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import itertools
import unittest
from typing import List, Set, Tuple
from patroni.quorum import QuorumError, QuorumStateResolver
class QuorumTest(unittest.TestCase):
def setUp(self):
self.nesting = 0
self.failures = []
def tearDown(self):
self.assertEqual(self.failures, [])
def check_state_transitions(self, leader: str, quorum: int, voters: Set[str], numsync: int, sync: Set[str],
numsync_confirmed: int, active: Set[str], sync_wanted: int, leader_wanted: str,
expected: List[Tuple[str, str, int, Set[str]]]) -> None:
self.nesting += 1
kwargs = {
'leader': leader, 'quorum': quorum, 'voters': voters,
'numsync': numsync, 'sync': sync, 'numsync_confirmed': numsync_confirmed,
'active': active, 'sync_wanted': sync_wanted, 'leader_wanted': leader_wanted
}
state = {k: v for k, v in kwargs.items()}
result = list(QuorumStateResolver(**kwargs))
self.assertEqual(result, expected)
# also check interrupted transitions
if len(result) > 0 and result[0][0] != 'restart' and kwargs['leader'] == result[0][1]:
if result[0][0] == 'sync':
kwargs.update(numsync=result[0][2], sync=result[0][3])
else:
kwargs.update(quorum=result[0][2], voters=result[0][3])
kwargs['expected'] = expected[1:]
self.check_state_transitions(**kwargs)
self.nesting -= 1
# Now we want to automatically check interruped states, emulating situation when new nodes joined and gone away.
# We are not going to compare exact state transitions, but rather check that they will not produce exceptions.
if self.nesting > 0 or not active > sync:
return
for e in expected:
if e[0] == 'restart' or e[1] != state['leader']:
return
if e[0] == 'sync':
state.update(numsync=e[2], sync=e[3])
else:
state.update(quorum=e[2], voters=e[3])
safety_margin = state['quorum'] + state['numsync'] - len(state['voters'] | state['sync'])
# we are only interested in non-steady cases, when quorum is higher than required by numsync
if safety_margin == 0:
return
# prepare initial state
state = {k: v for k, v in kwargs.items() if k != 'expected'}
def combinations(a):
for r in range(0, len(a) + 1):
for c in itertools.combinations(a, r):
yield set(c)
for e in expected:
if e[0] == 'sync':
state.update(numsync=e[2], sync=e[3])
else:
state.update(quorum=e[2], voters=e[3])
for a in combinations(sync):
# we will check cases with reverting back to active being subsets of sync nodes
state['active'] = a
for c in range(0, len(state['active']) + 1):
# in addition to that we want to consider cases with numsync_confirmed having different values
state['numsync_confirmed'] = c
try:
result = list(QuorumStateResolver(**state))
except Exception as e:
self.failures.append(e)
# besides, we want to make a difference between voters being empty and non-empty
if state['voters']:
voters = state['voters']
quorum = state['quorum']
state.update(voters=set(), quorum=0)
try:
result = list(QuorumStateResolver(**state))
except Exception as e:
self.failures.append(e)
state.update(voters=voters, quorum=quorum)
def test_1111(self):
leader = 'a'
# Add node
self.check_state_transitions(leader=leader, quorum=0, voters=set(),
numsync=0, sync=set(), numsync_confirmed=0, active=set('b'),
sync_wanted=2, leader_wanted=leader, expected=[
('sync', leader, 1, set('b')),
('restart', leader, 0, set()),
])
self.check_state_transitions(leader=leader, quorum=0, voters=set(),
numsync=1, sync=set('b'), numsync_confirmed=1, active=set('b'),
sync_wanted=2, leader_wanted=leader, expected=[
