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raft.py
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raft.py
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import json
import logging
import os
import threading
import time
from collections import defaultdict
from pysyncobj import SyncObj, SyncObjConf, replicated, FAIL_REASON
from pysyncobj.dns_resolver import globalDnsResolver
from pysyncobj.node import TCPNode
from pysyncobj.transport import TCPTransport, CONNECTION_STATE
from pysyncobj.utility import TcpUtility
from typing import Any, Callable, Collection, Dict, List, Optional, Set, Union, TYPE_CHECKING
from . import AbstractDCS, ClusterConfig, Cluster, Failover, Leader, Member, Status, SyncState, TimelineHistory
from ..exceptions import DCSError
from ..postgresql.mpp import AbstractMPP
from ..utils import validate_directory
if TYPE_CHECKING: # pragma: no cover
from ..config import Config
logger = logging.getLogger(__name__)
class RaftError(DCSError):
pass
class _TCPTransport(TCPTransport):
def __init__(self, syncObj: 'DynMemberSyncObj', selfNode: Optional[TCPNode],
otherNodes: Collection[TCPNode]) -> None:
super(_TCPTransport, self).__init__(syncObj, selfNode, otherNodes)
self.setOnUtilityMessageCallback('members', syncObj.getMembers)
def _connectIfNecessarySingle(self, node: TCPNode) -> bool:
try:
return super(_TCPTransport, self)._connectIfNecessarySingle(node)
except Exception as e:
logger.debug('Connection to %s failed: %r', node, e)
return False
def resolve_host(self: TCPNode) -> Optional[str]:
return globalDnsResolver().resolve(self.host)
setattr(TCPNode, 'ip', property(resolve_host))
class SyncObjUtility(object):
def __init__(self, otherNodes: Collection[Union[str, TCPNode]], conf: SyncObjConf, retry_timeout: int = 10) -> None:
self._nodes = otherNodes
self._utility = TcpUtility(conf.password, retry_timeout / max(1, len(otherNodes)))
self.__node = next(iter(otherNodes), None)
def executeCommand(self, command: List[Any]) -> Any:
try:
if self.__node:
return self._utility.executeCommand(self.__node, command)
except Exception:
return None
def getMembers(self) -> Optional[List[str]]:
for self.__node in self._nodes:
response = self.executeCommand(['members'])
if response:
return [member['addr'] for member in response]
class DynMemberSyncObj(SyncObj):
def __init__(self, selfAddress: Optional[str], partnerAddrs: Collection[str],
conf: SyncObjConf, retry_timeout: int = 10) -> None:
self.__early_apply_local_log = selfAddress is not None
self.applied_local_log = False
utility = SyncObjUtility(partnerAddrs, conf, retry_timeout)
members = utility.getMembers()
add_self = members and selfAddress not in members
partnerAddrs = [member for member in (members or partnerAddrs) if member != selfAddress]
super(DynMemberSyncObj, self).__init__(selfAddress, partnerAddrs, conf, transportClass=_TCPTransport)
if add_self:
thread = threading.Thread(target=utility.executeCommand, args=(['add', selfAddress],))
thread.daemon = True
thread.start()
def getMembers(self, args: Any, callback: Callable[[Any, Any], Any]) -> None:
callback([{'addr': node.id, 'leader': node == self._getLeader(), 'status': CONNECTION_STATE.CONNECTED
if self.isNodeConnected(node) else CONNECTION_STATE.DISCONNECTED} for node in self.otherNodes]
+ [{'addr': self.selfNode.id, 'leader': self._isLeader(), 'status': CONNECTION_STATE.CONNECTED}], None)
def _onTick(self, timeToWait: float = 0.0):
super(DynMemberSyncObj, 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.raftLastApplied == self.raftCommitIndex:
self.applied_local_log = True
class KVStoreTTL(DynMemberSyncObj):
def __init__(self, on_ready: Optional[Callable[..., Any]], on_set: Optional[Callable[[str, Dict[str, Any]], None]],
on_delete: Optional[Callable[[str], None]], **config: Any) -> None:
self.__thread = None
self.__on_set = on_set
self.__on_delete = on_delete
self.__limb: Dict[str, Dict[str, Any]] = {}
self.set_retry_timeout(int(config.get('retry_timeout') or 10))
self_addr = config.get('self_addr')
partner_addrs: Set[str] = set(config.get('partner_addrs', []))
if config.get('patronictl'):
if self_addr:
partner_addrs.add(self_addr)
self_addr = None
# Create raft data_dir if necessary
raft_data_dir = config.get('data_dir', '')
if raft_data_dir != '':
validate_directory(raft_data_dir)
file_template = (self_addr or '')
file_template = file_template.replace(':', '_') if os.name == 'nt' else file_template
file_template = os.path.join(raft_data_dir, file_template)
conf = SyncObjConf(password=config.get('password'), autoTick=False, appendEntriesUseBatch=False,
bindAddress=config.get('bind_addr'), dnsFailCacheTime=(config.get('loop_wait') or 10),
dnsCacheTime=(config.get('ttl') or 30), commandsWaitLeader=config.get('commandsWaitLeader'),
fullDumpFile=(file_template + '.dump' if self_addr else None),
journalFile=(file_template + '.journal' if self_addr else None),
onReady=on_ready, dynamicMembershipChange=True)
super(KVStoreTTL, self).__init__(self_addr, partner_addrs, conf, self.__retry_timeout)
self.__data: Dict[str, Dict[str, Any]] = {}
@staticmethod
def __check_requirements(old_value: Dict[str, Any], **kwargs: Any) -> bool:
