common.py

# vim: tabstop=4 shiftwidth=4 softtabstop=4

# Copyright 2010 United States Government as represented by the
# Administrator of the National Aeronautics and Space Administration.
# All Rights Reserved.
# Copyright 2011 Red Hat, Inc.
#
#    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.

import copy
import sys
import traceback

from openstack.common.gettextutils import _
from openstack.common import importutils
from openstack.common import jsonutils
from openstack.common import local
from openstack.common import log as logging


LOG = logging.getLogger(__name__)


class RPCException(Exception):
    message = _("An unknown RPC related exception occurred.")

    def __init__(self, message=None, **kwargs):
        self.kwargs = kwargs

        if not message:
            try:
                message = self.message % kwargs

            except Exception:
                # kwargs doesn't match a variable in the message
                # log the issue and the kwargs
                LOG.exception(_('Exception in string format operation'))
                for name, value in kwargs.iteritems():
                    LOG.error("%s: %s" % (name, value))
                # at least get the core message out if something happened
                message = self.message

        super(RPCException, self).__init__(message)


class RemoteError(RPCException):
    """Signifies that a remote class has raised an exception.

    Contains a string representation of the type of the original exception,
    the value of the original exception, and the traceback.  These are
    sent to the parent as a joined string so printing the exception
    contains all of the relevant info.

    """
    message = _("Remote error: %(exc_type)s %(value)s\n%(traceback)s.")

    def __init__(self, exc_type=None, value=None, traceback=None):
        self.exc_type = exc_type
        self.value = value
        self.traceback = traceback
        super(RemoteError, self).__init__(exc_type=exc_type,
                                          value=value,
                                          traceback=traceback)


class Timeout(RPCException):
    """Signifies that a timeout has occurred.

    This exception is raised if the rpc_response_timeout is reached while
    waiting for a response from the remote side.
    """
    message = _("Timeout while waiting on RPC response.")


class InvalidRPCConnectionReuse(RPCException):
    message = _("Invalid reuse of an RPC connection.")


class UnsupportedRpcVersion(RPCException):
    message = _("Specified RPC version, %(version)s, not supported by "
                "this endpoint.")


class Connection(object):
    """A connection, returned by rpc.create_connection().

    This class represents a connection to the message bus used for rpc.
    An instance of this class should never be created by users of the rpc API.
    Use rpc.create_connection() instead.
    """
    def close(self):
        """Close the connection.

        This method must be called when the connection will no longer be used.
        It will ensure that any resources associated with the connection, such
        as a network connection, and cleaned up.
        """
        raise NotImplementedError()

    def create_consumer(self, topic, proxy, fanout=False):
        """Create a consumer on this connection.

        A consumer is associated with a message queue on the backend message
        bus.  The consumer will read messages from the queue, unpack them, and
        dispatch them to the proxy object.  The contents of the message pulled
        off of the queue will determine which method gets called on the proxy
        object.

        :param topic: This is a name associated with what to consume from.
                      Multiple instances of a service may consume from the same
                      topic. For example, all instances of nova-compute consume
                      from a queue called "compute".  In that case, the
                      messages will get distributed amongst the consumers in a
                      round-robin fashion if fanout=False.  If fanout=True,
                      every consumer associated with this topic will get a
                      copy of every message.
        :param proxy: The object that will handle all incoming messages.
        :param fanout: Whether or not this is a fanout topic.  See the
                       documentation for the topic parameter for some
                       additional comments on this.
        """
        raise NotImplementedError()

    def create_worker(self, topic, proxy, pool_name):
        """Create a worker on this connection.

        A worker is like a regular consumer of messages directed to a
        topic, except that it is part of a set of such consumers (the
        "pool") which may run in parallel. Every pool of workers will
        receive a given message, but only one worker in the pool will
        be asked to process it. Load is distributed across the members
        of the pool in round-robin fashion.

        :param topic: This is a name associated with what to consume from.
                      Multiple instances of a service may consume from the same
                      topic.
        :param proxy: The object that will handle all incoming messages.
        :param pool_name: String containing the name of the pool of workers
        """
        raise NotImplementedError()

    def consume_in_thread(self):
        """Spawn a thread to handle incoming messages.

        Spawn a thread that will be responsible for handling all incoming
        messages for consumers that were set up on this connection.

        Message dispatching inside of this is expected to be implemented in a
        non-blocking manner.  An example implementation would be having this
        thread pull messages in for all of the consumers, but utilize a thread
        pool for dispatching the messages to the proxy objects.
        """
        raise NotImplementedError()


def _safe_log(log_func, msg, msg_data):
    """Sanitizes the msg_data field before logging."""
    SANITIZE = {'set_admin_password': ('new_pass',),
                'run_instance': ('admin_password',), }

    has_method = 'method' in msg_data and msg_data['method'] in SANITIZE
    has_context_token = '_context_auth_token' in msg_data
    has_token = 'auth_token' in msg_data

    if not any([has_method, has_context_token, has_token]):
        return log_func(msg, msg_data)

    msg_data = copy.deepcopy(msg_data)

    if has_method:
        method = msg_data['method']
        if method in SANITIZE:
            args_to_sanitize = SANITIZE[method]
            for arg in args_to_sanitize:
                try:
                    msg_data['args'][arg] = "<SANITIZED>"
                except KeyError:
                    pass

    if has_context_token:
        msg_data['_context_auth_token'] = '<SANITIZED>'

    if has_token:
        msg_data['auth_token'] = '<SANITIZED>'

    return log_func(msg, msg_data)


def serialize_remote_exception(failure_info, log_failure=True):
    """Prepares exception data to be sent over rpc.

