PoC: Patroni on pure RAFT (#375)

* new node can join the cluster dynamically and become a part of consensus * it is also possible to join only Patroni cluster (without adding the node to the raft), just comment or remove `raft.self_addr` for that * when the node joins the cluster it is using values from `raft.partner_addrs` only for initial discovery. * It is possible to run Patroni and Postgres on two nodes plus one node with `patroni_raft_controller` (without Patroni and Postgres). In such setup one can temporarily lose one node without affecting the primary.
2026-01-27 18:20:05 +00:00 · 2020-07-29 15:34:44 +02:00
parent c42d507b82
commit bfbc4860d5
19 changed files with 884 additions and 89 deletions
--- a/.travis.yml
+++ b/.travis.yml
@@ -21,6 +21,8 @@ matrix:
    env: DCS="exhibitor" TEST_SUITE="behave"
  - python: "3.6"
    env: DCS="consul" TEST_SUITE="behave"
+  - python: "3.6"
+    env: DCS="raft" TEST_SUITE="behave"
  - python: "3.6"
    env: DCS="kubernetes" TEST_SUITE="behave"
 branches:
@@ -102,6 +104,10 @@ install:
            done&
        }

+        function get_raft() {
+            return 0
+        }
+
        attempt_num=1
        until get_${DCS}; do
            [[ $attempt_num -ge 3 ]] && exit 1
--- a/docs/ENVIRONMENT.rst
+++ b/docs/ENVIRONMENT.rst
@@ -87,6 +87,13 @@ Kubernetes
 -  **PATRONI\_KUBERNETES\_POD\_IP**: (optional) IP address of the pod Patroni is running in. This value is required when `PATRONI_KUBERNETES_USE_ENDPOINTS` is enabled and is used to populate the leader endpoint subsets when the pod's PostgreSQL is promoted.
 -  **PATRONI\_KUBERNETES\_PORTS**: (optional) if the Service object has the name for the port, the same name must appear in the Endpoint object, otherwise service won't work. For example, if your service is defined as ``{Kind: Service, spec: {ports: [{name: postgresql, port: 5432, targetPort: 5432}]}}``, then you have to set ``PATRONI_KUBERNETES_PORTS='[{"name": "postgresql", "port": 5432}]'`` and Patroni will use it for updating subsets of the leader Endpoint. This parameter is used only if `PATRONI_KUBERNETES_USE_ENDPOINTS` is set.

+Raft
+----
+
+-  **PATRONI\_RAFT\_SELF\_ADDR**: ``ip:port`` to listen on for Raft connections. If not set, the node will not participate in consensus.
+-  **PATRONI\_RAFT\_PARTNER\_ADDRS**: list of other Patroni nodes in the cluster in format ``"'ip1:port1','ip2:port2'"``. It is important to quote every single entity!
+-  **PATRONI\_RAFT\_DATA\_DIR**: directory where to store Raft log and snapshot. If not specified the current working directory is used.
+
 PostgreSQL
 ----------
 -  **PATRONI\_POSTGRESQL\_LISTEN**: IP address + port that Postgres listens to. Multiple comma-separated addresses are permitted, as long as the port component is appended after to the last one with a colon, i.e. ``listen: 127.0.0.1,127.0.0.2:5432``. Patroni will use the first address from this list to establish local connections to the PostgreSQL node.
--- a/docs/SETTINGS.rst
+++ b/docs/SETTINGS.rst
@@ -159,6 +159,35 @@ Kubernetes
 -  **pod\_ip**: (optional) IP address of the pod Patroni is running in. This value is required when `use_endpoints` is enabled and is used to populate the leader endpoint subsets when the pod's PostgreSQL is promoted.
 -  **ports**: (optional) if the Service object has the name for the port, the same name must appear in the Endpoint object, otherwise service won't work. For example, if your service is defined as ``{Kind: Service, spec: {ports: [{name: postgresql, port: 5432, targetPort: 5432}]}}``, then you have to set ``kubernetes.ports: [{"name": "postgresql", "port": 5432}]`` and Patroni will use it for updating subsets of the leader Endpoint. This parameter is used only if `kubernetes.use_endpoints` is set.

+Raft
+----
+-  **self\_addr**: ``ip:port`` to listen on for Raft connections. If not set, the node will not participate in consensus.
+-  **partner\_addrs**: list of other Patroni nodes in the cluster in format: ['ip1:port', 'ip2:port', 'etc...']
+-  **data\_dir**: directory where to store Raft log and snapshot. If not specified the current working directory is used.
+
+  Short FAQ about Raft implementation
+
+  - Q: How to list all the nodes providing consensus?
+
+    A: ``syncobj_admin -conn host:port`` -status where the host:port is the address of one of the cluster nodes
+
+  - Q: Node that was a part of consensus and has gone and I can't reuse the same IP for other node. How to remove this node from the consensus?
+
+    A: ``syncobj_admin -conn host:port -remove host2:port2`` where the ``host2:port2`` is the address of the node you want to remove from consensus.
+
+  - Q: Where to get the ``syncobj_admin`` utility?
+
+    A: It is installed together with ``pysyncobj`` module (python RAFT implementation), which is Patroni dependancy.
+
+  - Q: it is possible to run Patroni node without adding in to the consensus?
+
+    A: Yes, just comment out or remove ``raft.self_addr`` from Patroni configuration.
+
+  - Q: It is possible to run Patroni and PostgreSQL only on two nodes?
+
+    A: Yes, on the third node you can run ``patroni_raft_controller`` (without Patroni and PostgreSQL). In such setup one can temporary loose one node without affecting the primary.
+
+
 .. _postgresql_settings:

 PostgreSQL
--- a/features/environment.py
+++ b/features/environment.py
@@ -165,6 +165,11 @@ class PatroniController(AbstractController):
            config = yaml.safe_load(f)
            config.pop('etcd', None)

