311 lines
10 KiB
Python
311 lines
10 KiB
Python
# Copyright 2020 BMW Group
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# 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, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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import json
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import logging
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from collections import defaultdict
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from kazoo.exceptions import NoNodeError
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from kazoo.protocol.states import EventType
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from zuul.zk import ZooKeeperBase
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COMPONENTS_ROOT = "/zuul/components"
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class BaseComponent(ZooKeeperBase):
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"""
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Read/write component object.
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This object holds an offline cache of all the component's attributes. In
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case of an failed update to ZooKeeper the local cache will still hold the
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fresh values. Updating any attribute uploads all attributes to ZooKeeper.
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This enables this object to be used as local key/value store even if the
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ZooKeeper connection got lost.
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:arg client ZooKeeperClient: The Zuul ZooKeeperClient object to use, or
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None if this should be a read-only component.
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:arg hostname str: The component's hostname (multiple components with
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the same hostname may be registered; the registry will create unique
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nodes for each).
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"""
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# Component states
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RUNNING = "running"
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PAUSED = "paused"
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STOPPED = "stopped"
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log = logging.getLogger("zuul.Component")
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kind = "base"
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def __init__(self, client, hostname):
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# Ensure that the content is available before setting any other
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# attribute, because our __setattr__ implementation is relying on it.
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self.__dict__["content"] = {
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"hostname": hostname,
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"state": self.STOPPED,
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"kind": self.kind,
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}
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super().__init__(client)
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self.path = None
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self._zstat = None
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def __getattr__(self, name):
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try:
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return self.content[name]
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except KeyError:
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raise AttributeError
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def __setattr__(self, name, value):
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# If the specified attribute is not part of our content dictionary,
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# fall back to the default __settattr__ behaviour.
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if name not in self.content.keys():
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return super().__setattr__(name, value)
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# Set the value in the local content dict
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self.content[name] = value
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if not self.path:
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self.log.error(
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"Path is not set on this component, did you forget to call "
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"register()?"
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)
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return
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# Update the ZooKeeper node
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content = json.dumps(self.content).encode("utf-8")
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try:
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zstat = self.kazoo_client.set(
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self.path, content, version=self._zstat.version
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)
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self._zstat = zstat
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except NoNodeError:
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self.log.error("Could not update %s in ZooKeeper", self)
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def register(self):
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path = "/".join([COMPONENTS_ROOT, self.kind, self.hostname])
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self.log.info("Registering component in ZooKeeper %s", path)
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self.path, self._zstat = self.kazoo_client.create(
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path,
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json.dumps(self.content).encode("utf-8"),
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makepath=True,
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ephemeral=True,
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sequence=True,
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# Also return the zstat, which is necessary to successfully update
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# the component.
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include_data=True,
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)
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def _onReconnect(self):
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self.register()
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def updateFromDict(self, data):
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self.content.update(data)
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@classmethod
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def fromDict(cls, client, hostname, data):
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component = cls(client, hostname)
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component.updateFromDict(data)
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return component
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def __repr__(self):
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return f"<{self.__class__.__name__} {self.content}>"
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class SchedulerComponent(BaseComponent):
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kind = "scheduler"
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class ExecutorComponent(BaseComponent):
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kind = "executor"
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def __init__(self, client, hostname):
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super().__init__(client, hostname)
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self.initial_state = {
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"accepting_work": False,
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"zone": None,
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"allow_unzoned": False,
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"process_merge_jobs": False,
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}
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self.content.update(self.initial_state)
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class MergerComponent(BaseComponent):
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kind = "merger"
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class FingerGatewayComponent(BaseComponent):
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kind = "fingergw"
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def __init__(self, client, hostname):
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super().__init__(client, hostname)
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self.initial_state = {
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"zone": None,
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"public_port": None,
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"use_ssl": False,
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}
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self.content.update(self.initial_state)
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class WebComponent(BaseComponent):
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kind = "web"
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class ComponentRegistry(ZooKeeperBase):
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"""A component registry is organized like:
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/zuul/components/{kind}/{sequence}
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Where kind corresponds to one of the classes in this module, and
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sequence is a ZK sequence node with a prefix of the hostname in
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order to produce a unique id for multiple identical components
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running on the same host. An example path:
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/zuul/components/scheduler/hostname0000000000
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Components are ephemeral nodes, and so if the actual service
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disconnects from ZK, the node will disappear.
