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 import xml_

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 = xml_.xml2ele(self._raw) # <rpc-reply> element

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

        ok = xml_.find(root, 'ok', nslist=[xml_.BASE_NS, xml_.CISCO_BS])

        if ok is not None:

            logger.debug('parsed [%s]' % ok.tag)

        else: # create RPCError objects from <rpc-error> elements

            error = xml_.find(root, 'rpc-error', nslist=[xml_.BASE_NS, xml_.CISCO_BS])

            if error is not None:

                logger.debug('parsed [%s]' % error.tag)

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

                    # process a particular <rpc-error>

                    d = {}

                    for err_detail in err.getchildren(): # <error-type> etc..

                        tag = xml_.unqualify(err_detail.tag)

                        if tag != 'error-info':

                            d[tag] = err_detail.text.strip()

                        else:

                            d[tag] = xml_.ele2xml(err_detail)

                    self._errors.append(RPCError(d))

        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): # raise it if you like

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

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

    def __init__(self, err_dict):

        self._dict = err_dict

        if self.message is not None:

            OperationError.__init__(self, self.message)

        else:

            OperationError.__init__(self)

    @property

    def type(self):

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

        return self.get('error-type', None)

    @property

    def severity(self):

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

        return self.get('error-severity', None)

    @property

    def tag(self):

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

        return self.get('error-tag', None)

    @property

    def path(self):

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

        return self.get('error-path', None)

    @property

    def message(self):

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

        return self.get('error-message', None)

    @property

    def info(self):

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

        return self.get('error-info', None)

    ## dictionary interface

    __getitem__ = lambda self, key: self._dict.__getitem__(key)

    __iter__ = lambda self: self._dict.__iter__()

    __contains__ = lambda self, key: self._dict.__contains__(key)

    keys = lambda self: self._dict.keys()

    get = lambda self, key, default: self._dict.get(key, default)

    iteritems = lambda self: self._dict.iteritems()

    iterkeys = lambda self: self._dict.iterkeys()

    itervalues = lambda self: self._dict.itervalues()

    values = lambda self: self._dict.values()

    items = lambda self: self._dict.items()

    __repr__ = lambda self: repr(self._dict)

class RPCReplyListener(SessionListener):

    # internal use

    # one instance per session

    def __new__(cls, session):

        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 xml_.unqualify(tag) != 'rpc-reply':

            return

        rpc = None

        for key in attrs:

            if xml_.unqualify(key) == 'message-id':

                id = attrs[key]

                try:

                    with self._lock:

                        rpc = self._id2rpc.pop(id)

                except KeyError:

                    logger.warning('no object registered for message-id: [%s]' % id)

                except Exception as e:

                    logger.debug('error - %r' % e)

                break

        else:

            if not self._pipelined:

                with self._lock:

                    assert(len(self._id2rpc) == 1)

                    rpc = self._id2rpc.values()[0]

                    self._id2rpc.clear()

            else:

                logger.warning('<rpc-reply> without message-id received: %s' % raw)

        logger.debug('delivering to %r' % rpc)

        rpc.deliver_reply(raw)

    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):

        self._session = session

        try:

            for cap in self.DEPENDS:

                self._assert(cap)

        except AttributeError:

            pass

        self._async = async

        self._timeout = timeout

        # keeps things simple instead of having a class attr that has to be locked

        self._id = uuid1().urn

        # RPCReplyListener itself makes sure there isn't more than one instance -- i.e. multiton

        self._listener = RPCReplyListener(session)

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

        self._reply = None

        self._error = None

        self._event = Event()

    def _build(self, opspec):

        # internal

        spec = {

            'tag': 'rpc',

            'attrib': {

                'xmlns': xml_.BASE_NS,

                'message-id': self._id

                },

            'subtree': [ opspec ]

            }

        return xml_.dtree2xml(spec)

    def _request(self, op):

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

        In asynchronous mode, returns an :class:`~threading.Event` which is set

        when the reply has been received or an error occured. It is prudent,

        therefore, to check the :attr:`error` attribute before accesing

        :attr:`reply`.

        Otherwise, waits until the reply is received and returns

        :class:`RPCReply`.

        :arg opspec: :ref:`dtree` for the operation

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

        :rtype: :class:`~threading.Event` or :class:`RPCReply`

        """

        logger.debug('request %r with opsepc=%r' % (self, op))

        req = self._build(op)

        self._session.send(req)

        if self._async:

            logger.debug('async, returning event')

            return self._event

        else:

            logger.debug('sync, will wait for timeout=%r' % self._timeout)

            self._event.wait(self._timeout)

            if self._event.isSet():

                if self._error:

                    raise self._error

                self._reply.parse()

                return self._reply

            else:

                raise TimeoutExpiredError

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

        """Subclasses implement this method. Here, the operation is constructed

        in :ref:`dtree`, and the result of :meth:`_request` returned."""

        raise NotImplementedError

    def _delivery_hook(self):

        """Subclasses can implement this method. Will be called after

        initialising the :attr:`reply` or :attr:`error` attribute and before

        setting the :attr:`event`"""

        pass

    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._delivery_hook()

        self._event.set()

    def deliver_error(self, err):

        # internal use

        self._error = err

        self._delivery_hook()

        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`.

        This attribute should be checked if the request was made asynchronously,

        so that it can be determined if :attr:`event` being set is because of a

        reply or error.

        .. 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_timeout(self, timeout):

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

        request will block on a reply before raising an error."""

        self._timeout = timeout

    #: Whether this RPC is asynchronous

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

    #: Timeout for synchronous waiting

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