, err):

        for attr in tag_to_attr.values():

            setattr(self, attr, None)

        for subele in err:

            attr = tag_to_attr.get(subele.tag, None)

            if attr is not None:

                setattr(self, attr, subele.text)

        if self.message is not None:

            OperationError.__init__(self, self.message)

        else:

            OperationError.__init__(self, self.to_dict())

    def to_dict(self):

        return dict([ (attr[1:], gettattr(self, attr)) for attr in tag_to_attr.values() ])

    @property

    def type(self):

        "`string` representing text of *error-type* element"

        return self._type

    @property

    def tag(self):

        "`string` representing text of *error-tag* element"

        return self._tag

    @property

    def severity(self):

        "`string` representing text of *error-severity* element"

        return self._severity

    @property

    def path(self):

        "`string` or :const:`None`; representing text of *error-path* element"

        return self._path

    @property

    def message(self):

        "`string` or :const:`None`; representing text of *error-message* element"

        return self._message

    @property

    def info(self):

        "`string` (XML) or :const:`None`, representing *error-info* element"

        return self._info

class RPCReplyListener(SessionListener): # internal use

    creation_lock = Lock()

    # one instance per session -- maybe there is a better way??

    def __new__(cls, session):

        with creation_lock:

            instance = session.get_listener_instance(cls)

            if instance is None:

                instance = object.__new__(cls)

                instance._lock = Lock()

                instance._id2rpc = {}

                #instance._pipelined = session.can_pipeline

                session.add_listener(instance)

            return instance

    def register(self, id, rpc):

        with self._lock:

            self._id2rpc[id] = rpc

    def callback(self, root, raw):

        tag, attrs = root

        if tag != qualify("rpc-reply"):

            return

        for key in attrs: # in the <rpc-reply> attributes

            if key == "message-id": # if we found msgid attr

                id = attrs[key] # get the msgid

                with self._lock:

                    try:

                        rpc = self._id2rpc[id] # the corresponding rpc

                        logger.debug("Delivering to %r" % rpc)

                        rpc.deliver_reply(raw)

                    except KeyError:

                        raise OperationError("Unknown 'message-id': %s", id)

                    # no catching other exceptions, fail loudly if must

                    else:

                        # if no error delivering, can del the reference to the RPC

                        del self._id2rpc[id]

                        break

        else:

            raise OperationError("Could not find 'message-id' attribute in <rpc-reply>")

    def errback(self, err):

        try:

            for rpc in self._id2rpc.values():

                rpc.deliver_error(err)

        finally:

            self._id2rpc.clear()

class RPC(object):

    """Base class for all operations.

    Directly corresponds to *<rpc>* requests. Handles making the request, and

    taking delivery of the reply.

    """

    #: Subclasses can specify their dependencies on capabilities. List of URI's

    # or abbreviated names, e.g. ':writable-running'. These are verified at the

    # time of object creation. If the capability is not available, a

    # :exc:`MissingCapabilityError` is raised.

    DEPENDS = []

    #: Subclasses can specify a different reply class, but it must be a

    # subclass of :class:`RPCReply`.

    REPLY_CLS = RPCReply

    def __init__(self, session, async=False, timeout=None, raise_mode="none"):

        self._session = session

        try:

            for cap in self.DEPENDS:

                self._assert(cap)

        except AttributeError:

            pass

        self._async = async

        self._timeout = timeout

        self._raise_mode = raise_mode

        self._id = uuid1().urn # Keeps things simple instead of having a class attr that has to be locked

        self._listener = RPCReplyListener(session)

        self._listener.register(self._id, self)

        self._reply = None

        self._error = None

        self._event = Event()

    def _build(self, subele):

        # internal

        ele = new_ele("rpc", {"message-id": self._id}, xmlns=BASE_NS_1_0)

        ele.append(subele)

        return to_xml(ele)

    def _request(self, op):

        """Subclasses call this method to make the RPC request.

        In synchronous mode, waits until the reply is received and returns

        :class:`RPCReply`.

        In asynchronous mode, returns immediately, returning a reference to this

        object. The :attr:`event` attribute will be set when the reply has been

        received (see :attr:`reply`) or an error occured (see :attr:`error`).

        :type opspec: :obj:`dict` or :obj:`string` or :class:`~xml.etree.ElementTree.Element`

        :rtype: :class:`RPCReply` (sync) or :class:`RPC` (async)

        """

        logger.info('Requesting %r' % self.__class__.__name__)

        req = self._build(op)

        self._session.send(req)

        if self._async:

            logger.debug('Async request, returning %r', self)

            return self

        else:

            logger.debug('Sync request, will wait for timeout=%r' %

                         self._timeout)

            self._event.wait(self._timeout)

            if self._event.isSet():

                if self._error:

                    # Error that prevented reply delivery

                    raise self._error

                self._reply.parse()

                if self._reply.error is not None:

                    # <rpc-error>'s [ RPCError ]

                    if self._raise_mode == "all":

                        raise self._reply.error

                    elif (self._raise_mode == "errors" and

                          self._reply.error.type == "error"):

                        raise self._reply.error

                return self._reply

            else:

                raise TimeoutExpiredError

    def request(self, *args, **kwds):

        "Subclasses implement this method."

        return self._request(self.SPEC)

    def _assert(self, capability):

        """Subclasses can use this method to verify that a capability is available

        with the NETCONF server, before making a request that requires it. A

        :exc:`MissingCapabilityError` will be raised if the capability is not

        available."""

        if capability not in self._session.server_capabilities:

            raise MissingCapabilityError('Server does not support [%s]' %

                                         capability)

    def deliver_reply(self, raw):

        # internal use

        self._reply = self.REPLY_CLS(raw)

        self._event.set()

    def deliver_error(self, err):

        # internal use

        self._error = err

        self._event.set()

    @property

    def reply(self):

        ":class:`RPCReply` element if reply has been received or :const:`None`"

        return self._reply

    @property

    def error(self):

        """:exc:`Exception` type if an error occured or :const:`None`.

        .. note::

            This represents an error which prevented a reply from being

            received. An *<rpc-error>* does not fall in that category -- see

            :class:`RPCReply` for that.

        """

        return self._error

    @property

    def id(self):

        "The *message-id* for this RPC"

        return self._id

    @property

    def session(self):

        """The :class:`~ncclient.transport.Session` object associated with this

        RPC"""

        return self._session

    @property

    def event(self):

        """:class:`~threading.Event` that is set when reply has been received or

        error occured."""

        return self._event

    def set_async(self, async=True):

        """Set asynchronous mode for this RPC."""

        self._async = async

        if async and not session.can_pipeline:

            raise UserWarning('Asynchronous mode not supported for this device/session')

    def set_raise_mode(self, mode):

        assert(choice in ("all", "errors", "none"))

        self._raise_mode = mode

    def set_timeout(self, timeout):

        """Set the timeout for synchronous waiting; defining how long the RPC

        request will block on a reply before raising an error. Irrelevant for

        asynchronous usage."""

        self._timeout = timeout

    #: Whether this RPC is asynchronous

    is_async = property(fget=lambda self: self._async, fset=set_async)

    #: Timeout for synchronous waiting

    timeout = property(fget=lambda self: self._timeout, fset=set_timeout)