PYTHON-5089 Convert test.test_mongos_load_balancing to async (#2107)

Co-authored-by: Noah Stapp <noah.stapp@mongodb.com>

test/asynchronous/test_mongos_load_balancing.py

@@ -0,0 +1,199 @@
+# 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 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()

test/test_mongos_load_balancing.py

@@ -15,8 +15,10 @@
 """Test MongoClient's mongos load balancing using a mock."""
 from __future__ import annotations
 
+import asyncio
 import sys
 import threading
+from test.helpers import ConcurrentRunner
 
 from pymongo.operations import _Op
 
@@ -30,14 +32,10 @@ from pymongo.errors import AutoReconnect, InvalidOperation
 from pymongo.server_selectors import writable_server_selector
 from pymongo.topology_description import TOPOLOGY_TYPE
 
-
-@client_context.require_connection
-@client_context.require_no_load_balancer
-def setUpModule():
-    pass
+_IS_SYNC = True
 
 
-class SimpleOp(threading.Thread):
+class SimpleOp(ConcurrentRunner):
     def __init__(self, client):
         super().__init__()
         self.client = client
@@ -48,15 +46,15 @@ class SimpleOp(threading.Thread):
         self.passed = True  # No exception raised.
 
 
-def do_simple_op(client, nthreads):
-    threads = [SimpleOp(client) for _ in range(nthreads)]
-    for t in threads:
+def do_simple_op(client, ntasks):
+    tasks = [SimpleOp(client) for _ in range(ntasks)]
+    for t in tasks:
         t.start()
 
-    for t in threads:
+    for t in tasks:
         t.join()
 
-    for t in threads:
+    for t in tasks:
         assert t.passed
 
 
@@ -68,6 +66,11 @@ def writable_addresses(topology):
 
 
 class TestMongosLoadBalancing(MockClientTest):
+    @client_context.require_connection
+    @client_context.require_no_load_balancer
+    def setUp(self):
+        super().setUp()
+
     def mock_client(self, **kwargs):
         mock_client = MockClient(
             standalones=[],
@@ -98,7 +101,7 @@ class TestMongosLoadBalancing(MockClientTest):
         wait_until(lambda: len(client.nodes) == 3, "connect to all mongoses")
 
     def test_failover(self):
-        nthreads = 10
+        ntasks = 10
         client = connected(self.mock_client(localThresholdMS=0.001))
         wait_until(lambda: len(client.nodes) == 3, "connect to all mongoses")
 
@@ -118,14 +121,14 @@ class TestMongosLoadBalancing(MockClientTest):
 
             passed.append(True)
 
-        threads = [threading.Thread(target=f) for _ in range(nthreads)]
-        for t in threads:
+        tasks = [ConcurrentRunner(target=f) for _ in range(ntasks)]
+        for t in tasks:
             t.start()
 
-        for t in threads:
+        for t in tasks:
             t.join()
 
-        self.assertEqual(nthreads, len(passed))
+        self.assertEqual(ntasks, len(passed))
 
         # Down host removed from list.
         self.assertEqual(2, len(client.nodes))
@@ -183,8 +186,11 @@ class TestMongosLoadBalancing(MockClientTest):
         client.mock_rtts["a:1"] = 0.045
 
         # Discover only b is within latency window.
+        def predicate():
+            return {("b", 2)} == writable_addresses(topology)
+
         wait_until(
-            lambda: {("b", 2)} == writable_addresses(topology),
+            predicate,
             'discover server "a" is too far',
         )
 

tools/synchro.py

@@ -221,6 +221,7 @@ converted_tests = [
     "test_logger.py",
     "test_max_staleness.py",
     "test_monitoring.py",
+    "test_mongos_load_balancing.py",
     "test_on_demand_csfle.py",
     "test_raw_bson.py",
     "test_read_concern.py",