+        raft_port = os.environ.get('RAFT_PORT')
+        if raft_port:
+            os.environ['RAFT_PORT'] = str(int(raft_port) + 1)
+            config['raft'] = {'data_dir': self._output_dir, 'self_addr': 'localhost:' + os.environ['RAFT_PORT']}
+
        host = config['postgresql']['listen'].split(':')[0]

        config['postgresql']['listen'] = config['postgresql']['connect_address'] = '{0}:{1}'.format(host, self.__PORT)
@@ -531,6 +536,48 @@ class ExhibitorController(ZooKeeperController):
        os.environ.update({'PATRONI_EXHIBITOR_HOSTS': 'localhost', 'PATRONI_EXHIBITOR_PORT': '8181'})


+class RaftController(AbstractDcsController):
+
+    CONTROLLER_ADDR = 'localhost:1234'
+
+    def __init__(self, context):
+        super(RaftController, self).__init__(context)
+        os.environ.update(PATRONI_RAFT_PARTNER_ADDRS="'" + self.CONTROLLER_ADDR + "'", RAFT_PORT='1234')
+        self._raft = None
+
+    def _start(self):
+        env = os.environ.copy()
+        del env['PATRONI_RAFT_PARTNER_ADDRS']
+        env['PATRONI_RAFT_SELF_ADDR'] = self.CONTROLLER_ADDR
+        env['PATRONI_RAFT_DATA_DIR'] = self._work_directory
+        return subprocess.Popen([sys.executable, '-m', 'coverage', 'run',
+                                '--source=patroni', '-p', 'patroni_raft_controller.py'],
+                                stdout=self._log, stderr=subprocess.STDOUT, env=env)
+
+    def query(self, key, scope='batman'):
+        ret = self._raft.get(self.path(key, scope))
+        return ret and ret['value']
+
+    def set(self, key, value):
+        self._raft.set(self.path(key), value)
+
+    def cleanup_service_tree(self):
+        from patroni.dcs.raft import KVStoreTTL
+        from pysyncobj import SyncObjConf
+
+        if self._raft:
+            self._raft.destroy()
+            self._raft._SyncObj__thread.join()
+            self.stop()
+            os.makedirs(self._work_directory)
+            self.start()
+
+        ready_event = threading.Event()
+        conf = SyncObjConf(appendEntriesUseBatch=False, dynamicMembershipChange=True, onReady=ready_event.set)
+        self._raft = KVStoreTTL(None, [self.CONTROLLER_ADDR], conf)
+        ready_event.wait()
+
+
 class PatroniPoolController(object):

    BACKUP_SCRIPT = [sys.executable, 'features/backup_create.py']
--- a/patroni/init.py
+++ b/patroni/init.py
@@ -4,7 +4,8 @@ import signal
 import sys
 import time

-from patroni.version import __version__
+from .daemon import AbstractPatroniDaemon, abstract_main
+from .version import __version__

 logger = logging.getLogger(__name__)

@@ -12,23 +13,19 @@ PATRONI_ENV_PREFIX = 'PATRONI_'
 KUBERNETES_ENV_PREFIX = 'KUBERNETES_'


-class Patroni(object):
+class Patroni(AbstractPatroniDaemon):

-    def __init__(self, conf):
+    def __init__(self, config):
        from patroni.api import RestApiServer
        from patroni.dcs import get_dcs
        from patroni.ha import Ha
-        from patroni.log import PatroniLogger
        from patroni.postgresql import Postgresql
        from patroni.request import PatroniRequest
        from patroni.watchdog import Watchdog

-        self.setup_signal_handlers()
+        super(Patroni, self).__init__(config)

        self.version = __version__
-        self.logger = PatroniLogger()
-        self.config = conf
-        self.logger.reload_config(self.config.get('log', {}))
        self.dcs = get_dcs(self.config)
        self.watchdog = Watchdog(self.config)
        self.load_dynamic_configuration()
@@ -71,14 +68,14 @@ class Patroni(object):
    def nosync(self):
        return bool(self.tags.get('nosync', False))

-    def reload_config(self, sighup=False):
+    def reload_config(self, sighup=False, local=False):
        try:
-            self.tags = self.get_tags()
-            self.logger.reload_config(self.config.get('log', {}))
-            self.watchdog.reload_config(self.config)
-            if sighup:
+            super(Patroni, self).reload_config(sighup, local)
+            if local:
+                self.tags = self.get_tags()
                self.request.reload_config(self.config)
-            self.api.reload_config(self.config['restapi'])
+                self.api.reload_config(self.config['restapi'])
+            self.watchdog.reload_config(self.config)
            self.postgresql.reload_config(self.config['postgresql'], sighup)
            self.dcs.reload_config(self.config)
        except Exception:
@@ -88,15 +85,6 @@ class Patroni(object):
    def replicatefrom(self):
        return self.tags.get('replicatefrom')

-    def sighup_handler(self, *args):
-        self._received_sighup = True
-
-    def sigterm_handler(self, *args):
-        with self._sigterm_lock:
-            if not self._received_sigterm:
-                self._received_sigterm = True
-                sys.exit()
-
    @property
    def noloadbalance(self):
        return bool(self.tags.get('noloadbalance', False))
@@ -114,48 +102,24 @@ class Patroni(object):
        elif self.ha.watch(nap_time):
            self.next_run = time.time()

-    @property
-    def received_sigterm(self):
-        with self._sigterm_lock:
-            return self._received_sigterm
-
    def run(self):
        self.api.start()
-        self.logger.start()
        self.next_run = time.time()
+        super(Patroni, self).run()

-        while not self.received_sigterm:
-            if self._received_sighup:
-                self._received_sighup = False
-                if self.config.reload_local_configuration():
-                    self.reload_config(True)
-                else:
-                    self.postgresql.config.reload_config(self.config['postgresql'], True)
+    def _run_cycle(self):
+        logger.info(self.ha.run_cycle())

-            logger.info(self.ha.run_cycle())
+        if self.dcs.cluster and self.dcs.cluster.config and self.dcs.cluster.config.data \
+                and self.config.set_dynamic_configuration(self.dcs.cluster.config):
+            self.reload_config()

-            if self.dcs.cluster and self.dcs.cluster.config and self.dcs.cluster.config.data \
-                    and self.config.set_dynamic_configuration(self.dcs.cluster.config):
-                self.reload_config()
+        if self.postgresql.role != 'uninitialized':
+            self.config.save_cache()

