root / ncclient / operations / rpc.py @ 6e571704
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# Copyright 2009 Shikhar Bhushan
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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from threading import Event, Lock |
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from uuid import uuid1 |
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from ncclient.xml_ import * |
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from ncclient.transport import SessionListener |
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from errors import OperationError, TimeoutExpiredError, MissingCapabilityError |
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import logging |
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logger = logging.getLogger("ncclient.operations.rpc")
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class RPCError(OperationError): |
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"Represents an `rpc-error`. It is a type of :exc:`OperationError` and can be raised as such."
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tag_to_attr = { |
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qualify("error-type"): "_type", |
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qualify("error-tag"): "_tag", |
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qualify("error-severity"): "_severity", |
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qualify("error-info"): "_info", |
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qualify("error-path"): "_path", |
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qualify("error-message"): "_message" |
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} |
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def __init__(self, raw): |
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self._raw = raw
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for attr in RPCError.tag_to_attr.values(): |
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setattr(self, attr, None) |
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for subele in raw: |
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attr = RPCError.tag_to_attr.get(subele.tag, None)
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if attr is not None: |
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setattr(self, attr, subele.text if attr != "_info" else to_xml(subele) ) |
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if self.message is not None: |
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OperationError.__init__(self, self.message) |
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else:
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OperationError.__init__(self, self.to_dict()) |
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def to_dict(self): |
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return dict([ (attr[1:], getattr(self, attr)) for attr in RPCError.tag_to_attr.values() ]) |
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@property
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def xml(self): |
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"The `rpc-error` element as returned in XML."
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return self._raw |
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@property
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def type(self): |
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"The contents of the `error-type` element."
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return self._type |
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@property
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def tag(self): |
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"The contents of the `error-tag` element."
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return self._tag |
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@property
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def severity(self): |
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"The contents of the `error-severity` element."
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return self._severity |
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@property
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def path(self): |
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"The contents of the `error-path` element if present or `None`."
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return self._path |
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@property
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def message(self): |
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"The contents of the `error-message` element if present or `None`."
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return self._message |
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@property
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def info(self): |
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"XML string or `None`; representing the `error-info` element."
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return self._info |
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class RPCReply: |
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"""Represents an *rpc-reply*. Only concerns itself with whether the operation was successful.
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.. note::
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If the reply has not yet been parsed there is an implicit, one-time parsing overhead to
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accessing some of the attributes defined by this class.
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"""
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ERROR_CLS = RPCError |
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"Subclasses can specify a different error class, but it should be a subclass of `RPCError`."
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def __init__(self, raw): |
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self._raw = raw
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self._parsed = False |
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self._root = None |
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self._errors = []
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def __repr__(self): |
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return self._raw |
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def parse(self): |
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"Parses the *rpc-reply*."
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if self._parsed: return |
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root = self._root = to_ele(self._raw) # The <rpc-reply> element |
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# Per RFC 4741 an <ok/> tag is sent when there are no errors or warnings
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ok = root.find(qualify("ok"))
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if ok is None: |
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# Create RPCError objects from <rpc-error> elements
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error = root.find(qualify("rpc-error"))
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if error is not None: |
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for err in root.getiterator(error.tag): |
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# Process a particular <rpc-error>
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self._errors.append(self.ERROR_CLS(err)) |
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self._parsing_hook(root)
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self._parsed = True |
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def _parsing_hook(self, root): |
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"No-op by default. Gets passed the *root* element for the reply."
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pass
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@property
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def xml(self): |
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"*rpc-reply* element as returned."
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return self._raw |
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@property
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def ok(self): |
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"Boolean value indicating if there were no errors."
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return not self.errors # empty list => false |
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@property
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def error(self): |
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"Returns the first :class:`RPCError` and `None` if there were no errors."
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self.parse()
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if self._errors: |
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return self._errors[0] |
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else:
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return None |
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@property
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def errors(self): |
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"List of `RPCError` objects. Will be empty if there were no *rpc-error* elements in reply."
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self.parse()
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return self._errors |
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class RPCReplyListener(SessionListener): # internal use |
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creation_lock = Lock() |
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# one instance per session -- maybe there is a better way??
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def __new__(cls, session): |
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with RPCReplyListener.creation_lock:
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instance = session.get_listener_instance(cls) |
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if instance is None: |
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instance = object.__new__(cls)
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instance._lock = Lock() |
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instance._id2rpc = {} |
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#instance._pipelined = session.can_pipeline
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session.add_listener(instance) |
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return instance
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def register(self, id, rpc): |
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with self._lock: |
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self._id2rpc[id] = rpc |
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def callback(self, root, raw): |
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tag, attrs = root |
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if tag != qualify("rpc-reply"): |
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return
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for key in attrs: # in the <rpc-reply> attributes |
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if key == "message-id": # if we found msgid attr |
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id = attrs[key] # get the msgid
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with self._lock: |
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try:
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rpc = self._id2rpc[id] # the corresponding rpc |
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logger.debug("Delivering to %r" % rpc)
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rpc.deliver_reply(raw) |
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except KeyError: |
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raise OperationError("Unknown 'message-id': %s", id) |
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# no catching other exceptions, fail loudly if must
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else:
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# if no error delivering, can del the reference to the RPC
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del self._id2rpc[id] |
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break
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else:
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raise OperationError("Could not find 'message-id' attribute in <rpc-reply>") |
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def errback(self, err): |
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try:
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for rpc in self._id2rpc.values(): |
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rpc.deliver_error(err) |
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finally:
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self._id2rpc.clear()
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class RaiseMode(object): |
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NONE = 0
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"Don't attempt to raise any type of `rpc-error` as :exc:`RPCError`."
