shade/shade/task_manager.py

# Copyright (C) 2011-2013 OpenStack Foundation
#
# 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 abc
import sys
import threading
import time
import types

import keystoneauth1.exceptions
import simplejson
import six

from shade import _log
from shade import meta


@six.add_metaclass(abc.ABCMeta)
class Task(object):
    """Represent a task to be performed on an OpenStack Cloud.

    Some consumers need to inject things like rate-limiting or auditing
    around each external REST interaction. Task provides an interface
    to encapsulate each such interaction. Also, although shade itself
    operates normally in a single-threaded direct action manner, consuming
    programs may provide a multi-threaded TaskManager themselves. For that
    reason, Task uses threading events to ensure appropriate wait conditions.
    These should be a no-op in single-threaded applications.

    A consumer is expected to overload the main method.

    :param dict kw: Any args that are expected to be passed to something in
                    the main payload at execution time.
    """

    def __init__(self, **kw):
        self._exception = None
        self._traceback = None
        self._result = None
        self._response = None
        self._finished = threading.Event()
        self.args = kw
        self.requests = False
        self._request_id = None

    @abc.abstractmethod
    def main(self, client):
        """ Override this method with the actual workload to be performed """

    def done(self, result):
        if self.requests:
            self._response, self._result = result
        else:
            self._result = result
        self._finished.set()

    def exception(self, e, tb):
        self._exception = e
        self._traceback = tb
        self._finished.set()

    def wait(self, raw=False):
        self._finished.wait()

        if self._exception:
            six.reraise(type(self._exception), self._exception,
                        self._traceback)

        if raw:
            # Do NOT convert the result.
            return self._result

        # NOTE(Shrews): Since the client API might decide to subclass one
        # of these result types, we use isinstance() here instead of type().
        if (isinstance(self._result, list) or
            isinstance(self._result, types.GeneratorType)):
            return meta.obj_list_to_dict(
                self._result, request_id=self._request_id)
        elif (not isinstance(self._result, bool) and
              not isinstance(self._result, int) and
              not isinstance(self._result, float) and
              not isinstance(self._result, str) and
              not isinstance(self._result, set) and
              not isinstance(self._result, tuple) and
              not isinstance(self._result, types.GeneratorType)):
            return meta.obj_to_dict(self._result, request_id=self._request_id)
        else:
            return self._result

    def run(self, client):
        self._client = client
        try:
            # Retry one time if we get a retriable connection failure
            try:
                self.done(self.main(client))
            except keystoneauth1.exceptions.RetriableConnectionFailure:
                client.log.debug(
                    "Connection failure for {name}, retrying".format(
                        name=type(self).__name__))
                self.done(self.main(client))
            except Exception:
                raise
        except Exception as e:
            self.exception(e, sys.exc_info()[2])


class RequestTask(Task):

    # It's totally legit for calls to not return things
    result_key = None

    # keystoneauth1 throws keystoneauth1.exceptions.http.HttpError on !200
    def done(self, result):
        self._response = result

        try:
            result_json = self._response.json()
        except (simplejson.scanner.JSONDecodeError, ValueError) as e:
            result_json = self._response.text
            self._client.log.debug(
                'Could not decode json in response: {e}'.format(e=str(e)))
            self._client.log.debug(result_json)

        if self.result_key:
            self._result = result_json[self.result_key]
        else:
            self._result = result_json
        self._request_id = self._response.headers.get('x-openstack-request-id')
        self._finished.set()


class TaskManager(object):
    log = _log.setup_logging("shade.TaskManager")

    def __init__(self, client, name):
        self.name = name
        self._client = client

    def stop(self):
        """ This is a direct action passthrough TaskManager """
        pass

    def run(self):
        """ This is a direct action passthrough TaskManager """
        pass

    def submitTask(self, task, raw=False):
        """Submit and execute the given task.

        :param task: The task to execute.
        :param bool raw: If True, return the raw result as received from the
            underlying client call.
        """
        self.log.debug(
            "Manager %s running task %s" % (self.name, type(task).__name__))
        start = time.time()
        task.run(self._client)
        end = time.time()
        self.log.debug(
            "Manager %s ran task %s in %ss" % (
                self.name, type(task).__name__, (end - start)))
        return task.wait(raw)