('quorum', leader, 0, set('b'))
])
self.check_state_transitions(leader=leader, quorum=0, voters=set(),
numsync=0, sync=set(), numsync_confirmed=0, active=set('bcde'),
sync_wanted=2, leader_wanted=leader, expected=[
('sync', leader, 2, set('bcde')),
('restart', leader, 0, set()),
])
self.check_state_transitions(leader=leader, quorum=0, voters=set(),
numsync=2, sync=set('bcde'), numsync_confirmed=1, active=set('bcde'),
sync_wanted=2, leader_wanted=leader, expected=[
('quorum', leader, 3, set('bcde')),
])
def test_1222(self):
"""2 node cluster"""
leader = 'a'
# Active set matches state
self.check_state_transitions(leader=leader, quorum=0, voters=set('b'),
numsync=1, sync=set('b'), numsync_confirmed=1, active=set('b'),
sync_wanted=2, leader_wanted=leader, expected=[])
# Add node by increasing quorum
self.check_state_transitions(leader=leader, quorum=0, voters=set('b'),
numsync=1, sync=set('b'), numsync_confirmed=1, active=set('BC'),
sync_wanted=1, leader_wanted=leader, expected=[
('quorum', leader, 1, set('bC')),
('sync', leader, 1, set('bC')),
])
# Add node by increasing sync
self.check_state_transitions(leader=leader, quorum=0, voters=set('b'),
numsync=1, sync=set('b'), numsync_confirmed=1, active=set('bc'),
sync_wanted=2, leader_wanted=leader, expected=[
('sync', leader, 2, set('bc')),
('quorum', leader, 1, set('bc')),
])
# Reduce quorum after added node caught up
self.check_state_transitions(leader=leader, quorum=1, voters=set('bc'),
numsync=2, sync=set('bc'), numsync_confirmed=2, active=set('bc'),
sync_wanted=2, leader_wanted=leader, expected=[
('quorum', leader, 0, set('bc')),
])
# Add multiple nodes by increasing both sync and quorum
self.check_state_transitions(leader=leader, quorum=0, voters=set('b'),
numsync=1, sync=set('b'), numsync_confirmed=1, active=set('BCdE'),
sync_wanted=2, leader_wanted=leader, expected=[
('sync', leader, 2, set('bC')),
('quorum', leader, 3, set('bCdE')),
('sync', leader, 2, set('bCdE')),
])
# Reduce quorum after added nodes caught up
self.check_state_transitions(leader=leader, quorum=3, voters=set('bcde'),
numsync=2, sync=set('bcde'), numsync_confirmed=3, active=set('bcde'),
sync_wanted=2, leader_wanted=leader, expected=[
('quorum', leader, 2, set('bcde')),
])
# Primary is alone
self.check_state_transitions(leader=leader, quorum=0, voters=set('b'),
numsync=1, sync=set('b'), numsync_confirmed=0, active=set(),
sync_wanted=1, leader_wanted=leader, expected=[
('quorum', leader, 0, set()),
('sync', leader, 0, set()),
])
# Swap out sync replica
self.check_state_transitions(leader=leader, quorum=0, voters=set('b'),
numsync=1, sync=set('b'), numsync_confirmed=0, active=set('c'),
sync_wanted=1, leader_wanted=leader, expected=[
('quorum', leader, 0, set()),
('sync', leader, 1, set('c')),
('restart', leader, 0, set()),
])
# Update quorum when added node caught up
self.check_state_transitions(leader=leader, quorum=0, voters=set(),
numsync=1, sync=set('c'), numsync_confirmed=1, active=set('c'),
sync_wanted=1, leader_wanted=leader, expected=[
('quorum', leader, 0, set('c')),
])
def test_1233(self):
"""Interrupted transition from 2 node cluster to 3 node fully sync cluster"""
leader = 'a'
# Node c went away, transition back to 2 node cluster
self.check_state_transitions(leader=leader, quorum=0, voters=set('b'),
numsync=2, sync=set('bc'), numsync_confirmed=1, active=set('b'),
sync_wanted=2, leader_wanted=leader, expected=[
('sync', leader, 1, set('b')),
])
