def test_cannot_initialize_backend(self):
msg = (
"Cannot initialize `MIGRATION_QUORUM_BACKEND` backend "
"'syzygy.quorum.backends.cache.CacheQuorum' with {'unsupported': True}"
)
with self.assertRaisesMessage(ImproperlyConfigured, msg):
join_quorum("foo", 1)
def test_misconfigured_setting(self):
msg = (
"The `MIGRATION_QUORUM_BACKEND` setting must either be an import "
"path string or a dict with a 'backend' path key string"
)
with self.assertRaisesMessage(ImproperlyConfigured, msg):
join_quorum("foo", 1)
def test_missing_setting(self):
msg = (
"The `MIGRATION_QUORUM_BACKEND` setting must be configured "
"for syzygy.quorum to be used"
)
with self.assertRaisesMessage(ImproperlyConfigured, msg):
join_quorum("foo", 1)
def test_namespace_reuse(self):
namespace = str(uuid.uuid4())
self.assertFalse(join_quorum(namespace, 2))
self.assertTrue(join_quorum(namespace, 2))
self.assertTrue(poll_quorum(namespace, 2))
# Once quorum is reached its associated is immediately cleared and reusable.
self.assertFalse(join_quorum(namespace, 2))
self.assertTrue(join_quorum(namespace, 2))
self.assertTrue(poll_quorum(namespace, 2))
def _handle_quorum(self, quorum: int, quorum_timeout: int,
options: dict) -> Iterator[bool]:
"""
Context manager that handles migration application quorum by only
allowing a single caller to proceed with application and preventing
exit attempts until the application is completes.
This ensures only a single invocation is allowed to proceed once
quorum is reached and that context can only be exited once the
invocation application succeeds.
"""
if quorum < 2:
yield True
return
verbosity = options["verbosity"]
plan = self._get_plan(**options)
if not plan:
yield True
return
database = options["database"]
plan_hash = hash_plan(plan)
pre_namespace = f"pre:{database}:{plan_hash}"
post_namespace = f"post:{database}:{plan_hash}"
if join_quorum(pre_namespace, quorum):
if verbosity:
self.stdout.write(
"Reached pre-migrate quorum, proceeding with planned migrations..."
)
yield True
if verbosity:
self.stdout.write("Waiting for post-migrate quorum...")
duration = self._join_or_poll_until_quorum(post_namespace, quorum,
quorum_timeout)
if verbosity:
self.stdout.write(
f"Reached post-migrate quorum after {duration:.2f}s...")
return
yield False
if verbosity:
self.stdout.write("Waiting for pre-migrate quorum...")
duration = self._poll_until_quorum(pre_namespace, quorum,
quorum_timeout)
if verbosity:
self.stdout.write(
f"Reached pre-migrate quorum after {duration:.2f}s...")
self.stdout.write(
"Waiting for migrations to be applied by remote party...")
duration = self._join_or_poll_until_quorum(post_namespace, quorum,
quorum_timeout)
if verbosity:
self.stdout.write(
f"Reached post-migrate quorum after {duration:.2f}s...")
self.stdout.write("Migrations applied by remote party")
return
def _join_or_poll_until_quorum(self, namespace: str, quorum: int,
quorum_timeout: int) -> float:
if join_quorum(namespace, quorum):
return 0
return self._poll_until_quorum(namespace, quorum, quorum_timeout)
def achieve_quorum(namespace):
if join_quorum(namespace, quorum):
return True
while not poll_quorum(namespace, quorum):
time.sleep(0.01)
return False
def test_multiple(self):
namespace = str(uuid.uuid4())
self.assertFalse(join_quorum(namespace, 2))
self.assertFalse(poll_quorum(namespace, 2))
self.assertTrue(join_quorum(namespace, 2))
self.assertTrue(poll_quorum(namespace, 2))
def test_cannot_import_backend(self):
msg = "Cannot import `MIGRATION_QUORUM_BACKEND` backend 'syzygy.void'"
with self.assertRaisesMessage(ImproperlyConfigured, msg):
join_quorum("foo", 1)