-            if self.postgresql.role != 'uninitialized':
-                self.config.save_cache()
+        self.schedule_next_run()

-            self.schedule_next_run()
-
-    def setup_signal_handlers(self):
-        from threading import Lock
-
-        self._received_sighup = False
-        self._sigterm_lock = Lock()
-        self._received_sigterm = False
-        if os.name != 'nt':
-            signal.signal(signal.SIGHUP, self.sighup_handler)
-        signal.signal(signal.SIGTERM, self.sigterm_handler)
-
-    def shutdown(self):
-        with self._sigterm_lock:
-            self._received_sigterm = True
+    def _shutdown(self):
        try:
            self.api.shutdown()
        except Exception:
@@ -164,43 +128,14 @@ class Patroni(object):
            self.ha.shutdown()
        except Exception:
            logger.exception('Exception during Ha.shutdown')
-        self.logger.shutdown()


 def patroni_main():
-    import argparse
-
    from multiprocessing import freeze_support
-    from patroni.config import Config, ConfigParseError
    from patroni.validator import schema

    freeze_support()
-
-    parser = argparse.ArgumentParser()
-    parser.add_argument('--version', action='version', version='%(prog)s {0}'.format(__version__))
-    parser.add_argument('--validate-config', action='store_true', help='Run config validator and exit')
-    parser.add_argument('configfile', nargs='?', default='',
-                        help='Patroni may also read the configuration from the {0} environment variable'
-                        .format(Config.PATRONI_CONFIG_VARIABLE))
-    args = parser.parse_args()
-    try:
-        if args.validate_config:
-            conf = Config(args.configfile, validator=schema)
-            sys.exit()
-        else:
-            conf = Config(args.configfile)
-    except ConfigParseError as e:
-        if e.value:
-            print(e.value)
-        parser.print_help()
-        sys.exit(1)
-    patroni = Patroni(conf)
-    try:
-        patroni.run()
-    except KeyboardInterrupt:
-        pass
-    finally:
-        patroni.shutdown()
+    abstract_main(Patroni, schema)


 def fatal(string, *args):
--- a/patroni/config.py
+++ b/patroni/config.py
@@ -293,6 +293,10 @@ class Config(object):
                logger.exception('Exception when parsing list %s', value)
                return None