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ERRORS = 1
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"Raise only when the `error-type` indicates it is an honest-to-god error."
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ALL = 2
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"Don't look at the `error-type`, always raise."
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class RPC(object): |
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"""Base class for all operations, directly corresponding to *rpc* requests. Handles making the request, and taking delivery of the reply."""
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DEPENDS = [] |
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"""Subclasses can specify their dependencies on capabilities as a list of URI's or abbreviated names, e.g. ':writable-running'. These are verified at the time of instantiation. If the capability is not available, :exc:`MissingCapabilityError` is raised."""
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REPLY_CLS = RPCReply |
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"By default :class:`RPCReply`. Subclasses can specify a :class:`RPCReply` subclass."
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def __init__(self, session, async=False, timeout=30, raise_mode=RaiseMode.NONE): |
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"""
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*session* is the :class:`~ncclient.transport.Session` instance
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*async* specifies whether the request is to be made asynchronously, see :attr:`is_async`
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*timeout* is the timeout for a synchronous request, see :attr:`timeout`
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*raise_mode* specifies the exception raising mode, see :attr:`raise_mode`
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"""
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self._session = session
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try:
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for cap in self.DEPENDS: |
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self._assert(cap)
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except AttributeError: |
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pass
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self._async = async
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self._timeout = timeout
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self._raise_mode = raise_mode
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self._id = uuid1().urn # Keeps things simple instead of having a class attr with running ID that has to be locked |
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self._listener = RPCReplyListener(session)
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self._listener.register(self._id, self) |
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self._reply = None |
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self._error = None |
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self._event = Event()
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def _wrap(self, subele): |
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# internal use
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ele = new_ele("rpc", {"message-id": self._id}) |
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ele.append(subele) |
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return to_xml(ele)
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def _request(self, op): |
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"""Implementations of :meth:`request` call this method to send the request and process the reply.
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In synchronous mode, blocks until the reply is received and returns :class:`RPCReply`. Depending on the :attr:`raise_mode` a `rpc-error` element in the reply may lead to an :exc:`RPCError` exception.
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In asynchronous mode, returns immediately, returning `self`. The :attr:`event` attribute will be set when the reply has been received (see :attr:`reply`) or an error occured (see :attr:`error`).
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*op* is the operation to be requested as an :class:`~xml.etree.ElementTree.Element`
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"""
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logger.info('Requesting %r' % self.__class__.__name__) |
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req = self._wrap(op)
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self._session.send(req)
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if self._async: |
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logger.debug('Async request, returning %r', self) |
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return self |
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else:
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logger.debug('Sync request, will wait for timeout=%r' % self._timeout) |
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self._event.wait(self._timeout) |
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if self._event.isSet(): |
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if self._error: |
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# Error that prevented reply delivery
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raise self._error |
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self._reply.parse()
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if self._reply.error is not None: |
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# <rpc-error>'s [ RPCError ]
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if self._raise_mode == RaiseMode.ALL: |
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raise self._reply.error |
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elif (self._raise_mode == RaiseMode.ERRORS and self._reply.error.type == "error"): |
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raise self._reply.error |
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return self._reply |
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else:
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raise TimeoutExpiredError
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def request(self): |
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"""Subclasses must implement this method. Typically only the request needs to be built as an
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:class:`~xml.etree.ElementTree.Element` and everything else can be handed off to
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:meth:`_request`."""
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pass
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def _assert(self, capability): |
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"""Subclasses can use this method to verify that a capability is available with the NETCONF
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server, before making a request that requires it. A :exc:`MissingCapabilityError` will be
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raised if the capability is not available."""
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if capability not in self._session.server_capabilities: |
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raise MissingCapabilityError('Server does not support [%s]' % capability) |
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def deliver_reply(self, raw): |
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# internal use
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self._reply = self.REPLY_CLS(raw) |
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self._event.set()
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def deliver_error(self, err): |
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# internal use
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self._error = err
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self._event.set()
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@property
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def reply(self): |
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":class:`RPCReply` element if reply has been received or `None`"
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return self._reply |
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@property
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def error(self): |
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""":exc:`Exception` type if an error occured or `None`.
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.. note::
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This represents an error which prevented a reply from being received. An *rpc-error*
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does not fall in that category -- see `RPCReply` for that.
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"""
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return self._error |
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@property
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def id(self): |
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"The *message-id* for this RPC."
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return self._id |
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@property
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def session(self): |
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"The `~ncclient.transport.Session` object associated with this RPC."
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return self._session |
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@property
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def event(self): |
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""":class:`~threading.Event` that is set when reply has been received or when an error preventing
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delivery of the reply occurs.
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"""
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return self._event |
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def __set_async(self, async=True): |
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self._async = async
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if async and not session.can_pipeline: |
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raise UserWarning('Asynchronous mode not supported for this device/session') |
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def __set_raise_mode(self, mode): |
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assert(choice in ("all", "errors", "none")) |
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self._raise_mode = mode
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def __set_timeout(self, timeout): |
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self._timeout = timeout
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raise_mode = property(fget=lambda self: self._raise_mode, fset=__set_raise_mode) |
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"""Depending on this exception raising mode, an `rpc-error` in the reply may be raised as an :exc:`RPCError` exception. Valid values are the constants defined in :class:`RaiseMode`. """
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is_async = property(fget=lambda self: self._async, fset=__set_async) |
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"""Specifies whether this RPC will be / was requested asynchronously. By default RPC's are synchronous."""
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timeout = property(fget=lambda self: self._timeout, fset=__set_timeout) |
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"""Timeout in seconds for synchronous waiting defining how long the RPC request will block on a reply before raising :exc:`TimeoutExpiredError`.
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Irrelevant for asynchronous usage.
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"""
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