    Failure_info should be a sys.exc_info() tuple.

    """
    tb = traceback.format_exception(*failure_info)
    failure = failure_info[1]
    if log_failure:
        LOG.error(_("Returning exception %s to caller"), unicode(failure))
        LOG.error(tb)

    kwargs = {}
    if hasattr(failure, 'kwargs'):
        kwargs = failure.kwargs

    data = {
        'class': str(failure.__class__.__name__),
        'module': str(failure.__class__.__module__),
        'message': unicode(failure),
        'tb': tb,
        'args': failure.args,
        'kwargs': kwargs
    }

    json_data = jsonutils.dumps(data)

    return json_data


def deserialize_remote_exception(conf, data):
    failure = jsonutils.loads(str(data))

    trace = failure.get('tb', [])
    message = failure.get('message', "") + "\n" + "\n".join(trace)
    name = failure.get('class')
    module = failure.get('module')

    # NOTE(ameade): We DO NOT want to allow just any module to be imported, in
    # order to prevent arbitrary code execution.
    if not module in conf.allowed_rpc_exception_modules:
        return RemoteError(name, failure.get('message'), trace)

    try:
        mod = importutils.import_module(module)
        klass = getattr(mod, name)
        if not issubclass(klass, Exception):
            raise TypeError("Can only deserialize Exceptions")

        failure = klass(**failure.get('kwargs', {}))
    except (AttributeError, TypeError, ImportError):
        return RemoteError(name, failure.get('message'), trace)

    ex_type = type(failure)
    str_override = lambda self: message
    new_ex_type = type(ex_type.__name__ + "_Remote", (ex_type,),
                       {'__str__': str_override, '__unicode__': str_override})
    try:
        # NOTE(ameade): Dynamically create a new exception type and swap it in
        # as the new type for the exception. This only works on user defined
        # Exceptions and not core python exceptions. This is important because
        # we cannot necessarily change an exception message so we must override
        # the __str__ method.
        failure.__class__ = new_ex_type
    except TypeError:
        # NOTE(ameade): If a core exception then just add the traceback to the
        # first exception argument.
        failure.args = (message,) + failure.args[1:]
    return failure


class CommonRpcContext(object):
    def __init__(self, **kwargs):
        self.values = kwargs

    def __getattr__(self, key):
        try:
            return self.values[key]
        except KeyError:
            raise AttributeError(key)

    def to_dict(self):
        return copy.deepcopy(self.values)

    @classmethod
    def from_dict(cls, values):
        return cls(**values)

    def deepcopy(self):
        return self.from_dict(self.to_dict())

    def update_store(self):
        local.store.context = self

    def elevated(self, read_deleted=None, overwrite=False):
        """Return a version of this context with admin flag set."""
        # TODO(russellb) This method is a bit of a nova-ism.  It makes
        # some assumptions about the data in the request context sent
        # across rpc, while the rest of this class does not.  We could get
        # rid of this if we changed the nova code that uses this to
        # convert the RpcContext back to its native RequestContext doing
        # something like nova.context.RequestContext.from_dict(ctxt.to_dict())

        context = self.deepcopy()
        context.values['is_admin'] = True

        context.values.setdefault('roles', [])

        if 'admin' not in context.values['roles']:
            context.values['roles'].append('admin')

        if read_deleted is not None:
            context.values['read_deleted'] = read_deleted

        return context


class ClientException(Exception):
    """This encapsulates some actual exception that is expected to be
    hit by an RPC proxy object. Merely instantiating it records the
    current exception information, which will be passed back to the
    RPC client without exceptional logging."""
    def __init__(self):
        self._exc_info = sys.exc_info()


def catch_client_exception(exceptions, func, *args, **kwargs):
    try:
        return func(*args, **kwargs)
    except Exception, e:
        if type(e) in exceptions:
            raise ClientException()
        else:
            raise


def client_exceptions(*exceptions):
    """Decorator for manager methods that raise expected exceptions.
    Marking a Manager method with this decorator allows the declaration
    of expected exceptions that the RPC layer should not consider fatal,
    and not log as if they were generated in a real error scenario. Note
    that this will cause listed exceptions to be wrapped in a
    ClientException, which is used internally by the RPC layer."""
    def outer(func):
        def inner(*args, **kwargs):
            return catch_client_exception(exceptions, func, *args, **kwargs)
        return inner
    return outer