PYTHON-2924 Improve test_load_balancing (#955)

Author: ShaneHarvey

test/test_server_selection_in_window.py

@@ -17,7 +17,13 @@
 import os
 import threading
 from test import IntegrationTest, client_context, unittest
-from test.utils import OvertCommandListener, TestCreator, rs_client, wait_until
+from test.utils import (
+    OvertCommandListener,
+    TestCreator,
+    get_pool,
+    rs_client,
+    wait_until,
+)
 from test.utils_selection_tests import create_topology
 
 from pymongo.common import clean_node
@@ -98,11 +104,10 @@ def run(self):
 
 
 class TestProse(IntegrationTest):
-    def frequencies(self, client, listener):
+    def frequencies(self, client, listener, n_finds=10):
         coll = client.test.test
-        N_FINDS = 10
         N_THREADS = 10
-        threads = [FinderThread(coll, N_FINDS) for _ in range(N_THREADS)]
+        threads = [FinderThread(coll, n_finds) for _ in range(N_THREADS)]
         for thread in threads:
             thread.start()
         for thread in threads:
@@ -111,7 +116,7 @@ def frequencies(self, client, listener):
             self.assertTrue(thread.passed)
 
         events = listener.results["started"]
-        self.assertEqual(len(events), N_FINDS * N_THREADS)
+        self.assertEqual(len(events), n_finds * N_THREADS)
         nodes = client.nodes
         self.assertEqual(len(nodes), 2)
         freqs = {address: 0.0 for address in nodes}
@@ -131,10 +136,12 @@ def test_load_balancing(self):
             client_context.mongos_seeds(),
             appName="loadBalancingTest",
             event_listeners=[listener],
-            localThresholdMS=10000,
+            localThresholdMS=30000,
+            minPoolSize=10,
         )
         self.addCleanup(client.close)
         wait_until(lambda: len(client.nodes) == 2, "discover both nodes")
+        wait_until(lambda: len(get_pool(client).sockets) >= 10, "create 10 connections")
         # Delay find commands on
         delay_finds = {
             "configureFailPoint": "failCommand",
@@ -153,7 +160,7 @@ def test_load_balancing(self):
             freqs = self.frequencies(client, listener)
             self.assertLessEqual(freqs[delayed_server], 0.25)
         listener.reset()
-        freqs = self.frequencies(client, listener)
+        freqs = self.frequencies(client, listener, n_finds=100)
         self.assertAlmostEqual(freqs[delayed_server], 0.50, delta=0.15)