# Node c is available transition to larger quorum set, but not yet caught up.
self.check_state_transitions(leader=leader, quorum=0, voters=set('b'),
numsync=2, sync=set('bc'), numsync_confirmed=1, active=set('bc'),
sync_wanted=2, leader_wanted=leader, expected=[
('quorum', leader, 1, set('bc')),
])
# Add in a new node at the same time, but node c didn't caught up yet
self.check_state_transitions(leader=leader, quorum=0, voters=set('b'),
numsync=2, sync=set('bc'), numsync_confirmed=1, active=set('bcd'),
sync_wanted=2, leader_wanted=leader, expected=[
('quorum', leader, 2, set('bcd')),
('sync', leader, 2, set('bcd')),
])
# All sync nodes caught up, reduce quorum
self.check_state_transitions(leader=leader, quorum=2, voters=set('bcd'),
numsync=2, sync=set('bcd'), numsync_confirmed=3, active=set('bcd'),
sync_wanted=2, leader_wanted=leader, expected=[
('quorum', leader, 1, set('bcd')),
])
# Change replication factor at the same time
self.check_state_transitions(leader=leader, quorum=0, voters=set('b'),
numsync=2, sync=set('bc'), numsync_confirmed=1, active=set('bc'),
sync_wanted=1, leader_wanted=leader, expected=[
('quorum', leader, 1, set('bc')),
('sync', leader, 1, set('bc')),
])
def test_2322(self):
"""Interrupted transition from 2 node cluster to 3 node cluster with replication factor 2"""
leader = 'a'
# Node c went away, transition back to 2 node cluster
self.check_state_transitions(leader=leader, quorum=1, voters=set('bc'),
numsync=1, sync=set('b'), numsync_confirmed=1, active=set('b'),
sync_wanted=1, leader_wanted=leader, expected=[
('quorum', leader, 0, set('b')),
])
# Node c is available transition to larger quorum set.
self.check_state_transitions(leader=leader, quorum=1, voters=set('bc'),
numsync=1, sync=set('b'), numsync_confirmed=1, active=set('bc'),
sync_wanted=1, leader_wanted=leader, expected=[
('sync', leader, 1, set('bc')),
])
# Add in a new node at the same time
self.check_state_transitions(leader=leader, quorum=1, voters=set('bc'),
numsync=1, sync=set('b'), numsync_confirmed=1, active=set('bcd'),
sync_wanted=1, leader_wanted=leader, expected=[
('sync', leader, 1, set('bc')),
('quorum', leader, 2, set('bcd')),
('sync', leader, 1, set('bcd')),
])
# Convert to a fully synced cluster
self.check_state_transitions(leader=leader, quorum=1, voters=set('bc'),
numsync=1, sync=set('b'), numsync_confirmed=1, active=set('bc'),
sync_wanted=2, leader_wanted=leader, expected=[
('sync', leader, 2, set('bc')),
])
# Reduce quorum after all nodes caught up
self.check_state_transitions(leader=leader, quorum=1, voters=set('bc'),
numsync=2, sync=set('bc'), numsync_confirmed=2, active=set('bc'),
sync_wanted=2, leader_wanted=leader, expected=[
('quorum', leader, 0, set('bc')),
])
def test_3535(self):
leader = 'a'
# remove nodes
self.check_state_transitions(leader=leader, quorum=2, voters=set('bcde'),
numsync=2, sync=set('bcde'), numsync_confirmed=2, active=set('bc'),
sync_wanted=2, leader_wanted=leader, expected=[
('sync', leader, 2, set('bc')),
('quorum', leader, 0, set('bc')),
])
self.check_state_transitions(leader=leader, quorum=2, voters=set('bcde'),
numsync=2, sync=set('bcde'), numsync_confirmed=3, active=set('bcd'),
sync_wanted=2, leader_wanted=leader, expected=[
('sync', leader, 2, set('bcd')),
('quorum', leader, 1, set('bcd')),
])
# remove nodes and decrease sync
self.check_state_transitions(leader=leader, quorum=2, voters=set('bcde'),
numsync=2, sync=set('bcde'), numsync_confirmed=2, active=set('bc'),
sync_wanted=1, leader_wanted=leader, expected=[
('sync', leader, 2, set('bc')),
