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# Copyright 2015-present MongoDB, Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Test AsyncMongoClient's mongos load balancing using a mock."""
from __future__ import annotations
import asyncio
import sys
import threading
from test.asynchronous.helpers import ConcurrentRunner
from pymongo.operations import _Op
sys.path[0:0] = [""]
from test.asynchronous import AsyncMockClientTest, async_client_context, connected, unittest
from test.asynchronous.pymongo_mocks import AsyncMockClient
from test.utils_shared import async_wait_until
from pymongo.errors import AutoReconnect, InvalidOperation
from pymongo.server_selectors import writable_server_selector
from pymongo.topology_description import TOPOLOGY_TYPE
_IS_SYNC = False
class SimpleOp(ConcurrentRunner):
def __init__(self, client):
super().__init__()
self.client = client
self.passed = False
async def run(self):
await self.client.db.command("ping")
self.passed = True # No exception raised.
async def do_simple_op(client, ntasks):
tasks = [SimpleOp(client) for _ in range(ntasks)]
for t in tasks:
await t.start()
for t in tasks:
await t.join()
for t in tasks:
assert t.passed
async def writable_addresses(topology):
return {
server.description.address
for server in await topology.select_servers(writable_server_selector, _Op.TEST)
}
class TestMongosLoadBalancing(AsyncMockClientTest):
@async_client_context.require_connection
@async_client_context.require_no_load_balancer
async def asyncSetUp(self):
await super().asyncSetUp()
def mock_client(self, **kwargs):
mock_client = AsyncMockClient(
standalones=[],
members=[],
mongoses=["a:1", "b:2", "c:3"],
host="a:1,b:2,c:3",
connect=False,
**kwargs,
)
self.addAsyncCleanup(mock_client.aclose)
# Latencies in seconds.
mock_client.mock_rtts["a:1"] = 0.020
mock_client.mock_rtts["b:2"] = 0.025
mock_client.mock_rtts["c:3"] = 0.045
return mock_client
async def test_lazy_connect(self):
# While connected() ensures we can trigger connection from the main
# thread and wait for the monitors, this test triggers connection from
# several threads at once to check for data races.
nthreads = 10
client = self.mock_client()
self.assertEqual(0, len(client.nodes))
# Trigger initial connection.
await do_simple_op(client, nthreads)
await async_wait_until(lambda: len(client.nodes) == 3, "connect to all mongoses")
async def test_failover(self):
ntasks = 10
client = await connected(self.mock_client(localThresholdMS=0.001))
await async_wait_until(lambda: len(client.nodes) == 3, "connect to all mongoses")
# Our chosen mongos goes down.
client.kill_host("a:1")
# Trigger failover to higher-latency nodes. AutoReconnect should be
# raised at most once in each thread.
passed = []
async def f():
try:
await client.db.command("ping")
except AutoReconnect:
# Second attempt succeeds.
await client.db.command("ping")
passed.append(True)
tasks = [ConcurrentRunner(target=f) for _ in range(ntasks)]
for t in tasks:
await t.start()
for t in tasks:
await t.join()
self.assertEqual(ntasks, len(passed))
# Down host removed from list.
self.assertEqual(2, len(client.nodes))
async def test_local_threshold(self):
client = await connected(self.mock_client(localThresholdMS=30))
self.assertEqual(30, client.options.local_threshold_ms)
await async_wait_until(lambda: len(client.nodes) == 3, "connect to all mongoses")
topology = client._topology
# All are within a 30-ms latency window, see self.mock_client().
self.assertEqual({("a", 1), ("b", 2), ("c", 3)}, await writable_addresses(topology))
# No error
await client.admin.command("ping")
client = await connected(self.mock_client(localThresholdMS=0))
self.assertEqual(0, client.options.local_threshold_ms)
# No error
await client.db.command("ping")
# Our chosen mongos goes down.
client.kill_host("{}:{}".format(*next(iter(client.nodes))))
try:
await client.db.command("ping")
except:
pass
# We eventually connect to a new mongos.
async def connect_to_new_mongos():
try:
return await client.db.command("ping")
except AutoReconnect:
pass
await async_wait_until(connect_to_new_mongos, "connect to a new mongos")
async def test_load_balancing(self):
# Although the server selection JSON tests already prove that
# select_servers works for sharded topologies, here we do an end-to-end
# test of discovering servers' round trip times and configuring
# localThresholdMS.
client = await connected(self.mock_client())
await async_wait_until(lambda: len(client.nodes) == 3, "connect to all mongoses")
# Prohibited for topology type Sharded.
with self.assertRaises(InvalidOperation):
await client.address
topology = client._topology
self.assertEqual(TOPOLOGY_TYPE.Sharded, topology.description.topology_type)
# a and b are within the 15-ms latency window, see self.mock_client().
self.assertEqual({("a", 1), ("b", 2)}, await writable_addresses(topology))
client.mock_rtts["a:1"] = 0.045
# Discover only b is within latency window.
async def predicate():
return {("b", 2)} == await writable_addresses(topology)
await async_wait_until(
predicate,
'discover server "a" is too far',
)
if __name__ == "__main__":
unittest.main()
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