PySyncObj is a python library for building fault-tolerant distributed systems. It provides the ability to replicate your application data between multiple servers. It has following features:
- raft protocol for leader election and log replication
- Log compaction - it use fork for copy-on-write while serializing data on disk
- Dynamic membership changes - you can do it with syncobj_admin utility or directly from your code
- Zero downtime deploy - no need to stop cluster to update nodes
- In-memory and on-disk serialization - you can use in-memory mode for small data and on-disk for big one
- Encryption - you can set password and use it in external network
- Python2 and Python3 on linux, macos and windows - no dependencies required (only optional one, eg. cryptography)
- Configurable event loop - it can works in separate thread with it's own event loop - or you can call onTick function inside your own one
- Convenient interface - you can easily transform arbitrary class into a replicated one (see example below).
PySyncObj itself:
pip install pysyncobjCryptography for encryption (optional):
pip install cryptographyConsider you have a class that implements counter:
class MyCounter(object):
def __init__(self):
self.__counter = 0
def incCounter(self):
self.__counter += 1
def getCounter(self):
return self.__counterSo, to transform your class into a replicated one:
- Inherit it from SyncObj
- Initialize SyncObj with a self address and a list of partner addresses. Eg. if you have
serverA,serverBandserverCand want to use 4321 port, you should use self addressserverA:4321with partners[serverB:4321, serverC:4321]for your application, running atserverA; self addressserverB:4321with partners[serverA:4321, serverC:4321]for your application atserverB; self addressserverC:4321with partners[serverA:4321, serverB:4321]for app atserverC. - Mark all your methods that modifies your class fields with
@replicateddecorator. So your final class will looks like:
class MyCounter(SyncObj):
def __init__(self):
super(MyCounter, self).__init__('serverA:4321', ['serverB:4321', 'serverC:4321'])
self.__counter = 0
@replicated
def incCounter(self):
self.__counter += 1
def getCounter(self):
return self.__counterAnd thats all! Now you can call incCounter on serverA, and check counter value on serverB - they will be synchronized.
If you just need some distributed data structures - try built-in "batteries". Few examples:
from pysyncobj import SyncObj
from pysyncobj.batteries import ReplCounter, ReplDict
counter1 = ReplCounter()
counter2 = ReplCounter()
dict1 = ReplDict()
syncObj = SyncObj('serverA:4321', ['serverB:4321', 'serverC:4321'], consumers=[counter1, counter2, dict1])
counter1.set(42, sync=True) # set initial value to 42, 'sync' means that operation is blocking
counter1.add(10, sync=True) # add 10 to counter value
counter2.inc(sync=True) # increment counter value by one
dict1.set('testKey1', 'testValue1', sync=True)
dict1['testKey2'] = 'testValue2' # this is basically the same as previous, but asynchronous (non-blocking)
print(counter1, counter2, dict1['testKey1'], dict1.get('testKey2'))from pysyncobj import SyncObj
from pysyncobj.batteries import ReplLockManager
lockManager = ReplLockManager(timeout=75) # Lock will be released if connection dropped for more than 75 seconds
syncObj = SyncObj('serverA:4321', ['serverB:4321', 'serverC:4321'], consumers=[lockManager])
if lockManager.tryAcquire('testLockName', sync=True):
# do some actions
lockManager.release('testLockName')You can look at batteries implementation, examples and unit-tests for more use-cases. Also there is an API documentation. Feel free to create proposals and/or pull requests with new batteries, features, etc. Join our gitter chat if you have any questions.
