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