+        _set_section_values('raft', ['data_dir', 'self_addr', 'partner_addrs'])
+        if 'raft' in ret and 'partner_addrs' in ret['raft']:
+            ret['raft']['partner_addrs'] = _parse_list(ret['raft']['partner_addrs'])
+
        for param in list(os.environ.keys()):
            if param.startswith(PATRONI_ENV_PREFIX):
                # PATRONI_(ETCD|CONSUL|ZOOKEEPER|EXHIBITOR|...)_(HOSTS?|PORT|..)
--- a/patroni/daemon.py
+++ b/patroni/daemon.py
@@ -0,0 +1,104 @@
+import abc
+import os
+import signal
+import six
+import sys
+
+from threading import Lock
+
+
+@six.add_metaclass(abc.ABCMeta)
+class AbstractPatroniDaemon(object):
+
+    def __init__(self, config):
+        from patroni.log import PatroniLogger
+
+        self.setup_signal_handlers()
+
+        self.logger = PatroniLogger()
+        self.config = config
+        AbstractPatroniDaemon.reload_config(self, local=True)
+
+    def sighup_handler(self, *args):
+        self._received_sighup = True
+
+    def sigterm_handler(self, *args):
+        with self._sigterm_lock:
+            if not self._received_sigterm:
+                self._received_sigterm = True
+                sys.exit()
+
+    def setup_signal_handlers(self):
+        self._received_sighup = False
+        self._sigterm_lock = Lock()
+        self._received_sigterm = False
+        if os.name != 'nt':
+            signal.signal(signal.SIGHUP, self.sighup_handler)
+        signal.signal(signal.SIGTERM, self.sigterm_handler)
+
+    @property
+    def received_sigterm(self):
+        with self._sigterm_lock:
+            return self._received_sigterm
+
+    def reload_config(self, sighup=False, local=False):
+        if local:
+            self.logger.reload_config(self.config.get('log', {}))
+
+    @abc.abstractmethod
+    def _run_cycle(self):
+        """_run_cycle"""
+
+    def run(self):
+        self.logger.start()
+        while not self.received_sigterm:
+            if self._received_sighup:
+                self._received_sighup = False
+                self.reload_config(True, self.config.reload_local_configuration())
+
+            self._run_cycle()
+
+    @abc.abstractmethod
+    def _shutdown(self):
+        """_shutdown"""
+
+    def shutdown(self):
+        with self._sigterm_lock:
+            self._received_sigterm = True
+        self._shutdown()
+        self.logger.shutdown()
+
+
+def abstract_main(cls, validator=None):
+    import argparse
+
+    from .config import Config, ConfigParseError
+    from .version import __version__
+
+    parser = argparse.ArgumentParser()
+    parser.add_argument('--version', action='version', version='%(prog)s {0}'.format(__version__))
+    if validator:
+        parser.add_argument('--validate-config', action='store_true', help='Run config validator and exit')
+    parser.add_argument('configfile', nargs='?', default='',
+                        help='Patroni may also read the configuration from the {0} environment variable'
+                        .format(Config.PATRONI_CONFIG_VARIABLE))
+    args = parser.parse_args()
+    try:
+        if validator and args.validate_config:
+            Config(args.configfile, validator=validator)
+            sys.exit()
+
+        config = Config(args.configfile)
+    except ConfigParseError as e:
+        if e.value:
+            print(e.value)
+        parser.print_help()
+        sys.exit(1)
+
+    controller = cls(config)
+    try:
+        controller.run()
+    except KeyboardInterrupt:
+        pass
+    finally:
+        controller.shutdown()
--- a/patroni/dcs/raft.py
+++ b/patroni/dcs/raft.py
@@ -0,0 +1,409 @@
+import json
+import logging
+import os
+import threading
+import time
+
+from patroni.dcs import AbstractDCS, ClusterConfig, Cluster, Failover, Leader, Member, SyncState, TimelineHistory
+from pysyncobj import SyncObj, SyncObjConf, replicated, FAIL_REASON
+from pysyncobj.transport import Node, TCPTransport, CONNECTION_STATE
+
+logger = logging.getLogger(__name__)
+
+
+class MessageNode(Node):
+
+    def __init__(self, address):
+        self.address = address
+
+
+class UtilityTransport(TCPTransport):
+
+    def __init__(self, syncObj, selfNode, otherNodes):
+        super(UtilityTransport, self).__init__(syncObj, selfNode, otherNodes)
+        self._selfIsReadonlyNode = False
+
+    def _connectIfNecessarySingle(self, node):
+        pass
+
+    def connectionState(self, node):
+        return self._connections[node].state
+
+    def isDisconnected(self, node):
+        return self.connectionState(node) == CONNECTION_STATE.DISCONNECTED
+
+    def connectIfRequiredSingle(self, node):
+        if self.isDisconnected(node):
+            return self._connections[node].connect(node.ip, node.port)
+
+    def disconnectSingle(self, node):
+        self._connections[node].disconnect()
+
+
+class SyncObjUtility(SyncObj):
+
+    def __init__(self, otherNodes, conf):
+        autoTick = conf.autoTick
+        conf.autoTick = False
+        super(SyncObjUtility, self).__init__(None, otherNodes, conf, transportClass=UtilityTransport)
+        conf.autoTick = autoTick
+        self._SyncObj__transport.setOnMessageReceivedCallback(self._onMessageReceived)
+        self.__result = None
+
+    def setPartnerNode(self, partner):
+        self.__node = partner
+
+    def sendMessage(self, message):
+        # Abuse the fact that node address is send as a first message
+        self._SyncObj__transport._selfNode = MessageNode(message)
+        self._SyncObj__transport.connectIfRequiredSingle(self.__node)
+        while not self._SyncObj__transport.isDisconnected(self.__node):
+            self._poller.poll(0.5)
+        return self.__result
+
+    def _onMessageReceived(self, _, message):
+        self.__result = message
+        self._SyncObj__transport.disconnectSingle(self.__node)
+
+
+class MyTCPTransport(TCPTransport):
+
+    def _onIncomingMessageReceived(self, conn, message):
+        if self._syncObj.encryptor and not conn.sendRandKey:
+            conn.sendRandKey = message
+            conn.recvRandKey = os.urandom(32)
+            conn.send(conn.recvRandKey)
+            return
+
+        # Utility messages
+        if isinstance(message, list) and message[0] == 'members':
+            conn.send(self._syncObj._get_members())
+            return True
+
+        return super(MyTCPTransport, self)._onIncomingMessageReceived(conn, message)
+
+
+class DynMemberSyncObj(SyncObj):
+
+    def __init__(self, selfAddress, partnerAddrs, conf):
+        add_self = False
+        if selfAddress:
+            utility = SyncObjUtility(partnerAddrs, conf)
+            for node in utility._SyncObj__otherNodes:
+                utility.setPartnerNode(node)
+                response = utility.sendMessage(['members'])
+                if response:
+                    partnerAddrs = [member['addr'] for member in response if member['addr'] != selfAddress]
+                    add_self = len(partnerAddrs) == len(response)
+                    break
+
+        super(DynMemberSyncObj, self).__init__(selfAddress, partnerAddrs, conf, transportClass=MyTCPTransport)
+        if add_self:
+            threading.Thread(target=utility.sendMessage, args=(['add', selfAddress],)).start()
+
+    def _get_members(self):