('quorum', leader, 1, set('bc')),
('sync', leader, 1, set('bc')),
])
self.check_state_transitions(leader=leader, quorum=1, voters=set('bcde'),
numsync=3, sync=set('bcde'), numsync_confirmed=2, active=set('bc'),
sync_wanted=1, leader_wanted=leader, expected=[
('sync', leader, 3, set('bcd')),
('quorum', leader, 1, set('bc')),
('sync', leader, 1, set('bc')),
])
# Increase replication factor and decrease quorum
self.check_state_transitions(leader=leader, quorum=2, voters=set('bcde'),
numsync=2, sync=set('bcde'), numsync_confirmed=2, active=set('bcde'),
sync_wanted=3, leader_wanted=leader, expected=[
('sync', leader, 3, set('bcde')),
])
# decrease quorum after more nodes caught up
self.check_state_transitions(leader=leader, quorum=2, voters=set('bcde'),
numsync=3, sync=set('bcde'), numsync_confirmed=3, active=set('bcde'),
sync_wanted=3, leader_wanted=leader, expected=[
('quorum', leader, 1, set('bcde')),
])
# Add node with decreasing sync and increasing quorum
self.check_state_transitions(leader=leader, quorum=2, voters=set('bcde'),
numsync=2, sync=set('bcde'), numsync_confirmed=2, active=set('bcdef'),
sync_wanted=1, leader_wanted=leader, expected=[
# increase quorum by 2, 1 for added node and another for reduced sync
('quorum', leader, 4, set('bcdef')),
# now reduce replication factor to requested value
('sync', leader, 1, set('bcdef')),
])
# Remove node with increasing sync and decreasing quorum
self.check_state_transitions(leader=leader, quorum=2, voters=set('bcde'),
numsync=2, sync=set('bcde'), numsync_confirmed=2, active=set('bcd'),
sync_wanted=3, leader_wanted=leader, expected=[
# node e removed from sync with replication factor increase
('sync', leader, 3, set('bcd')),
# node e removed from voters with quorum decrease
('quorum', leader, 1, set('bcd')),
])
def test_remove_nosync_node(self):
leader = 'a'
self.check_state_transitions(leader=leader, quorum=0, voters=set('bc'),
numsync=2, sync=set('bc'), numsync_confirmed=1, active=set('b'),
sync_wanted=2, leader_wanted=leader, expected=[
('quorum', leader, 0, set('b')),
('sync', leader, 1, set('b'))
])
def test_swap_sync_node(self):
leader = 'a'
self.check_state_transitions(leader=leader, quorum=0, voters=set('bc'),
numsync=2, sync=set('bc'), numsync_confirmed=1, active=set('bd'),
sync_wanted=2, leader_wanted=leader, expected=[
('quorum', leader, 0, set('b')),
('sync', leader, 2, set('bd')),
('quorum', leader, 1, set('bd'))
])
def test_promotion(self):
# Beginning stat: 'a' in the primary, 1 of bcd in sync
# a fails, c gets quorum votes and promotes
self.check_state_transitions(leader='a', quorum=2, voters=set('bcd'),
numsync=0, sync=set(), numsync_confirmed=0, active=set(),
sync_wanted=1, leader_wanted='c', expected=[
('sync', 'a', 1, set('abd')), # set a and b to sync
('quorum', 'c', 2, set('abd')), # set c as a leader and move a to voters
# and stop because there are no active nodes
])
# next loop, b managed to reconnect
self.check_state_transitions(leader='c', quorum=2, voters=set('abd'),
numsync=1, sync=set('abd'), numsync_confirmed=0, active=set('b'),
sync_wanted=1, leader_wanted='c', expected=[
('sync', 'c', 1, set('b')), # remove a from sync as inactive
('quorum', 'c', 0, set('b')), # remove a from voters and reduce quorum
])
# alternative reality: next loop, no one reconnected
self.check_state_transitions(leader='c', quorum=2, voters=set('abd'),
numsync=1, sync=set('abd'), numsync_confirmed=0, active=set(),
sync_wanted=1, leader_wanted='c', expected=[
('quorum', 'c', 0, set()),
('sync', 'c', 0, set()),
])
def test_nonsync_promotion(self):
