def test_readonly_three_replicas(self):
set_thread_readonly_db()
replica0 = 'my-replica-db0'
replica1 = 'my-replica-db1'
replica2 = 'my-replica-db2'
pool = {
replica0: 1,
replica1: 1,
replica2: 1,
}
replicas = pool.keys()
with override_settings(DATABASE_POOL=pool):
router = DBRouter()
out0 = router.db_for_read(Submission)
self.assertIn(out0, replicas)
out1 = router.db_for_read(Submission)
self.assertIn(out1, replicas)
self.assertNotEqual(out0, out1)
out2 = router.db_for_read(Submission)
self.assertIn(out2, replicas)
self.assertNotEqual(out1, out2)
out3 = router.db_for_read(Submission)
# Round-robin should have come around by now
self.assertEqual(out3, out0)
self.assertFalse(was_db_written())
def test_readonly_one_replica(self):
set_thread_readonly_db()
replica = 'my-only-replica-db'
pool = {
replica: 1
}
with override_settings(DATABASE_POOL=pool):
router = DBRouter()
out = router.db_for_read(Submission)
self.assertEqual(replica, out)
out = router.db_for_read(Submission)
self.assertEqual(replica, out)
self.assertFalse(was_db_written())
def update_recent_events():
"""
Compute recent events and other statistics and cache them.
"""
logger.debug("update_recent_events: started")
try:
# No middleware on tasks, so this won't get set otherwise.
# Tell the DB router this thread only needs to read the DB, not write.
# We run this task frequently, so it's worthwhile.
set_thread_readonly_db()
votes = Vote.objects.select_related(
"voter", "voter__user", "submission").filter(
submission__approved=True, submission__duplicate_of__isnull=True).exclude(
voter=F('submission__voter')).order_by("-id")[:10]
submissions = Submission.objects.select_related(
"voter", "voter__user").filter(
approved=True, duplicate_of__isnull=True).order_by("-id")[:10]
entries = list(votes) + list(submissions)
entries = sorted(entries, key=lambda x: x.created_at, reverse=True)[:10]
cache.set(RECENT_EVENTS_CACHE_ENTRY, entries, 24*3600)
number_of_votes = Vote.objects.count()
cache.set(NUMBER_OF_VOTES_CACHE_ENTRY, number_of_votes, 24*3600)
logger.debug("There are %d entries" % len(entries))
logger.debug("There are %d votes" % number_of_votes)
except:
# This task runs too frequently to report a recurring problem every time
# it happens.
global exception_logged
if not exception_logged:
logger.exception("Unexpected exception in update_recent_events")
exception_logged = True
finally:
# Be a good citizen and reset the worker's thread to the default state
set_thread_readwrite_db()
def test_with_readonly_db_when_readonly(self):
set_thread_readonly_db()
assert not is_thread_readwrite()
with readonly_db():
assert not is_thread_readwrite()
assert not is_thread_readwrite()