+        ret = [{'addr': node.id, 'leader': node == self._getLeader(),
+                'status': CONNECTION_STATE.CONNECTED if node in self._SyncObj__connectedNodes
+                else CONNECTION_STATE.DISCONNECTED} for node in self._SyncObj__otherNodes]
+        ret.append({'addr': self._SyncObj__selfNode.id, 'leader': self._isLeader(),
+                    'status': CONNECTION_STATE.CONNECTED})
+        return ret
+
+    def _SyncObj__doChangeCluster(self, request, reverse=False):
+        ret = False
+        if not self._SyncObj__selfNode or request[0] != 'add' or reverse or request[1] != self._SyncObj__selfNode.id:
+            ret = super(DynMemberSyncObj, self)._SyncObj__doChangeCluster(request, reverse)
+            if ret:
+                self.forceLogCompaction()
+        return ret
+
+
+class KVStoreTTL(DynMemberSyncObj):
+
+    def __init__(self, selfAddress, partnerAddrs, conf, on_set=None, on_delete=None):
+        self.__on_set = on_set
+        self.__on_delete = on_delete
+        self.__limb = {}
+        self.__retry_timeout = None
+        self.__early_apply_local_log = selfAddress is not None
+        self.applied_local_log = False
+        super(KVStoreTTL, self).__init__(selfAddress, partnerAddrs, conf)
+        self.__data = {}
+
+    @staticmethod
+    def __check_requirements(old_value, **kwargs):
+        return ('prevExist' not in kwargs or bool(kwargs['prevExist']) == bool(old_value)) and \
+            ('prevValue' not in kwargs or old_value and old_value['value'] == kwargs['prevValue']) and \
+            (not kwargs.get('prevIndex') or old_value and old_value['index'] == kwargs['prevIndex'])
+
+    def set_retry_timeout(self, retry_timeout):
+        self.__retry_timeout = retry_timeout
+
+    def retry(self, func, *args, **kwargs):
+        event = threading.Event()
+        ret = {'result': None, 'error': -1}
+
+        def callback(result, error):
+            ret.update(result=result, error=error)
+            event.set()
+
+        kwargs['callback'] = callback
+        timeout = kwargs.pop('timeout', None) or self.__retry_timeout
+        deadline = timeout and time.time() + timeout
+
+        while True:
+            event.clear()
+            func(*args, **kwargs)
+            event.wait(timeout)
+            if ret['error'] == FAIL_REASON.SUCCESS:
+                return ret['result']
+            elif ret['error'] == FAIL_REASON.REQUEST_DENIED:
+                break
+            elif deadline:
+                timeout = deadline - time.time()
+                if timeout <= 0:
+                    break
+            time.sleep(1)
+        return False
+
+    @replicated
+    def _set(self, key, value, **kwargs):
+        old_value = self.__data.get(key, {})
+        if not self.__check_requirements(old_value, **kwargs):
+            return False
+
+        if old_value and old_value['created'] != value['created']:
+            value['created'] = value['updated']
+        value['index'] = self._SyncObj__raftLastApplied + 1
+
+        self.__data[key] = value
+        if self.__on_set:
+            self.__on_set(key, value)
+        return True
+
+    def set(self, key, value, ttl=None, **kwargs):
+        old_value = self.__data.get(key, {})
+        if not self.__check_requirements(old_value, **kwargs):
+            return False
+
+        value = {'value': value, 'updated': time.time()}
+        value['created'] = old_value.get('created', value['updated'])
+        if ttl:
+            value['expire'] = value['updated'] + ttl
+        return self.retry(self._set, key, value, **kwargs)
+
+    def __pop(self, key):
+        self.__data.pop(key)
+        if self.__on_delete:
+            self.__on_delete(key)
+
+    @replicated
+    def _delete(self, key, recursive=False, **kwargs):
+        if recursive:
+            for k in list(self.__data.keys()):
+                if k.startswith(key):
+                    self.__pop(k)
+        elif not self.__check_requirements(self.__data.get(key, {}), **kwargs):
+            return False
+        else:
+            self.__pop(key)
+        return True
+
+    def delete(self, key, recursive=False, **kwargs):
+        if not recursive and not self.__check_requirements(self.__data.get(key, {}), **kwargs):
+            return False
+        return self.retry(self._delete, key, recursive=recursive, **kwargs)
+
+    @staticmethod
+    def __values_match(old, new):
+        return all(old.get(n) == new.get(n) for n in ('created', 'updated', 'expire', 'value'))
+
+    @replicated
+    def _expire(self, key, value, callback=None):
+        current = self.__data.get(key)
+        if current and self.__values_match(current, value):
+            self.__pop(key)
+
+    def __expire_keys(self):
+        for key, value in self.__data.items():
+            if value and 'expire' in value and value['expire'] <= time.time() and \
+                    not (key in self.__limb and self.__values_match(self.__limb[key], value)):
+                self.__limb[key] = value
+
+                def callback(*args):
+                    if key in self.__limb and self.__values_match(self.__limb[key], value):
+                        self.__limb.pop(key)
+                self._expire(key, value, callback=callback)
+
+    def get(self, key, recursive=False):
+        if not recursive:
+            return self.__data.get(key)
+        return {k: v for k, v in self.__data.items() if k.startswith(key)}
+
+    def _onTick(self, timeToWait=0.0):
+        # The SyncObj starts applying the local log only when there is at least one node connected.
+        # We want to change this behavior and apply the local log even when there is nobody except us.
+        # It gives us at least some picture about the last known cluster state.
+        if self.__early_apply_local_log and not self.applied_local_log and self._SyncObj__needLoadDumpFile:
+            self._SyncObj__raftCommitIndex = self._SyncObj__getCurrentLogIndex()
+            self._SyncObj__raftCurrentTerm = self._SyncObj__getCurrentLogTerm()
+
+        super(KVStoreTTL, self)._onTick(timeToWait)
+
+        # The SyncObj calls onReady callback only when cluster got the leader and is ready for writes.
+        # In some cases for us it is safe to "signal" the Raft object when the local log is fully applied.
+        # We are using the `applied_local_log` property for that, but not calling the callback function.
+        if self.__early_apply_local_log and not self.applied_local_log and self._SyncObj__raftCommitIndex != 1 and \
+                self._SyncObj__raftLastApplied == self._SyncObj__raftCommitIndex:
+            self.applied_local_log = True
+
+        if self._isLeader():
+            self.__expire_keys()
+        else:
+            self.__limb.clear()
+
+
+class Raft(AbstractDCS):
+
+    def __init__(self, config):
+        super(Raft, self).__init__(config)
+        self._ttl = int(config.get('ttl') or 30)
+
+        self_addr = None if self._ctl else config.get('self_addr')
+        template = os.path.join(config.get('data_dir', ''), self_addr or '')
+        files = {'journalFile': template + '.journal', 'fullDumpFile': template + '.dump'} if self_addr else {}
+
+        ready_event = threading.Event()
