test for two step rebalancing; use random seed for reproducible test results

tests/test_dataDistribution.py

@@ -20,6 +20,8 @@ class TestDataDistribution(unittest.TestCase):
             capacities[new_osd.uuid] = {}
             capacities[new_osd.uuid][capacity_key] = osd_capacity
 
+        random.seed(9234)
+
     def test_totally_random_distribution(self):
         # generate some random distributions and check whether they are different
         max_osd_total_folder_size = 0
@@ -247,6 +249,43 @@ class TestDataDistribution(unittest.TestCase):
         self.assertEqual(0, min(total_folder_sizes))
         self.assertEqual(2, max(total_folder_sizes))
 
+    def test_rebalance_two_steps(self):
+        folder_sizes = [1]
+        num_folders = 12
+        osd_bandwidths = [10]
+        num_osds = 4
+
+        distribution = dataDistribution.DataDistribution()
+        distribution.add_osd_list(create_test_osd_list(num_osds, osd_bandwidths))
+        distribution.add_folders(create_test_folder_list(num_folders, folder_sizes), random_osd_assignment=True)
+
+        distribution.rebalance_two_steps()
+
+        osds = distribution.get_osd_list()
+        total_folder_sizes = list(map(lambda x: distribution.OSDs[x].total_folder_size, osds))
+
+        # 12 unit size folders on 4 OSD => each should have 3 files
+        self.assertEqual(3, min(total_folder_sizes))
+        self.assertEqual(3, max(total_folder_sizes))
+        self.assertEqual(12, sum(total_folder_sizes))
+
+        # same test with one more folder size
+        folder_sizes = [1, 2]
+
+        distribution = dataDistribution.DataDistribution()
+        distribution.add_osd_list(create_test_osd_list(num_osds, osd_bandwidths))
+        distribution.add_folders(create_test_folder_list(num_folders, folder_sizes), random_osd_assignment=True)
+
+        distribution.rebalance_two_steps()
+
+        osds = distribution.get_osd_list()
+        total_folder_sizes = list(map(lambda x: distribution.OSDs[x].total_folder_size, osds))
+
+        self.assertEqual(9, min(total_folder_sizes))
+        self.assertEqual(9, max(total_folder_sizes))
+        self.assertEqual(36, sum(total_folder_sizes))
+
+
 def create_test_osd_list(num_osds, osd_capacities):
     test_osds = []
     for i in range(0, num_osds):