Handle the new db version which mellanox_buffer_migrator isn't intere…

…sted (sonic-net#1566)

Enhancement: handle the case that no buffer change in the latest database version
Current, the following two versions are the same:
- The latest version changed by mellanox_buffer_migrator
- The latest version in CONFIG_DB

That won't be true if another part in CONFIG_DB is updated. In that case, the latest version in CONFIG_DB will be greater than the latest version in mellanox_buffer_migrator.
However, this can break the buffer migrator unit test:
- The db_migrator will always migrate the database to the latest version
- The config database version check will fail in case the latest version in the config database doesn't match that defined in the buffer migrator.

This is to support this case.

Signed-off-by: Stephen Sun <stephens@nvidia.com>

tests/db_migrator_test.py

@@ -76,6 +76,16 @@ def check_appl_db(self, result, expected):
             for key in keys:
                 assert expected.get_all(expected.APPL_DB, key) == result.get_all(result.APPL_DB, key)
 
+    def advance_version_for_expected_database(self, migrated_db, expected_db):
+        # In case there are new db versions greater than the latest one that mellanox buffer migrator is interested,
+        # we just advance the database version in the expected database to make the test pass
+        expected_dbversion = expected_db.get_entry('VERSIONS', 'DATABASE')
+        dbmgtr_dbversion = migrated_db.get_entry('VERSIONS', 'DATABASE')
+        if expected_dbversion and dbmgtr_dbversion:
+            if expected_dbversion['VERSION'] == self.version_list[-1] and dbmgtr_dbversion['VERSION'] > expected_dbversion['VERSION']:
+                expected_dbversion['VERSION'] = dbmgtr_dbversion['VERSION']
+                expected_db.set_entry('VERSIONS', 'DATABASE', expected_dbversion)
+
     @pytest.mark.parametrize('scenario',
                              ['empty-config',
                               'non-default-config',
@@ -93,6 +103,7 @@ def test_mellanox_buffer_migrator_negative_cold_reboot(self, scenario):
         dbmgtr = db_migrator.DBMigrator(None)
         dbmgtr.migrate()
         expected_db = self.mock_dedicated_config_db(db_after_migrate)
+        self.advance_version_for_expected_database(dbmgtr.configDB, expected_db.cfgdb)
         self.check_config_db(dbmgtr.configDB, expected_db.cfgdb)
         assert not dbmgtr.mellanox_buffer_migrator.is_buffer_config_default
 
@@ -119,8 +130,6 @@ def test_mellanox_buffer_migrator_for_cold_reboot(self, sku_version, topo):
         sku, start_version = sku_version
         version = start_version
         start_index = self.version_list.index(start_version)
-        # Eventually, the config db should be migrated to the latest version
-        expected_db = self.mock_dedicated_config_db(self.make_db_name_by_sku_topo_version(sku, topo, self.version_list[-1]))
 
         # start_version represents the database version from which the SKU is supported
         # For each SKU,
@@ -130,6 +139,9 @@ def test_mellanox_buffer_migrator_for_cold_reboot(self, sku_version, topo):
             import db_migrator
             dbmgtr = db_migrator.DBMigrator(None)
             dbmgtr.migrate()
+            # Eventually, the config db should be migrated to the latest version
+            expected_db = self.mock_dedicated_config_db(self.make_db_name_by_sku_topo_version(sku, topo, self.version_list[-1]))
+            self.advance_version_for_expected_database(dbmgtr.configDB, expected_db.cfgdb)
             self.check_config_db(dbmgtr.configDB, expected_db.cfgdb)
             assert dbmgtr.mellanox_buffer_migrator.is_buffer_config_default
 
@@ -145,6 +157,7 @@ def mellanox_buffer_migrator_warm_reboot_runner(self, input_config_db, input_app
         import db_migrator
         dbmgtr = db_migrator.DBMigrator(None)
         dbmgtr.migrate()
+        self.advance_version_for_expected_database(dbmgtr.configDB, expected_config_db.cfgdb)
         assert dbmgtr.mellanox_buffer_migrator.is_buffer_config_default == is_buffer_config_default_expected
         self.check_config_db(dbmgtr.configDB, expected_config_db.cfgdb)
         self.check_appl_db(dbmgtr.appDB, expected_appl_db)
@@ -173,6 +186,7 @@ def test_mellanox_buffer_migrator_for_warm_reboot(self, sku, topo):
         self.mellanox_buffer_migrator_warm_reboot_runner(input_db_name, input_db_name, expected_db_name, expected_db_name, True)
 
     def test_mellanox_buffer_migrator_negative_nondefault_for_warm_reboot(self):
+        device_info.get_sonic_version_info = get_sonic_version_info_mlnx
         expected_config_db = 'non-default-config-expected'
         expected_appl_db = 'non-default-expected'
         input_config_db = 'non-default-config-input'