+        conf = SyncObjConf(commandsWaitLeader=False, appendEntriesUseBatch=False, onReady=ready_event.set,
+                           dynamicMembershipChange=True, **files)
+        self._sync_obj = KVStoreTTL(self_addr, config.get('partner_addrs', []), conf, self._on_set, self._on_delete)
+        while True:
+            ready_event.wait(5)
+            if ready_event.isSet() or self._sync_obj.applied_local_log:
+                break
+            else:
+                logger.info('waiting on raft')
+        self._sync_obj.forceLogCompaction()
+        self.set_retry_timeout(int(config.get('retry_timeout') or 10))
+
+    def _on_set(self, key, value):
+        leader = (self._sync_obj.get(self.leader_path) or {}).get('value')
+        if key == value['created'] == value['updated'] and \
+                (key.startswith(self.members_path) or key == self.leader_path and leader != self._name) or \
+                key == self.leader_optime_path and leader != self._name or key in (self.config_path, self.sync_path):
+            self.event.set()
+
+    def _on_delete(self, key):
+        if key == self.leader_path:
+            self.event.set()
+
+    def set_ttl(self, ttl):
+        self._ttl = ttl
+
+    @property
+    def ttl(self):
+        return self._ttl
+
+    def set_retry_timeout(self, retry_timeout):
+        self._sync_obj.set_retry_timeout(retry_timeout)
+
+    @staticmethod
+    def member(key, value):
+        return Member.from_node(value['index'], os.path.basename(key), None, value['value'])
+
+    def _load_cluster(self):
+        prefix = self.client_path('')
+        response = self._sync_obj.get(prefix, recursive=True)
+        if not response:
+            return Cluster(None, None, None, None, [], None, None, None)
+        nodes = {os.path.relpath(key, prefix).replace('\\', '/'): value for key, value in response.items()}
+
+        # get initialize flag
+        initialize = nodes.get(self._INITIALIZE)
+        initialize = initialize and initialize['value']
+
+        # get global dynamic configuration
+        config = nodes.get(self._CONFIG)
+        config = config and ClusterConfig.from_node(config['index'], config['value'])
+
+        # get timeline history
+        history = nodes.get(self._HISTORY)
+        history = history and TimelineHistory.from_node(history['index'], history['value'])
+
+        # get last leader operation
+        last_leader_operation = nodes.get(self._LEADER_OPTIME)
+        last_leader_operation = 0 if last_leader_operation is None else int(last_leader_operation['value'])
+
+        # get list of members
+        members = [self.member(k, n) for k, n in nodes.items() if k.startswith(self._MEMBERS) and k.count('/') == 1]
+
+        # get leader
+        leader = nodes.get(self._LEADER)
+        if leader:
+            member = Member(-1, leader['value'], None, {})
+            member = ([m for m in members if m.name == leader['value']] or [member])[0]
+            leader = Leader(leader['index'], None, member)
+
+        # failover key
+        failover = nodes.get(self._FAILOVER)
+        if failover:
+            failover = Failover.from_node(failover['index'], failover['value'])
+
+        # get synchronization state
+        sync = nodes.get(self._SYNC)
+        sync = SyncState.from_node(sync and sync['index'], sync and sync['value'])
+
+        return Cluster(initialize, config, leader, last_leader_operation, members, failover, sync, history)
+
+    def _write_leader_optime(self, last_operation):
+        return self._sync_obj.set(self.leader_optime_path, last_operation, timeout=1)
+
+    def _update_leader(self):
+        ret = self._sync_obj.set(self.leader_path, self._name, ttl=self._ttl, prevValue=self._name)
+        if not ret and self._sync_obj.get(self.leader_path) is None:
+            ret = self.attempt_to_acquire_leader()
+        return ret
+
+    def attempt_to_acquire_leader(self, permanent=False):
+        return self._sync_obj.set(self.leader_path, self._name, prevExist=False,
+                                  ttl=None if permanent else self._ttl)
+
+    def set_failover_value(self, value, index=None):
+        return self._sync_obj.set(self.failover_path, value, prevIndex=index)
+
+    def set_config_value(self, value, index=None):
+        return self._sync_obj.set(self.config_path, value, prevIndex=index)
+
+    def touch_member(self, data, permanent=False):
+        data = json.dumps(data, separators=(',', ':'))
+        return self._sync_obj.set(self.member_path, data, None if permanent else self._ttl, timeout=2)
+
+    def take_leader(self):
+        return self._sync_obj.set(self.leader_path, self._name, ttl=self._ttl)
+
+    def initialize(self, create_new=True, sysid=''):
+        return self._sync_obj.set(self.initialize_path, sysid, prevExist=(not create_new))
+
+    def _delete_leader(self):
+        return self._sync_obj.delete(self.leader_path, prevValue=self._name, timeout=1)
+
+    def cancel_initialization(self):
+        return self._sync_obj.delete(self.initialize_path)
+
+    def delete_cluster(self):
+        return self._sync_obj.delete(self.client_path(''), recursive=True)
+
+    def set_history_value(self, value):
+        return self._sync_obj.set(self.history_path, value)
+
+    def set_sync_state_value(self, value, index=None):
+        return self._sync_obj.set(self.sync_path, value, prevIndex=index)
+
+    def delete_sync_state(self, index=None):
+        return self._sync_obj.delete(self.sync_path, prevIndex=index)
+
+    def watch(self, leader_index, timeout):
+        try:
+            return super(Raft, self).watch(leader_index, timeout)
+        finally:
+            self.event.clear()
--- a/patroni/raft_controller.py
+++ b/patroni/raft_controller.py
@@ -0,0 +1,34 @@
+import logging
+import os
+
+from patroni.daemon import AbstractPatroniDaemon, abstract_main
+from patroni.dcs.raft import KVStoreTTL
+from pysyncobj import SyncObjConf
+
+logger = logging.getLogger(__name__)
+
+
+class RaftController(AbstractPatroniDaemon):
+
+    def __init__(self, config):
+        super(RaftController, self).__init__(config)
+
+        raft_config = self.config.get('raft')
+        self_addr = raft_config['self_addr']
+        template = os.path.join(raft_config.get('data_dir', ''), self_addr)
+        self._syncobj_config = SyncObjConf(autoTick=False, appendEntriesUseBatch=False, dynamicMembershipChange=True,
+                                           journalFile=template + '.journal', fullDumpFile=template + '.dump')
+        self._raft = KVStoreTTL(self_addr, raft_config.get('partner_addrs', []), self._syncobj_config)
+
+    def _run_cycle(self):
+        try:
+            self._raft.doTick(self._syncobj_config.autoTickPeriod)
+        except Exception:
+            logger.exception('doTick')
+
+    def _shutdown(self):
+        self._raft.destroy()
+
+
+def main():
+    abstract_main(RaftController)
--- a/patroni_raft_controller.py
+++ b/patroni_raft_controller.py
@@ -0,0 +1,6 @@
+#!/usr/bin/env python
+from patroni.raft_controller import main
+
+
+if __name__ == '__main__':
+    main()
--- a/postgres0.yml
+++ b/postgres0.yml
@@ -30,6 +30,13 @@ etcd:
  #It is possible to change this behavior through by setting:
  #use_proxies: true