return bool(('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 (kwargs.get('prevIndex') is None or old_value and old_value['index'] == kwargs['prevIndex']))
def set_retry_timeout(self, retry_timeout: int) -> None:
self.__retry_timeout = retry_timeout
def retry(self, func: Callable[..., Any], *args: Any, **kwargs: Any) -> Any:
event = threading.Event()
ret = {'result': None, 'error': -1}
def callback(result: Any, error: Any) -> None:
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:
raise RaftError('timeout')
time.sleep(1)
return False
@replicated
def _set(self, key: str, value: Dict[str, Any], **kwargs: Any) -> Union[bool, Dict[str, Any]]:
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.raftLastApplied + 1
self.__data[key] = value
if self.__on_set:
self.__on_set(key, value)
return value
def set(self, key: str, value: str, ttl: Optional[int] = None,
handle_raft_error: bool = True, **kwargs: Any) -> Union[bool, Dict[str, Any]]:
old_value = self.__data.get(key, {})
if not self.__check_requirements(old_value, **kwargs):
return False
data: Dict[str, Any] = {'value': value, 'updated': time.time()}
data['created'] = old_value.get('created', data['updated'])
if ttl:
data['expire'] = data['updated'] + ttl
try:
return self.retry(self._set, key, data, **kwargs)
except RaftError:
if not handle_raft_error:
raise
return False
def __pop(self, key: str) -> None:
self.__data.pop(key)
if self.__on_delete:
self.__on_delete(key)
@replicated
def _delete(self, key: str, recursive: bool = False, **kwargs: Any) -> bool:
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: str, recursive: bool = False, **kwargs: Any) -> bool:
if not recursive and not self.__check_requirements(self.__data.get(key, {}), **kwargs):
return False
try:
return self.retry(self._delete, key, recursive=recursive, **kwargs)
except RaftError:
return False
@staticmethod
def __values_match(old: Dict[str, Any], new: Dict[str, Any]) -> bool:
return all(old.get(n) == new.get(n) for n in ('created', 'updated', 'expire', 'value'))
@replicated
def _expire(self, key: str, value: Dict[str, Any], callback: Optional[Callable[..., Any]] = None) -> None:
current = self.__data.get(key)
if current and self.__values_match(current, value):
self.__pop(key)
def __expire_keys(self) -> None:
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: Any) -> None:
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: str, recursive: bool = False) -> Union[None, Dict[str, Any], Dict[str, Dict[str, Any]]]:
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: float = 0.0) -> None:
super(KVStoreTTL, self)._onTick(timeToWait)
if self._isLeader():
self.__expire_keys()
else:
self.__limb.clear()
def _autoTickThread(self) -> None:
self.__destroying = False
while not self.__destroying:
self.doTick(self.conf.autoTickPeriod)
def startAutoTick(self) -> None:
self.__thread = threading.Thread(target=self._autoTickThread)
self.__thread.daemon = True
self.__thread.start()
def destroy(self) -> None:
if self.__thread:
self.__destroying = True
self.__thread.join()
super(KVStoreTTL, self).destroy()
class Raft(AbstractDCS):
def __init__(self, config: Dict[str, Any], mpp: AbstractMPP) -> None:
super(Raft, self).__init__(config, mpp)
self._ttl = int(config.get('ttl') or 30)
ready_event = threading.Event()
self._sync_obj = KVStoreTTL(ready_event.set, self._on_set, self._on_delete, commandsWaitLeader=False, **config)
self._sync_obj.startAutoTick()
while True:
ready_event.wait(5)
if ready_event.is_set() or self._sync_obj.applied_local_log:
break
else:
logger.info('waiting on raft')
def _on_set(self, key: str, value: Dict[str, Any]) -> None:
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 in (self.leader_optime_path, self.status_path) and leader != self._name or \
key in (self.config_path, self.sync_path):
self.event.set()
def _on_delete(self, key: str) -> None:
if key == self.leader_path:
self.event.set()
def set_ttl(self, ttl: int) -> Optional[bool]:
self._ttl = ttl
@property
def ttl(self) -> int:
return self._ttl
def set_retry_timeout(self, retry_timeout: int) -> None:
self._sync_obj.set_retry_timeout(retry_timeout)
def reload_config(self, config: Union['Config', Dict[str, Any]]) -> None:
super(Raft, self).reload_config(config)
globalDnsResolver().setTimeouts(self.ttl, self.loop_wait)
@staticmethod
def member(key: str, value: Dict[str, Any]) -> Member:
return Member.from_node(value['index'], os.path.basename(key), None, value['value'])
def _cluster_from_nodes(self, nodes: Dict[str, Any]) -> Cluster:
# 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 know leader lsn and slots
status = nodes.get(self._STATUS) or nodes.get(self._LEADER_OPTIME)
status = Status.from_node(status and status['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'])
# get failsafe topology
failsafe = nodes.get(self._FAILSAFE)
try:
failsafe = json.loads(failsafe['value']) if failsafe else None
except Exception:
failsafe = None
return Cluster(initialize, config, leader, status, members, failover, sync, history, failsafe)
def _postgresql_cluster_loader(self, path: str) -> Cluster:
"""Load and build the :class:`Cluster` object from DCS, which represents a single PostgreSQL cluster.
