zhmcclient/_auto_updater.py
#!/usr/bin/env python
# Copyright 2021 IBM Corp. All Rights Reserved.
#
# 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.
"""
Support for the :ref:`auto-updating` of Python zhmcclient resource and manager
objects based on HMC notifications.
"""
import logging
import json
try:
from json import JSONDecodeError as _JSONDecodeError
except ImportError:
_JSONDecodeError = ValueError
from ._constants import DEFAULT_STOMP_PORT, JMS_LOGGER_NAME
from ._utils import RC_CPC, RC_CHILDREN_CLIENT, RC_CHILDREN_CPC, \
RC_CHILDREN_CONSOLE
from ._client import Client
from ._manager import BaseManager
from ._resource import BaseResource
__all__ = ['AutoUpdater']
JMS_LOGGER = logging.getLogger(JMS_LOGGER_NAME)
class AutoUpdater(object):
"""
A class that automatically updates
* the properties of zhmcclient resource objects that are enabled for
auto-updating
* the list of zhmcclient resource objects in manager objects that are
enabled for auto-updating
based on respective notifications from the HMC.
**Experimental:** This class is considered experimental at this point, and
its API may change incompatibly as long as it is experimental.
Note: The user should not create any objects of this class nor invoke any
methods of this class, because the objects are created automatically
when a :class:`~zhmcclient.Session` object is subscribed for
auto-updating via its :meth:`~zhmcclient.Session.subscribe_auto_update`
method.
Creating an object of this class performs a logon to the HMC to retrieve
the notification topics, and then establishes a JMS session with the HMC and
subscribes for the object notification topic of the session. This causes
the HMC to emit status notifications, property notifications, and inventory
notifications, which are processed by this class and cause the updates
to happen.
Resource objects can be enabled for auto-updating via their
:meth:`~zhmcclient.BaseResource.enable_auto_update` method.
Manager objects can be enabled for auto-updating via their
:meth:`~zhmcclient.BaseManager.enable_auto_update` method.
Zhmcclient resource objects or manager objects that are not enabled for
auto-updating remain unchanged.
"""
def __init__(self, session):
"""
Parameters:
session (:class:`~zhmcclient.Session`): Session for which the
auto updater should do its work. This defines the HMC host
and credentials that are used to establish the JMS session with
the HMC. The session may or may not be logged on.
"""
self._session = session
# Stomp_Connection
self._conn = None
# Registered resource and manager objects, as:
# dict(key: uri, value: dict(key: id, value: object))
self._registered_objects = {}
# Subscription ID. We use some value that allows to identify on the
# HMC that this is the zhmcclient, but otherwise we are not using
# this value ourselves.
self._sub_id = 'zhmcclient.{}'.format(id(self))
def open(self):
"""
Open the JMS session with the HMC.
This creates a STOMP connection with the actual HMC of the session and
subscribes to the object notification topic.
If the session does not yet have an object notification topic set,
the session is logged on.
"""
# Lazy importing for stomp, because it is so slow (ca. 5 sec)
if 'Stomp_Connection' not in globals():
# pylint: disable=import-outside-toplevel
from stomp import Connection as Stomp_Connection
if not self._session.object_topic:
self._session.logon() # This sets actual_host
self._conn = Stomp_Connection(
[(self._session.actual_host, DEFAULT_STOMP_PORT)], use_ssl="SSL")
listener = _UpdateListener(self, self._session)
self._conn.set_listener('', listener)
# pylint: disable=protected-access
self._conn.connect(self._session.userid, self._session._password,
wait=True)
dest = "/topic/" + self._session.object_topic
self._conn.subscribe(destination=dest, id=self._sub_id, ack='auto')
listener.init_cpcs()
JMS_LOGGER.info(
"JMS session for object notification topic '%s' has been "
"established", self._session.object_topic)
def close(self):
"""
Close the JMS session with the HMC.
This implicitly unsubscribes from the object notification topic this
auto updater was created for.
"""
self._conn.disconnect()
self._conn = None
JMS_LOGGER.info(
"JMS session for object notification topic '%s' has been "
"disconnected", self._session.object_topic)
def is_open(self):
"""
Return whether the JMS session with the HMC is open.
"""
return self._conn is not None
def register_object(self, obj):
"""
Register a resource or manager object to this auto updater.
If this object (identified by its Python id) is already registered,
nothing is done.