+#raft:
+#  data_dir: .
+#  self_addr: 127.0.0.1:2222
+#  partner_addrs:
+#  - 127.0.0.1:2223
+#  - 127.0.0.1:2224
+
 bootstrap:
  # this section will be written into Etcd:/<namespace>/<scope>/config after initializing new cluster
  # and all other cluster members will use it as a `global configuration`
--- a/postgres1.yml
+++ b/postgres1.yml
@@ -30,6 +30,13 @@ etcd:
  #It is possible to change this behavior through by setting:
  #use_proxies: true

+#raft:
+#  data_dir: .
+#  self_addr: 127.0.0.1:2223
+#  partner_addrs:
+#  - 127.0.0.1:2222
+#  - 127.0.0.1:2224
+
 bootstrap:
  # this section will be written into Etcd:/<namespace>/<scope>/config after initializing new cluster
  # and all other cluster members will use it as a `global configuration`
--- a/postgres2.yml
+++ b/postgres2.yml
@@ -30,6 +30,13 @@ etcd:
  #It is possible to change this behavior through by setting:
  #use_proxies: true

+#raft:
+#  data_dir: .
+#  self_addr: 127.0.0.1:2224
+#  partner_addrs:
+#  - 127.0.0.1:2222
+#  - 127.0.0.1:2223
+
 bootstrap:
  # this section will be written into Etcd:/<namespace>/<scope>/config after initializing new cluster
  # and all other cluster members will use it as a `global configuration`
--- a/requirements.txt
+++ b/requirements.txt
@@ -8,5 +8,6 @@ python-consul>=0.7.1
 click>=4.1
 prettytable>=0.7
 python-dateutil
+pysyncobj>=0.3.5
 psutil>=2.0.0
 cdiff
--- a/setup.py
+++ b/setup.py
@@ -23,7 +23,7 @@ KEYWORDS = 'etcd governor patroni postgresql postgres ha haproxy confd' +\
    ' zookeeper exhibitor consul streaming replication kubernetes k8s'

 EXTRAS_REQUIRE = {'aws': ['boto'], 'etcd': ['python-etcd'], 'consul': ['python-consul'],
-                  'exhibitor': ['kazoo'], 'zookeeper': ['kazoo'], 'kubernetes': []}
+                  'exhibitor': ['kazoo'], 'zookeeper': ['kazoo'], 'kubernetes': [], 'raft': ['pysyncobj']}
 COVERAGE_XML = True
 COVERAGE_HTML = False

@@ -51,6 +51,7 @@ CLASSIFIERS = [

 CONSOLE_SCRIPTS = ['patroni = patroni:main',
                   'patronictl = patroni.ctl:ctl',
+                   'patroni_raft_controller = patroni.raft_controller:main',
                   "patroni_wale_restore = patroni.scripts.wale_restore:main",
                   "patroni_aws = patroni.scripts.aws:main"]

--- a/tests/test_config.py
+++ b/tests/test_config.py
@@ -55,6 +55,7 @@ class TestConfig(unittest.TestCase):
            'PATRONI_ZOOKEEPER_HOSTS': "'host1:2181','host2:2181'",
            'PATRONI_EXHIBITOR_HOSTS': 'host1,host2',
            'PATRONI_EXHIBITOR_PORT': '8181',
+            'PATRONI_RAFT_PARTNER_ADDRS': "'host1:1234','host2:1234'",
            'PATRONI_foo_HOSTS': '[host1,host2',  # Exception in parse_list
            'PATRONI_SUPERUSER_USERNAME': 'postgres',
            'PATRONI_SUPERUSER_PASSWORD': 'zalando',
--- a/tests/test_patroni.py
+++ b/tests/test_patroni.py
@@ -167,7 +167,7 @@ class TestPatroni(unittest.TestCase):
    def test_reload_config(self):
        self.p.reload_config()
        self.p.get_tags = Mock(side_effect=Exception)
-        self.p.reload_config()
+        self.p.reload_config(local=True)

