SERVER-39138: Properly handle new suites when splitting suites

(cherry picked from commit eee822dc06f5f1514cb1a3f5930940ccf95f2e41)

2 files changed, 30 insertions, 5 deletions

diff --git a/buildscripts/evergreen_generate_resmoke_tasks.py b/buildscripts/evergreen_generate_resmoke_tasks.py
index 19fd7c4662e..0108c889f4f 100755
--- a/buildscripts/evergreen_generate_resmoke_tasks.py
+++ b/buildscripts/evergreen_generate_resmoke_tasks.py
@@ -100,8 +100,9 @@ def get_config_options(cmd_line_options, config_file):
     # pylint: disable=too-many-locals
     config_file_data = read_config.read_config_file(config_file)
 
-    fallback_num_sub_suites = read_config.get_config_value(
-        "fallback_num_sub_suites", cmd_line_options, config_file_data, required=True)
+    fallback_num_sub_suites = int(
+        read_config.get_config_value("fallback_num_sub_suites", cmd_line_options, config_file_data,
+                                     required=True))
     max_sub_suites = read_config.get_config_value("max_sub_suites", cmd_line_options,
                                                   config_file_data)
     project = read_config.get_config_value("project", cmd_line_options, config_file_data,
@@ -534,6 +535,10 @@ class Main(object):
         try:
             evg_stats = self.get_evg_stats(self.config_options.project, start_date, end_date,
                                            self.config_options.task, self.config_options.variant)
+            if not evg_stats:
+                # This is probably a new suite, since there is no test history, just use the
+                # fallback values.
+                return self.calculate_fallback_suites()
             target_execution_time_secs = self.config_options.target_resmoke_time * 60
             return self.calculate_suites_from_evg_stats(evg_stats, target_execution_time_secs)
         except requests.HTTPError as err:
@@ -572,9 +577,9 @@ class Main(object):
     def calculate_fallback_suites(self):
         """Divide tests into a fixed number of suites."""
         num_suites = self.config_options.fallback_num_sub_suites
-        tests = self.list_tests()
+        self.test_list = self.list_tests()
         suites = [Suite() for _ in range(num_suites)]
-        for idx, test_file in enumerate(tests):
+        for idx, test_file in enumerate(self.test_list):
             suites[idx % num_suites].add_test(test_file, 0)
         return suites
 
diff --git a/buildscripts/tests/test_evergreen_generate_resmoke_tasks.py b/buildscripts/tests/test_evergreen_generate_resmoke_tasks.py
index 767b8891922..af6fdadf9d1 100644
--- a/buildscripts/tests/test_evergreen_generate_resmoke_tasks.py
+++ b/buildscripts/tests/test_evergreen_generate_resmoke_tasks.py
@@ -473,6 +473,7 @@ class MainTest(unittest.TestCase):
                 self.assertEqual(10, len(suite.tests))
 
     def test_calculate_suites_fallback(self):
+        n_tests = 100
         response = Mock()
         response.status_code = requests.codes.SERVICE_UNAVAILABLE
         evg = Mock()
@@ -482,14 +483,33 @@ class MainTest(unittest.TestCase):
         main.options = Mock()
         main.options.execution_time_minutes = 10
         main.config_options = self.get_mock_options()
-        main.list_tests = Mock(return_value=["test{}.js".format(i) for i in range(100)])
+        main.list_tests = Mock(return_value=["test{}.js".format(i) for i in range(n_tests)])
+
+        suites = main.calculate_suites(_DATE, _DATE)
+
+        self.assertEqual(main.config_options.fallback_num_sub_suites, len(suites))
+        for suite in suites:
+            self.assertEqual(50, len(suite.tests))
 
+        self.assertEqual(n_tests, len(main.test_list))
+
+    def test_calculate_suites_uses_fallback_for_no_results(self):
+        n_tests = 100
+        evg = Mock()
+        evg.test_stats.return_value = []
+
+        main = grt.Main(evg)
+        main.options = Mock()
+        main.config_options = self.get_mock_options()
+        main.list_tests = Mock(return_value=["test{}.js".format(i) for i in range(n_tests)])
         suites = main.calculate_suites(_DATE, _DATE)
 
         self.assertEqual(main.config_options.fallback_num_sub_suites, len(suites))
         for suite in suites:
             self.assertEqual(50, len(suite.tests))
 
+        self.assertEqual(n_tests, len(main.test_list))
+
     def test_calculate_suites_error(self):
         response = Mock()
         response.status_code = requests.codes.INTERNAL_SERVER_ERROR