"""
assert isinstance(obj, (BaseResource, BaseManager))
uri = obj.uri
res_id = id(obj)
if uri not in self._registered_objects:
self._registered_objects[uri] = {}
id_dict = self._registered_objects[uri]
if res_id not in id_dict:
id_dict[res_id] = obj
def unregister_object(self, obj):
"""
Unregister a resource or manager object from this auto updater.
If this object (identified by its Python id) is already unregistered,
nothing is done.
"""
assert isinstance(obj, (BaseResource, BaseManager))
uri = obj.uri
res_id = id(obj)
if uri in self._registered_objects:
id_dict = self._registered_objects[uri]
if res_id in id_dict:
del id_dict[res_id]
if not id_dict:
del self._registered_objects[uri]
def registered_objects(self, uri):
"""
Generator that yields the resource or manager objects for the specified
URI.
"""
if uri in self._registered_objects:
id_dict = self._registered_objects[uri]
# pylint: disable=use-yield-from
for res_obj in id_dict.values():
yield res_obj
def has_objects(self):
"""
Return boolean indicating whether there are any resource objects
registered.
"""
return bool(self._registered_objects)
class _UpdateListener(object):
# pylint: disable=too-few-public-methods
"""
A notification listener class for use by the Python `stomp` package.
This is an internal class that does not need to be accessed or created by
the user. An object of this class is automatically created by the
:class:`~zhmcclient.AutoUpdater` class, for its notification
topic.
Note: In the stomp examples, this class inherits from
stomp.ConnectionListener. However, since that class defines only empty
methods and since we want to import the stomp module in a lazy manner,
we are not using that class, and stomp does not require us to.
"""
def __init__(self, updater, session):
self._updater = updater
self._session = session
self._client = None
def init_cpcs(self):
"""
Initialize the CPC manager, for later use when receiving inventory
notifications for child objects of CPCs.
"""
if self._client is None:
self._client = Client(self._session)
self._client.cpcs.enable_auto_update()
def _manager_uri_from_notification(self, headers):
"""
Return the manager URI from the headers of an inventory notification
and the resource URI.
"""
try:
res_class = headers['class']
except KeyError:
JMS_LOGGER.error(
"JMS message for object notification topic '%s' "
"has no 'class' field in "
"its headers (ignored): %r",
self._session.object_topic, headers)
return None
if 'element-uri' in headers:
# The notification is about an element resource. In that case,
# 'object-uri' identifies the containing (=parent) object resource.
try:
parent_uris = [headers['object-uri']]
except KeyError:
JMS_LOGGER.error(
"JMS message for object notification topic '%s' "
"has an 'element-uri' field but no 'object-uri' field in "
"its headers (ignored): %r",
self._session.object_topic, headers)
return None
else:
# The notification is about an object (non-element) resource.
# The parent object's URI is not specified in the notification
# in this case, but there are not too many parent resources that
# have object resources as children, so we try to find it.
# In the removal case, it is not important what the parent
# resource is. We simply return all possible parent resources
# and the caller will look them all up to find the resource to
# be removed.
# In the addition case, it is important to find the parent object
# because only the parent object has the right manager object into
# which the new resource is added.
if res_class == RC_CPC:
# Could be a managed or unmanaged CPC
parent_uris = ['/api/console', '/']
elif res_class in RC_CHILDREN_CLIENT:
# RC_CHILDREN_CLIENT includes RC_CPC, but that is already
# processed
parent_uris = ['/']
elif res_class in RC_CHILDREN_CPC:
cpcs = self._client.cpcs.list_resources_local()
parent_uris = [cpc.uri for cpc in cpcs]
elif res_class in RC_CHILDREN_CONSOLE:
# RC_CHILDREN_CONSOLE includes RC_CPC, but that is already
# processed
parent_uris = ['/api/console']
else:
JMS_LOGGER.error(
"JMS message for object notification topic '%s' "
"has an unknown 'class' field in "
"its headers (ignored): %r",
self._session.object_topic, headers)
return None
mgr_uris = ['{}#{}'.format(_uri, res_class) for _uri in parent_uris]
return mgr_uris
def _get_uri(self, headers):
"""
Return the uri of the object or element resource o which the
notification applies.
If the notification is about an element resource, element-uri is
present and is the URI of that resource, and object-uri is the URI of
the parent (containing) object.
If the notification is about an object (=non-element) resource,
element-uri is not present, and object-uri is the URI of that
resource.
