pvc/client-common/zkhandler.py

76 lines
2.4 KiB
Python

#!/usr/bin/env python3
# zkhandler.py - Secure versioned ZooKeeper updates
# Part of the Parallel Virtual Cluster (PVC) system
#
# Copyright (C) 2018 Joshua M. Boniface <joshua@boniface.me>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <https://www.gnu.org/licenses/>.
#
###############################################################################
import kazoo.client
import client_lib.ansiiprint as ansiiprint
# Child list function
def listchildren(zk_conn, key):
children = zk_conn.get_children(key)
return children
# Data read function
def readdata(zk_conn, key):
data_raw = zk_conn.get(key)
data = data_raw[0].decode('ascii')
meta = data_raw[1]
return data
# Data write function
def writedata(zk_conn, kv):
# Start up a transaction
zk_transaction = zk_conn.transaction()
# Proceed one KV pair at a time
for key in sorted(kv):
data = kv[key]
# Check if this key already exists or not
if not zk_conn.exists(key):
# We're creating a new key
zk_transaction.create(key, str(data).encode('ascii'))
else:
# We're updating a key with version validation
orig_data = zk_conn.get(key)
version = orig_data[1].version
# Set what we expect the new version to be
new_version = version + 1
# Update the data
zk_transaction.set_data(key, str(data).encode('ascii'))
# Set up the check
try:
zk_transaction.check(key, new_version)
except TypeError:
print('Zookeeper key "{}" does not match expected version'.format(key))
return False
# Commit the transaction
try:
zk_transaction.commit()
return True
except Exception:
return False