    def test_nosync(self):
        self.p.tags['nosync'] = True
--- a/tests/test_raft.py
+++ b/tests/test_raft.py
@@ -0,0 +1,144 @@
+import os
+import unittest
+import time
+
+from mock import Mock, patch
+from patroni.dcs.raft import DynMemberSyncObj, KVStoreTTL, Raft, SyncObjUtility
+from pysyncobj import SyncObjConf, FAIL_REASON
+
+
+@patch('pysyncobj.tcp_server.TcpServer.bind', Mock())
+class TestDynMemberSyncObj(unittest.TestCase):
+
+    @patch('pysyncobj.tcp_server.TcpServer.bind', Mock())
+    def setUp(self):
+        self.conf = SyncObjConf(appendEntriesUseBatch=False, dynamicMembershipChange=True, autoTick=False)
+        self.so = DynMemberSyncObj('127.0.0.1:1234', ['127.0.0.1:1235'], self.conf)
+
+    @patch.object(SyncObjUtility, 'sendMessage')
+    def test_add_member(self, mock_send_message):
+        mock_send_message.return_value = [{'addr': '127.0.0.1:1235'}, {'addr': '127.0.0.1:1236'}]
+        mock_send_message.ver = 0
+        DynMemberSyncObj('127.0.0.1:1234', ['127.0.0.1:1235'], self.conf)
+        self.conf.dynamicMembershipChange = False
+        DynMemberSyncObj('127.0.0.1:1234', ['127.0.0.1:1235'], self.conf)
+
+    def test___onUtilityMessage(self):
+        self.so._SyncObj__encryptor = Mock()
+        mock_conn = Mock()
+        mock_conn.sendRandKey = None
+        self.so._SyncObj__transport._onIncomingMessageReceived(mock_conn, 'randkey')
+        self.so._SyncObj__transport._onIncomingMessageReceived(mock_conn, ['members'])
+        self.so._SyncObj__transport._onIncomingMessageReceived(mock_conn, ['status'])
+
+    def test__SyncObj__doChangeCluster(self):
+        self.so._SyncObj__doChangeCluster(['add', '127.0.0.1:1236'])
+
+    def test_utility(self):
+        utility = SyncObjUtility(['127.0.0.1:1235'], self.conf)
+        utility.setPartnerNode(list(utility._SyncObj__otherNodes)[0])
+        utility.sendMessage(['members'])
+        utility._onMessageReceived(0, '')
+
+
+class TestKVStoreTTL(unittest.TestCase):
+
+    def setUp(self):
+        self.conf = SyncObjConf(appendEntriesUseBatch=False, appendEntriesPeriod=0.001, journalFile='foo.journal',
+                                raftMinTimeout=0.004, raftMaxTimeout=0.005, autoTickPeriod=0.001)
+        callback = Mock()
+        callback.replicated = False
+        self.so = KVStoreTTL('127.0.0.1:1234', [], self.conf, on_set=callback, on_delete=callback)
+        self.so.set_retry_timeout(10)
+
+    @staticmethod
+    def destroy(so):
+        so.destroy()
+        so._SyncObj__thread.join()
+
+    def tearDown(self):
+        if self.so:
+            self.destroy(self.so)
+        if os.path.exists('foo.journal'):
+            os.unlink('foo.journal')
+
+    def test_set(self):
+        self.assertTrue(self.so.set('foo', 'bar', prevExist=False, ttl=30))
+        self.assertFalse(self.so.set('foo', 'bar', prevExist=False, ttl=30))
+        self.assertFalse(self.so.retry(self.so._set, 'foo', {'value': 'buz', 'created': 1, 'updated': 1}, prevValue=''))
+        self.assertTrue(self.so.retry(self.so._set, 'foo', {'value': 'buz', 'created': 1, 'updated': 1}))
+
+    def test_delete(self):
+        self.so.set('foo', 'bar')
+        self.so.set('fooo', 'bar')
+        self.assertFalse(self.so.delete('foo', prevValue='buz'))
+        self.assertFalse(self.so.delete('foo', prevValue='bar', timeout=0.00001))
+        self.assertFalse(self.so.delete('foo', prevValue='bar'))
+        self.assertTrue(self.so.delete('foo', recursive=True))
+        self.assertFalse(self.so.retry(self.so._delete, 'foo', prevValue=''))
+
+    def test_expire(self):
+        self.so.set('foo', 'bar', ttl=0.001)
+        time.sleep(1)
+        self.assertIsNone(self.so.get('foo'))
+        self.assertEqual(self.so.get('foo', recursive=True), {})
+
+    @patch('time.sleep', Mock())
+    def test_retry(self):
+        return_values = [FAIL_REASON.QUEUE_FULL, FAIL_REASON.SUCCESS, FAIL_REASON.REQUEST_DENIED]
+
+        def test(callback):
+            callback(True, return_values.pop(0))
+        self.assertTrue(self.so.retry(test))
+        self.assertFalse(self.so.retry(test))
+
+    def test_on_ready_override(self):
+        self.assertTrue(self.so.set('foo', 'bar'))
+        self.destroy(self.so)
+        self.so = None
+        self.conf.onReady = Mock()
+        self.conf.autoTick = False
+        so = KVStoreTTL('127.0.0.1:1234', ['127.0.0.1:1235'], self.conf)
+        so.doTick(0)
+        so.destroy()
+
+
+class TestRaft(unittest.TestCase):
+
+    def test_raft(self):
+        raft = Raft({'ttl': 30, 'scope': 'test', 'name': 'pg', 'self_addr': '127.0.0.1:1234', 'retry_timeout': 10})
+        raft.set_retry_timeout(20)
+        raft.set_ttl(60)
+        self.assertTrue(raft.touch_member(''))
+        self.assertTrue(raft.initialize())
+        self.assertTrue(raft.cancel_initialization())
+        self.assertTrue(raft.set_config_value('{}'))
+        self.assertTrue(raft.write_sync_state('foo', 'bar'))
+        self.assertTrue(raft.update_leader('1'))
+        self.assertTrue(raft.manual_failover('foo', 'bar'))
+        raft.get_cluster()
+        self.assertTrue(raft.delete_sync_state())
+        self.assertTrue(raft.delete_leader())
+        self.assertTrue(raft.set_history_value(''))
+        self.assertTrue(raft.delete_cluster())
+        raft.get_cluster()
+        self.assertTrue(raft.take_leader())
+        raft.watch(None, 0.001)
+        raft._sync_obj.destroy()
+        raft._sync_obj._SyncObj__thread.join()
+
+    def tearDown(self):
+        for f in ('journal', 'dump'):
+            f = '127.0.0.1:1234.' + f
+            if os.path.exists(f):
+                os.unlink(f)
+
+    def setUp(self):
+        self.tearDown()
+
+    @patch('patroni.dcs.raft.KVStoreTTL')
+    @patch('threading.Event')
+    def test_init(self, mock_event, mock_kvstore):
+        mock_kvstore.return_value.applied_local_log = False
+        mock_event.return_value.isSet.side_effect = [False, True]
+        self.assertIsNotNone(Raft({'ttl': 30, 'scope': 'test', 'name': 'pg', 'patronictl': True}))
--- a/tests/test_raft_controller.py
+++ b/tests/test_raft_controller.py
@@ -0,0 +1,46 @@
+import logging
+import os
+import unittest
+
+from mock import Mock, patch
+from pysyncobj import SyncObj
+from patroni.config import Config
+from patroni.raft_controller import RaftController, main as _main
+
+from . import SleepException
+
+
+class TestPatroniRaftController(unittest.TestCase):
+
+    SELF_ADDR = '127.0.0.1:5360'
+
+    def remove_files(self):
+        for f in ('journal', 'dump'):
+            f = self.SELF_ADDR + '.' + f
+            if os.path.exists(f):
+                os.unlink(f)
+
+    @patch('pysyncobj.tcp_server.TcpServer.bind', Mock())
+    def setUp(self):
+        self._handlers = logging.getLogger().handlers[:]
+        self.remove_files()
+        os.environ['PATRONI_RAFT_SELF_ADDR'] = self.SELF_ADDR
+        config = Config('postgres0.yml', validator=None)
+        self.rc = RaftController(config)
+
+    def tearDown(self):
+        logging.getLogger().handlers[:] = self._handlers
+        self.remove_files()
+
+    def test_reload_config(self):
+        self.rc.reload_config()
+
+    @patch('logging.Logger.error', Mock(side_effect=SleepException))
+    @patch.object(SyncObj, 'doTick', Mock(side_effect=Exception))
+    def test_run(self):
+        self.assertRaises(SleepException, self.rc.run)
+        self.rc.shutdown()
+
+    @patch('sys.argv', ['patroni'])
+    def test_patroni_raft_controller_main(self):
+        self.assertRaises(SystemExit, _main)