"""
if 'element-uri' in headers:
# The notification is about an element resource
uri = headers['element-uri']
else:
# The notification is about an object (non-element) resource
try:
uri = headers['object-uri']
except KeyError:
JMS_LOGGER.error(
"JMS message for object notification topic '%s' "
"has no 'element-uri' field and no 'object-uri' field in "
"its headers (ignored): %r",
self._session.object_topic, headers)
return None
return uri
def on_message(self, headers, message):
"""
Event method that gets called when this listener has received a JMS
message (representing an HMC notification).
Parameters:
headers (dict): JMS message headers, see HMC API book.
message (string): JMS message body as a string, which contains a
serialized JSON object, see HMC API book.
"""
noti_type = headers['notification-type']
if noti_type == 'property-change':
try:
msg_obj = json.loads(message)
except _JSONDecodeError:
JMS_LOGGER.error(
"JMS message for object notification topic '%s' "
"has a non-JSON message body (ignored): %r",
self._session.object_topic, message)
return
uri = self._get_uri(headers)
if uri is None:
# Some error - details are already logged
return
JMS_LOGGER.debug(
"JMS message for property change notification for topic '%s' "
"for resource %s with change reports: %r",
self._session.object_topic, uri, msg_obj['change-reports'])
# Build the latest values from all change records. They are ordered
# old to new.
new_props = {}
for cr in msg_obj['change-reports']:
new_props[cr['property-name']] = cr['new-value']
for obj in self._updater.registered_objects(uri):
if obj.auto_update_enabled():
obj.update_properties_local(new_props)
elif noti_type == 'status-change':
try:
msg_obj = json.loads(message)
except _JSONDecodeError:
JMS_LOGGER.error(
"JMS message for object notification topic '%s' "
"has a non-JSON message body (ignored): %r",
self._session.object_topic, message)
return
uri = self._get_uri(headers)
if uri is None:
# Some error - details are already logged
return
JMS_LOGGER.debug(
"JMS message for status change notification for topic '%s' "
"for resource %s with change reports: %r",
self._session.object_topic, uri, msg_obj['change-reports'])
# Build the latest values from all change records. They are ordered
# old to new.
new_props = {}
for cr in msg_obj['change-reports']:
if 'new-status' in cr:
new_props['status'] = cr['new-status']
if 'new-additional-status' in cr:
new_props['additional-status'] = cr['new-additional-status']
if 'has-unacceptable-status' in cr:
new_props['has-unacceptable-status'] = \
cr['has-unacceptable-status']
for obj in self._updater.registered_objects(uri):
if obj.auto_update_enabled():
obj.update_properties_local(new_props)
elif noti_type == 'inventory-change':
uri = self._get_uri(headers)
if uri is None:
# Some error - details are already logged
return
action = headers['action']
JMS_LOGGER.debug(
"JMS message for inventory change notification for topic '%s' "
"for resource %s with action: %r",
self._session.object_topic, uri, action)
if action == 'add':
mgr_uris = self._manager_uri_from_notification(headers)
if mgr_uris is None:
# Some error - details are already logged
return
for mgr_uri in mgr_uris:
for mgr_obj in self._updater.registered_objects(mgr_uri):
if mgr_obj.auto_update_enabled():
mgr_obj.auto_update_trigger_pull()
elif action == 'remove':
mgr_uris = self._manager_uri_from_notification(headers)
if mgr_uris is None:
# Some error - details are already logged
return
for mgr_uri in mgr_uris:
for mgr_obj in self._updater.registered_objects(mgr_uri):
if mgr_obj.auto_update_enabled():
mgr_obj.remove_resource_local(uri)
for obj in self._updater.registered_objects(uri):
if obj.auto_update_enabled():
obj.cease_existence_local()
else:
JMS_LOGGER.error(
"JMS message for inventory change notification specifies "
"unknown action %r (ignored)",
action)
else:
JMS_LOGGER.warning(
"JMS message for notification of type %s for topic '%s' "
"is ignored",
noti_type, self._session.object_topic)
def on_error(self, headers, message):
# pylint: disable=unused-argument
"""
Event method that gets called when this listener has received a JMS
error. This happens for example when the client registers for a
non-existing topic.
Parameters:
headers (dict): JMS message headers.
message (string): JMS message body as a string, which contains a
serialized JSON object.
"""
JMS_LOGGER.error(
"JMS error message received for object notification topic '%s' "
"(ignored): %s",
self._session.object_topic, message)
def on_disconnected(self):
"""
Event method that gets called when the JMS session has been
disconnected.
"""
JMS_LOGGER.info(
"JMS session for object notification topic '%s' has been "
"disconnected",
self._session.object_topic)