Update db_migrator to support PORT_QOS_MAP|global (#2205)

Signed-off-by: bingwang <wang.bing@microsoft.com>

What I did
This PR is to update the db_migrator to support generation of PORT_QOS_MAP|global.

After PR sonic-net/sonic-buildimage#10565, there will be two DSCP_TO_TC_MAP

DSCP_TO_TC_MAP|AZURE is the default map, which is used at port level and switch level
DSCP_TO_TC_MAP|AZURE_TUNNEL is used to remap the priority of tunnel traffic in dualtor deployment
To address the issue, an entry PORT_QOS_MAP|global will be added into config_db

"PORT_QOS_MAP": {
        "global": {
            "dscp_to_tc_map": "AZURE"
        }
}
To handle the upgrade from older image, db_migrator is updated to generate the entry.
There is no way to check if PORT_QOS_MAP|global is supported, so the migration is ran on all platforms. There is check in sonic-swss to check the switch capability code, so it will not cause issue.

How I did it
Update db_migrator to add a common migration step.

How to verify it
Verified by vstest

scripts/db_migrator.py

@@ -44,7 +44,7 @@ def __init__(self, namespace, socket=None):
                      none-zero values.
               build: sequentially increase within a minor version domain.
         """
-        self.CURRENT_VERSION = 'version_3_0_5'
+        self.CURRENT_VERSION = 'version_3_0_6'
 
         self.TABLE_NAME      = 'VERSIONS'
         self.TABLE_KEY       = 'DATABASE'
@@ -485,6 +485,23 @@ def migrate_qos_fieldval_reference_format(self):
         self.migrate_qos_db_fieldval_reference_remove(qos_table_list, self.configDB, self.configDB.CONFIG_DB, '|')
         return True
 
+    def migrate_port_qos_map_global(self):
+        """
+        Generate dscp_to_tc_map for switch.
+        """
+        asics_require_global_dscp_to_tc_map = ["broadcom"]
+        if self.asic_type not in asics_require_global_dscp_to_tc_map:
+            return
+        dscp_to_tc_map_table_names = self.configDB.get_keys('DSCP_TO_TC_MAP')
+        if len(dscp_to_tc_map_table_names) == 0:
+            return
+
+        qos_maps = self.configDB.get_table('PORT_QOS_MAP')
+        if 'global' not in qos_maps.keys():
+            # We are unlikely to have more than 1 DSCP_TO_TC_MAP in previous versions
+            self.configDB.set_entry('PORT_QOS_MAP', 'global', {"dscp_to_tc_map": dscp_to_tc_map_table_names[0]})
+            log.log_info("Created entry for global DSCP_TO_TC_MAP {}".format(dscp_to_tc_map_table_names[0]))
+
     def version_unknown(self):
         """
         version_unknown tracks all SONiC versions that doesn't have a version
@@ -681,9 +698,17 @@ def version_3_0_4(self):
 
     def version_3_0_5(self):
         """
-        Current latest version. Nothing to do here.
+        Version 3_0_5
         """
         log.log_info('Handling version_3_0_5')
+        self.migrate_port_qos_map_global()
+        return 'version_3_0_6'
+
+    def version_3_0_6(self):
+        """
+        Current latest version. Nothing to do here.
+        """
+        log.log_info('Handling version_3_0_6')
         return None
 
     def get_version(self):

tests/db_migrator_input/config_db/qos_map_table_global_expected.json

@@ -0,0 +1,12 @@
+{
+    "VERSIONS|DATABASE": {
+        "VERSION": "version_3_0_6"
+    },
+    "DSCP_TO_TC_MAP|AZURE": {
+        "0": "0",
+        "1": "1"
+    },
+    "PORT_QOS_MAP|global": {
+        "dscp_to_tc_map": "AZURE"
+    }
+}

tests/db_migrator_input/config_db/qos_map_table_global_input.json

@@ -0,0 +1,10 @@
+{
+    "VERSIONS|DATABASE": {
+        "VERSION": "version_3_0_5"
+    },
+    "DSCP_TO_TC_MAP|AZURE": {
+        "0": "0",
+        "1": "1"
+    }
+}
+

tests/db_migrator_test.py

@@ -374,3 +374,39 @@ def test_pfc_enable_migrator(self):
 
         diff = DeepDiff(resulting_table, expected_table, ignore_order=True)
         assert not diff
+
+class TestGlobalDscpToTcMapMigrator(object):
+    @classmethod
+    def setup_class(cls):
+        os.environ['UTILITIES_UNIT_TESTING'] = "2"
+
+    @classmethod
+    def teardown_class(cls):
+        os.environ['UTILITIES_UNIT_TESTING'] = "0"
+        dbconnector.dedicated_dbs['CONFIG_DB'] = None
+
+    def test_global_dscp_to_tc_map_migrator(self):
+        dbconnector.dedicated_dbs['CONFIG_DB'] = os.path.join(mock_db_path, 'config_db', 'qos_map_table_global_input')
+        import db_migrator
+        dbmgtr = db_migrator.DBMigrator(None)
+        dbmgtr.asic_type = "broadcom"
+        dbmgtr.hwsku = "vs"
+        dbmgtr.migrate()
+        dbconnector.dedicated_dbs['CONFIG_DB'] = os.path.join(mock_db_path, 'config_db', 'qos_map_table_global_expected')
+        expected_db = Db()
+
+        resulting_table = dbmgtr.configDB.get_table('PORT_QOS_MAP')
+        expected_table = expected_db.cfgdb.get_table('PORT_QOS_MAP')
+
+        diff = DeepDiff(resulting_table, expected_table, ignore_order=True)
+        assert not diff
+
+        # Check port_qos_map|global is not generated on mellanox asic
+        dbconnector.dedicated_dbs['CONFIG_DB'] = os.path.join(mock_db_path, 'config_db', 'qos_map_table_global_input')
+        dbmgtr_mlnx = db_migrator.DBMigrator(None)
+        dbmgtr_mlnx.asic_type = "mellanox"
+        dbmgtr_mlnx.hwsku = "vs"
+        dbmgtr_mlnx.migrate()
+        resulting_table = dbmgtr_mlnx.configDB.get_table('PORT_QOS_MAP')
+        assert resulting_table == {}
+