# Beginning state: 1 of bc in sync. e.g. (a primary, ssn = ANY 1 (b c))
# a fails, d sees b and c, knows that it is in sync and decides to promote.
# We include in sync state former primary increasing replication factor
# and let situation resolve. Node d ssn=ANY 1 (b c)
leader = 'd'
self.check_state_transitions(leader='a', quorum=1, voters=set('bc'),
numsync=0, sync=set(), numsync_confirmed=0, active=set(),
sync_wanted=1, leader_wanted=leader, expected=[
# Set a, b, and c to sync and increase replication factor
('sync', 'a', 2, set('abc')),
# Set ourselves as the leader and move the old leader to voters
('quorum', leader, 1, set('abc')),
# and stop because there are no active nodes
])
# next loop, b and c managed to reconnect
self.check_state_transitions(leader=leader, quorum=1, voters=set('abc'),
numsync=2, sync=set('abc'), numsync_confirmed=0, active=set('bc'),
sync_wanted=1, leader_wanted=leader, expected=[
('sync', leader, 2, set('bc')), # Remove a from being synced to.
('quorum', leader, 1, set('bc')), # Remove a from quorum
('sync', leader, 1, set('bc')), # Can now reduce replication factor back
])
# alternative reality: next loop, no one reconnected
self.check_state_transitions(leader=leader, quorum=1, voters=set('abc'),
numsync=2, sync=set('abc'), numsync_confirmed=0, active=set(),
sync_wanted=1, leader_wanted=leader, expected=[
('quorum', leader, 0, set()),
('sync', leader, 0, set()),
])
def test_invalid_states(self):
leader = 'a'
# Main invariant is not satisfied, system is in an unsafe state
resolver = QuorumStateResolver(leader=leader, quorum=0, voters=set('bc'),
numsync=1, sync=set('bc'), numsync_confirmed=1,
active=set('bc'), sync_wanted=1, leader_wanted=leader)
self.assertRaises(QuorumError, resolver.check_invariants)
self.assertEqual(list(resolver), [
('quorum', leader, 1, set('bc'))
])
# Quorum and sync states mismatched, somebody other than Patroni modified system state
resolver = QuorumStateResolver(leader=leader, quorum=1, voters=set('bc'),
numsync=2, sync=set('bd'), numsync_confirmed=1,
active=set('bd'), sync_wanted=1, leader_wanted=leader)
self.assertRaises(QuorumError, resolver.check_invariants)
self.assertEqual(list(resolver), [
('quorum', leader, 1, set('bd')),
('sync', leader, 1, set('bd')),
])
self.assertTrue(repr(resolver.sync).startswith('<CaseInsensitiveSet'))
def test_sync_high_quorum_low_safety_margin_high(self):
leader = 'a'
self.check_state_transitions(leader=leader, quorum=2, voters=set('bcdef'),
numsync=4, sync=set('bcdef'), numsync_confirmed=3, active=set('bcdef'),
sync_wanted=2, leader_wanted=leader, expected=[
('quorum', leader, 3, set('bcdef')), # Adjust quorum requirements
('sync', leader, 2, set('bcdef')), # Reduce synchronization
])
def test_quorum_update(self):
resolver = QuorumStateResolver(leader='a', quorum=1, voters=set('bc'), numsync=1, sync=set('bc'),
numsync_confirmed=1, active=set('bc'), sync_wanted=1, leader_wanted='a')
self.assertRaises(QuorumError, list, resolver.quorum_update(-1, set()))
self.assertRaises(QuorumError, list, resolver.quorum_update(1, set()))
def test_sync_update(self):
resolver = QuorumStateResolver(leader='a', quorum=1, voters=set('bc'), numsync=1, sync=set('bc'),
numsync_confirmed=1, active=set('bc'), sync_wanted=1, leader_wanted='a')