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Component objects returned by this class are read-only; updating
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their attributes will not be reflected in ZooKeeper.
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"""
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log = logging.getLogger("zuul.ComponentRegistry")
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COMPONENT_CLASSES = {
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"scheduler": SchedulerComponent,
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"executor": ExecutorComponent,
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"merger": MergerComponent,
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"fingergw": FingerGatewayComponent,
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"web": WebComponent,
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}
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def __init__(self, client):
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super().__init__(client)
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self.client = client
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self._component_tree = None
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# kind -> hostname -> component
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self._cached_components = defaultdict(dict)
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# If we are already connected when the class is instantiated, directly
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# call the onConnect callback.
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if self.client.connected:
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self._onConnect()
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def _getComponentRoot(self, kind):
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return '/'.join([COMPONENTS_ROOT, kind])
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def _getComponentPath(self, kind, hostname):
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return '/'.join([COMPONENTS_ROOT, kind, hostname])
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def _onConnect(self):
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for kind in self.COMPONENT_CLASSES.keys():
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root = self._getComponentRoot(kind)
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self.kazoo_client.ensure_path(root)
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self.kazoo_client.ChildrenWatch(
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root, self._makeComponentRootWatcher(kind),
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send_event=True
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)
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def _makeComponentRootWatcher(self, kind):
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def watch(children, event=None):
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return self._onComponentRootUpdate(kind, children, event)
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return watch
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def _onComponentRootUpdate(self, kind, children, event):
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for hostname in children:
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component = self._cached_components[kind].get(hostname)
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if not component:
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self.log.info("Noticed new %s component %s", kind, hostname)
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root = self._getComponentPath(kind, hostname)
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self.kazoo_client.DataWatch(
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root, self._makeComponentWatcher(kind, hostname),
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send_event=True
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)
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def _makeComponentWatcher(self, kind, hostname):
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def watch(data, stat, event=None):
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return self._onComponentUpdate(kind, hostname, data, stat, event)
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return watch
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def _onComponentUpdate(self, kind, hostname, data, stat, event):
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if event:
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etype = event.type
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else:
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etype = None
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self.log.debug(
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"Registry %s got event %s for %s %s",
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self, etype, kind, hostname)
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if etype in (None, EventType.CHANGED, EventType.CREATED):
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# Ignore events without data
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if not data:
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return
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# Perform an in-place update of the cached component (if any)
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component = self._cached_components.get(kind, {}).get(hostname)
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d = json.loads(data.decode("utf-8"))
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self.log.info(
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"Component %s %s updated: %s",
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kind, hostname, d)
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if component:
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if (stat.version <= component._zstat.version):
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# Don't update to older data
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return
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component.updateFromDict(d)
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component._zstat = stat
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else:
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# Create a new component from the data structure
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# Get the correct kind of component
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# TODO (felix): KeyError on unknown component type?
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component_cls = self.COMPONENT_CLASSES[kind]
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# Pass in null ZK client to make a read-only component
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# instance.
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component = component_cls.fromDict(None, hostname, d)
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component.path = self._getComponentPath(kind, hostname)
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component._zstat = stat
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self._cached_components[kind][hostname] = component
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elif etype == EventType.DELETED:
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self.log.info(
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"Noticed %s component %s disappeared",
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kind, hostname)
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try:
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del self._cached_components[kind][hostname]
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except KeyError:
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# If it's already gone, don't care
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pass
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# Return False to stop the datawatch
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return False
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def all(self, kind=None):
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"""Returns a list of components.
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If kind is None, then a list of tuples is returned, with each tuple
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being (kind, [list of components]).
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:arg kind str: The type of component to look up in the registry, or
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None to return all kinds
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"""
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if kind is None:
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return [(kind, list(components.values()))
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for (kind, components) in self._cached_components.items()]
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# Filter the cached components for the given kind
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return self._cached_components.get(kind, {}).values()
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