281 lines
9.0 KiB
Python
281 lines
9.0 KiB
Python
#!/usr/bin/env python
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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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import time
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from kazoo.client import KazooClient, KazooState
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from kazoo import exceptions as kze
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from kazoo.recipe.lock import Lock
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# States:
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# We are building this node but it is not ready for use.
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BUILDING = 'building'
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# The node is ready for use.
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READY = 'ready'
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# The node should be deleted.
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DELETING = 'deleting'
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STATES = set([BUILDING, READY, DELETING])
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class LockException(Exception):
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pass
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class ZooKeeperConnectionConfig(object):
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'''
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Represents the connection parameters for a ZooKeeper server.
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'''
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def __eq__(self, other):
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if isinstance(other, ZooKeeperConnectionConfig):
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if other.__dict__ == self.__dict__:
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return True
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return False
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def __init__(self, host, port=2181, chroot=None):
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'''Initialize the ZooKeeperConnectionConfig object.
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:param str host: The hostname of the ZooKeeper server.
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:param int port: The port on which ZooKeeper is listening.
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Optional, default: 2181.
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:param str chroot: A chroot for this connection. All
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ZooKeeper nodes will be underneath this root path.
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Optional, default: None.
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(one per server) defining the ZooKeeper cluster servers. Only
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the 'host' attribute is required.'.
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'''
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self.host = host
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self.port = port
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self.chroot = chroot or ''
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class ZooKeeper(object):
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'''
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Class implementing the ZooKeeper interface.
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This class uses the facade design pattern to keep common interaction
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with the ZooKeeper API simple and consistent for the caller, and
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limits coupling between objects. It allows for more complex interactions
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by providing direct access to the client connection when needed (though
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that is discouraged). It also provides for a convenient entry point for
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testing only ZooKeeper interactions.
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'''
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log = logging.getLogger("zuul.zk.ZooKeeper")
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REQUEST_ROOT = '/nodepool/requests'
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NODE_ROOT = '/nodepool/nodes'
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def __init__(self):
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'''
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Initialize the ZooKeeper object.
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'''
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self.client = None
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self._became_lost = False
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def _dictToStr(self, data):
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return json.dumps(data)
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def _strToDict(self, data):
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return json.loads(data)
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def _connection_listener(self, state):
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'''
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Listener method for Kazoo connection state changes.
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.. warning:: This method must not block.
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'''
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if state == KazooState.LOST:
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self.log.debug("ZooKeeper connection: LOST")
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self._became_lost = True
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elif state == KazooState.SUSPENDED:
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self.log.debug("ZooKeeper connection: SUSPENDED")
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else:
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self.log.debug("ZooKeeper connection: CONNECTED")
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@property
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def connected(self):
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return self.client.state == KazooState.CONNECTED
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@property
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def suspended(self):
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return self.client.state == KazooState.SUSPENDED
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@property
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def lost(self):
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return self.client.state == KazooState.LOST
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@property
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def didLoseConnection(self):
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return self._became_lost
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def resetLostFlag(self):
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self._became_lost = False
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def connect(self, host_list, read_only=False):
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'''
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Establish a connection with ZooKeeper cluster.
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Convenience method if a pre-existing ZooKeeper connection is not
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supplied to the ZooKeeper object at instantiation time.
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:param list host_list: A list of
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:py:class:`~nodepool.zk.ZooKeeperConnectionConfig` objects
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(one per server) defining the ZooKeeper cluster servers.
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:param bool read_only: If True, establishes a read-only connection.
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'''
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if self.client is None:
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self.client = KazooClient(hosts=host_list, read_only=read_only)
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self.client.add_listener(self._connection_listener)
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self.client.start()
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def disconnect(self):
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'''
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Close the ZooKeeper cluster connection.
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You should call this method if you used connect() to establish a
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cluster connection.
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'''
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if self.client is not None and self.client.connected:
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self.client.stop()
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self.client.close()
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self.client = None
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def resetHosts(self, host_list):
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'''
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Reset the ZooKeeper cluster connection host list.
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:param list host_list: A list of
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:py:class:`~nodepool.zk.ZooKeeperConnectionConfig` objects
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(one per server) defining the ZooKeeper cluster servers.
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'''
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if self.client is not None:
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self.client.set_hosts(hosts=host_list)
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def submitNodeRequest(self, node_request, watcher):
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'''
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Submit a request for nodes to Nodepool.
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:param NodeRequest node_request: A NodeRequest with the
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contents of the request.
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:param callable watcher: A callable object that will be
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invoked each time the request is updated. It is called
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with two arguments: (node_request, deleted) where
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node_request is the same argument passed to this method,
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and deleted is a boolean which is True if the node no
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longer exists (notably, this will happen on disconnection
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from ZooKeeper). The watcher should return False when
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further updates are no longer necessary.
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'''
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priority = 100 # TODO(jeblair): integrate into nodereq
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data = node_request.toDict()
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data['created_time'] = time.time()
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path = '%s/%s-' % (self.REQUEST_ROOT, priority)
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path = self.client.create(path, self._dictToStr(data),
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makepath=True,
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sequence=True, ephemeral=True)
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reqid = path.split("/")[-1]
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node_request.id = reqid
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def callback(data, stat):
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if data:
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data = self._strToDict(data)
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node_request.updateFromDict(data)
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request_nodes = node_request.nodeset.getNodes()
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for i, nodeid in enumerate(data.get('nodes', [])):
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node_path = '%s/%s' % (self.NODE_ROOT, nodeid)
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node_data, node_stat = self.client.get(node_path)
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node_data = self._strToDict(node_data)
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request_nodes[i].id = nodeid
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request_nodes[i].updateFromDict(node_data)
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deleted = (data is None) # data *are* none
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return watcher(node_request, deleted)
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self.client.DataWatch(path, callback)
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def deleteNodeRequest(self, node_request):
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'''
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Delete a request for nodes.
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:param NodeRequest node_request: A NodeRequest with the
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contents of the request.
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'''
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path = '%s/%s' % (self.REQUEST_ROOT, node_request.id)
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try:
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self.client.delete(path)
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except kze.NoNodeError:
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pass
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def storeNode(self, node):
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'''Store the node.
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The node is expected to already exist and is updated in its
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entirety.
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:param Node node: The node to update.
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'''
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path = '%s/%s' % (self.NODE_ROOT, node.id)
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self.client.set(path, self._dictToStr(node.toDict()))
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def lockNode(self, node, blocking=True, timeout=None):
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'''
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Lock a node.
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This should be called as soon as a request is fulfilled and
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the lock held for as long as the node is in-use. It can be
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used by nodepool to detect if Zuul has gone offline and the
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node should be reclaimed.
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:param Node node: The node which should be locked.
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'''
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lock_path = '%s/%s/lock' % (self.NODE_ROOT, node.id)
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try:
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lock = Lock(self.client, lock_path)
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have_lock = lock.acquire(blocking, timeout)
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except kze.LockTimeout:
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raise LockException(
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"Timeout trying to acquire lock %s" % lock_path)
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# If we aren't blocking, it's possible we didn't get the lock
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# because someone else has it.
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if not have_lock:
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raise LockException("Did not get lock on %s" % lock_path)
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node.lock = lock
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def unlockNode(self, node):
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'''
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Unlock a node.
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The node must already have been locked.
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:param Node node: The node which should be unlocked.
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'''
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if node.lock is None:
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raise LockException("Node %s does not hold a lock" % (node,))
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node.lock.release()
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node.lock = None
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