self.assertRaises(QuorumError, list, resolver.sync_update(-1, set()))
self.assertRaises(QuorumError, list, resolver.sync_update(1, set()))
def test_remove_nodes_with_decreasing_sync(self):
leader = 'a'
# Remove node with decreasing sync
self.check_state_transitions(leader=leader, quorum=1, voters=set('bcdef'),
numsync=4, sync=set('bcdef'), numsync_confirmed=2, active=set('bcd'),
sync_wanted=2, leader_wanted=leader, expected=[
# node f removed from sync
('sync', leader, 4, set('bcde')),
# nodes e and f removed from voters with quorum decrease
('quorum', leader, 1, set('bcd')),
# node e removed from sync with replication factor decrease
('sync', leader, 2, set('bcd')),
])
# Interrupted state, and node g joined
self.check_state_transitions(leader=leader, quorum=1, voters=set('bcdef'),
numsync=4, sync=set('bcde'), numsync_confirmed=2, active=set('bcdg'),
sync_wanted=2, leader_wanted=leader, expected=[
# remove nodes e and f from voters
('quorum', leader, 1, set('bcd')),
# remove node e from sync and reduce replication factor
('sync', leader, 3, set('bcd')),
# add node g to voters with quorum increase
('quorum', leader, 2, set('bcdg')),
# add node g to sync and reduce replication factor
('sync', leader, 2, set('bcdg')),
])
# node f returned
self.check_state_transitions(leader=leader, quorum=1, voters=set('bcdef'),
numsync=4, sync=set('bcde'), numsync_confirmed=2, active=set('bcdf'),
sync_wanted=2, leader_wanted=leader, expected=[
# replace node e with f in sync
('sync', leader, 4, set('bcdf')),
# remove nodes e from voters with quorum decrease
('quorum', leader, 2, set('bcdf')),
# reduce replication factor as it was requested
('sync', leader, 2, set('bcdf')),
])
# node e returned
self.check_state_transitions(leader=leader, quorum=1, voters=set('bcdef'),
numsync=4, sync=set('bcde'), numsync_confirmed=2, active=set('bcde'),
sync_wanted=2, leader_wanted=leader, expected=[
# remove nodes f from voters with quorum decrease
('quorum', leader, 2, set('bcde')),
# reduce replication factor as it was requested
('sync', leader, 2, set('bcde')),
])
# node b is also lost
self.check_state_transitions(leader=leader, quorum=1, voters=set('bcdef'),
numsync=4, sync=set('bcde'), numsync_confirmed=2, active=set('cd'),
sync_wanted=1, leader_wanted=leader, expected=[
# remove nodes b, e, and f from voters
('quorum', leader, 1, set('cd')),
# remove nodes b and e from sync with replication factor decrease
('sync', leader, 1, set('cd')),
])
def test_empty_ssn(self):
# Beginning stat: 'a' in the primary, 1 of bc in sync
# a fails, c gets quorum votes and promotes
self.check_state_transitions(leader='a', quorum=1, voters=set('bc'),
numsync=1, sync=set(), numsync_confirmed=0, active=set(),
sync_wanted=1, leader_wanted='c', expected=[
('sync', 'a', 1, set('ab')), # remove a from sync as inactive
('quorum', 'c', 1, set('ab')), # set c as a leader and move a to voters
# and stop because there are no active nodes
])
# next loop, b managed to reconnect
self.check_state_transitions(leader='c', quorum=1, voters=set('ab'),
numsync=1, sync=set('ab'), numsync_confirmed=0, active=set('b'),
sync_wanted=1, leader_wanted='c', expected=[
('sync', 'c', 1, set('b')), # remove a from sync as inactive
('quorum', 'c', 0, set('b')), # remove a from voters and reduce quorum
])
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