:param path: the path in DCS where to load :class:`Cluster` from.
:returns: :class:`Cluster` instance.
"""
response = self._sync_obj.get(path, recursive=True)
if not response:
return Cluster.empty()
nodes = {key[len(path):]: value for key, value in response.items()}
return self._cluster_from_nodes(nodes)
def _mpp_cluster_loader(self, path: str) -> Dict[int, Cluster]:
"""Load and build all PostgreSQL clusters from a single MPP cluster.
:param path: the path in DCS where to load Cluster(s) from.
:returns: all MPP groups as :class:`dict`, with group IDs as keys and :class:`Cluster` objects as values.
"""
clusters: Dict[int, Dict[str, Any]] = defaultdict(dict)
response = self._sync_obj.get(path, recursive=True)
for key, value in (response or {}).items():
key = key[len(path):].split('/', 1)
if len(key) == 2 and self._mpp.group_re.match(key[0]):
clusters[int(key[0])][key[1]] = value
return {group: self._cluster_from_nodes(nodes) for group, nodes in clusters.items()}
def _load_cluster(
self, path: str, loader: Callable[[str], Union[Cluster, Dict[int, Cluster]]]
) -> Union[Cluster, Dict[int, Cluster]]:
return loader(path)
def _write_leader_optime(self, last_lsn: str) -> bool:
return self._sync_obj.set(self.leader_optime_path, last_lsn, timeout=1) is not False
def _write_status(self, value: str) -> bool:
return self._sync_obj.set(self.status_path, value, timeout=1) is not False
def _write_failsafe(self, value: str) -> bool:
return self._sync_obj.set(self.failsafe_path, value, timeout=1) is not False
def _update_leader(self, leader: Leader) -> bool:
ret = self._sync_obj.set(self.leader_path, self._name, ttl=self._ttl,
handle_raft_error=False, prevValue=self._name) is not False
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) -> bool:
return self._sync_obj.set(self.leader_path, self._name, ttl=self._ttl,
handle_raft_error=False, prevExist=False) is not False
def set_failover_value(self, value: str, version: Optional[int] = None) -> bool:
return self._sync_obj.set(self.failover_path, value, prevIndex=version) is not False
def set_config_value(self, value: str, version: Optional[int] = None) -> bool:
return self._sync_obj.set(self.config_path, value, prevIndex=version) is not False
def touch_member(self, data: Dict[str, Any]) -> bool:
value = json.dumps(data, separators=(',', ':'))
return self._sync_obj.set(self.member_path, value, self._ttl, timeout=2) is not False
def take_leader(self) -> bool:
return self._sync_obj.set(self.leader_path, self._name, ttl=self._ttl) is not False
def initialize(self, create_new: bool = True, sysid: str = '') -> bool:
return self._sync_obj.set(self.initialize_path, sysid, prevExist=(not create_new)) is not False
def _delete_leader(self, leader: Leader) -> bool:
return self._sync_obj.delete(self.leader_path, prevValue=self._name, timeout=1)
def cancel_initialization(self) -> bool:
return self._sync_obj.delete(self.initialize_path)
def delete_cluster(self) -> bool:
return self._sync_obj.delete(self.client_path(''), recursive=True)
def set_history_value(self, value: str) -> bool:
return self._sync_obj.set(self.history_path, value) is not False
def set_sync_state_value(self, value: str, version: Optional[int] = None) -> Union[int, bool]:
ret = self._sync_obj.set(self.sync_path, value, prevIndex=version)
if isinstance(ret, dict):
return ret['index']
return ret
def delete_sync_state(self, version: Optional[int] = None) -> bool:
return self._sync_obj.delete(self.sync_path, prevIndex=version)
def watch(self, leader_version: Optional[int], timeout: float) -> bool:
try:
return super(Raft, self).watch(leader_version, timeout)
finally:
self.event.clear()