[flow counter] Fix issue: should not compare str with int (#2001)

*When clearing stats, current flow counter stats is serialized to a file for further compare. All stats value is saved as string value. When doing diff, the loaded stats value shall be convert into int and do the compare. The PR is to fix this issue.

scripts/flow_counters_stat

@@ -230,21 +230,21 @@ class FlowCounterStats(object):
                     # counter OID is changed.
                     old_values[-1] = values[-1]
                     for i in diff_column_positions:
-                        old_values[i] = 0
+                        old_values[i] = '0'
                         values[i] = ns_diff(values[i], old_values[i])
                     need_update_cache = True
                     continue
 
                 has_negative_diff = False
                 for i in diff_column_positions:
                     # If any diff has negative value, set all counter values to 0 and update cache
-                    if values[i] < old_values[i]:
+                    if int(values[i]) < int(old_values[i]):
                         has_negative_diff = True
                         break
 
                 if has_negative_diff:
                     for i in diff_column_positions:
-                        old_values[i] = 0
+                        old_values[i] = '0'
                         values[i] = ns_diff(values[i], old_values[i])
                     need_update_cache = True
                     continue

tests/flow_counter_stats_test.py

@@ -132,25 +132,25 @@ def test_diff(self):
         stats._collect = mock.MagicMock()
         old_data = {
             '': {
-                'bgp': [100, 200, 50.0, 1],
-                'bgpv6': [100, 200, 50.0, 2],
-                'lldp': [100, 200, 50.0, 3],
+                'bgp': ['100', '200', '50.0', '1'],
+                'bgpv6': ['100', '200', '50.0', '2'],
+                'lldp': ['100', '200', '50.0', '3'],
             }
         }
         stats._save(old_data)
         stats.data = {
             '': {
-                'bgp': [100, 200, 50.0, 4],
-                'bgpv6': [100, 100, 50.0, 2],
-                'lldp': [200, 300, 50.0, 3],
+                'bgp': ['100', '200', '50.0', '4'],
+                'bgpv6': ['100', '100', '50.0', '2'],
+                'lldp': ['200', '300', '50.0', '3'],
             }
         }
 
         stats._collect_and_diff()
         cached_data = stats._load()
-        assert cached_data['']['bgp'] == [0, 0, 50.0, 4]
-        assert cached_data['']['bgpv6'] == [0, 0, 50.0, 2]
-        assert cached_data['']['lldp'] == [100, 200, 50.0, 3]
+        assert cached_data['']['bgp'] == ['0', '0', '50.0', '4']
+        assert cached_data['']['bgpv6'] == ['0', '0', '50.0', '2']
+        assert cached_data['']['lldp'] == ['100', '200', '50.0', '3']
 
 
 class TestTrapStatsMultiAsic: