mirror of
https://github.com/outbackdingo/patroni.git
synced 2026-09-02 17:49:34 +00:00
Alexander Kukushkin
e2faf641d5
Also governor is able to pick up already running master and slave instances without restarting them. In case is you have a lock and postgres is not running behaviour remains the same: it will start master in read only mode and then promote if it still has the lock.
112 lines
4.6 KiB
Python
112 lines
4.6 KiB
Python
import inspect
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import logging
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import time
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from helpers.errors import EtcdError, HealthiestMemberError
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from psycopg2 import OperationalError
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logger = logging.getLogger(__name__)
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def lineno():
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"""Returns the current line number in our program."""
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return inspect.currentframe().f_back.f_lineno
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class Ha:
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def __init__(self, state_handler, etcd):
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self.state_handler = state_handler
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self.etcd = etcd
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self.cluster = None
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def load_cluster_from_etcd(self):
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self.cluster = self.etcd.get_cluster()
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def acquire_lock(self):
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return self.etcd.attempt_to_acquire_leader(self.state_handler.name)
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def update_lock(self):
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return self.etcd.update_leader(self.state_handler.name)
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def is_unlocked(self):
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return not (self.cluster.leader and self.cluster.leader.hostname)
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def has_lock(self):
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logger.info('Lock owner: %s; I am %s', self.cluster.leader.hostname, self.state_handler.name)
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return self.cluster.leader.hostname == self.state_handler.name
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def demote(self):
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return self.state_handler.demote(self.cluster.leader)
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def follow_the_leader(self):
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return self.state_handler.follow_the_leader(self.cluster.leader)
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def run_cycle(self):
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try:
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self.load_cluster_from_etcd()
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if self.is_unlocked():
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if not self.state_handler.is_healthy():
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return 'no action. not healthy enough to do anything.'
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elif self.state_handler.is_healthiest_node(self.cluster.members):
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if self.acquire_lock():
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if not self.state_handler.is_leader():
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self.state_handler.promote()
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return "promoted self to leader by acquiring session lock"
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return "acquired session lock as a leader"
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else:
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self.load_cluster_from_etcd()
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if self.state_handler.is_leader():
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self.demote()
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return "demoted self due after trying and failing to obtain lock"
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else:
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self.follow_the_leader()
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return "following new leader after trying and failing to obtain lock"
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else:
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self.load_cluster_from_etcd()
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if self.state_handler.is_leader():
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self.demote()
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return "demoting self because i am not the healthiest node"
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else:
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self.follow_the_leader()
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return "following a different leader because i am not the healthiest node"
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else:
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if self.has_lock() and not self.state_handler.is_healthy():
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self.state_handler.write_recovery_conf(None)
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self.state_handler.start()
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self.load_cluster_from_etcd()
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if self.has_lock() and self.update_lock():
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try:
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if not self.state_handler.is_leader():
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self.state_handler.promote()
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return "promoted self to leader because i had the session lock"
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else:
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return "no action. i am the leader with the lock"
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finally:
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# create replication slots
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self.state_handler.create_replication_slots([m.hostname for m in self.cluster.members])
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else:
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logger.info("does not have lock")
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if not self.state_handler.is_healthy():
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self.state_handler.write_recovery_conf(self.cluster.leader)
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self.state_handler.start()
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return 'starting as a secondary'
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elif self.state_handler.is_leader():
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self.demote()
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return "demoting self because i do not have the lock and i was a leader"
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else:
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self.follow_the_leader()
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return "no action. i am a secondary and i am following a leader"
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except EtcdError:
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logger.error("Error communicating with Etcd")
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except OperationalError:
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logger.error("Error communicating with Postgresql. Will try again.")
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except HealthiestMemberError:
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logger.error("failed to determine healthiest member fromt etcd")
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def run(self):
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while True:
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self.run_cycle()
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time.sleep(10)
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