Fix: initialize SonicDBConfig differently for single or multi_asic (continued) (#1417)

**- What I did**
This bug is exposed by #1392. Previously the `config` command will call `SonicDBConfig.load_sonic_global_db_config()` even on a single ASIC platform, and it will silently failed. After exposed, it will fail with error syslog message:
```
Feb  9 05:04:46.462361 vlab-01 ERR python3: :- initializeGlobalConfig: Sonic database config global file doesn't exist at /var/run/redis/sonic-db/database_global.json
```

**- How to verify it**
Unit test and test in DUT.

Author: qiluo-msft

acl_loader/main.py

@@ -9,7 +9,7 @@
 import tabulate
 import pyangbind.lib.pybindJSON as pybindJSON
 from natsort import natsorted
-from sonic_py_common import device_info
+from sonic_py_common import device_info, multi_asic
 from swsscommon.swsscommon import SonicV2Connector, ConfigDBConnector, SonicDBConfig
 
 
@@ -114,8 +114,13 @@ def __init__(self):
         self.tables_db_info = {}
         self.rules_db_info = {}
         self.rules_info = {}
-        # Load global db config. This call is no-op in single npu platforms
-        SonicDBConfig.load_sonic_global_db_config()
+
+        if multi_asic.is_multi_asic():
+            # Load global db config
+            SonicDBConfig.load_sonic_global_db_config()
+        else:
+            SonicDBConfig.initialize()
+
         self.sessions_db_info = {}
         self.configdb = ConfigDBConnector()
         self.configdb.connect()

crm/main.py

@@ -211,15 +211,20 @@ def cli(ctx):
     # Use the db object if given as input.
     db = None if ctx.obj is None else ctx.obj.cfgdb
 
+    # Note: SonicDBConfig may be already initialized in unit test, then skip
+    if not SonicDBConfig.isInit():
+        if multi_asic.is_multi_asic():
+            # Load the global config file database_global.json once.
+            SonicDBConfig.load_sonic_global_db_config()
+        else:
+            SonicDBConfig.initialize()
+
     context = {
         "crm": Crm(db)
     }
 
     ctx.obj = context
 
-    # Load the global config file database_global.json once.
-    SonicDBConfig.load_sonic_global_db_config()
-
 @cli.group()
 @click.pass_context
 def config(ctx):

scripts/db_migrator.py

@@ -555,6 +555,8 @@ def main():
 
         if args.namespace is not None:
             SonicDBConfig.load_sonic_global_db_config(namespace=args.namespace)
+        else:
+            SonicDBConfig.initialize()
 
         if socket_path:
             dbmgtr = DBMigrator(namespace, socket=socket_path)

scripts/lldpshow

@@ -25,7 +25,7 @@ import subprocess
 import sys
 import xml.etree.ElementTree as ET
 
-from sonic_py_common import device_info
+from sonic_py_common import device_info, multi_asic
 from swsscommon.swsscommon import ConfigDBConnector, SonicDBConfig
 from tabulate import tabulate
 
@@ -47,7 +47,11 @@ class Lldpshow(object):
         # So far only find Router and Bridge two capabilities in lldpctl, so any other capacility types will be read as Other
         # if further capability type is supported like WLAN, can just add the tag definition here
         self.ctags = {'Router': 'R', 'Bridge': 'B'}
-        SonicDBConfig.load_sonic_global_db_config()
+
+        if multi_asic.is_multi_asic():
+            SonicDBConfig.load_sonic_global_db_config()
+        else:
+            SonicDBConfig.initialize()
 
         # For multi-asic platforms we will get only front-panel interface to display
         namespaces = device_info.get_all_namespaces()

scripts/portconfig

@@ -82,6 +82,8 @@ def main():
 
     if args.namespace is not None:
         SonicDBConfig.load_sonic_global_db_config(namespace=args.namespace)
+    else:
+        SonicDBConfig.initialize()
 
     try:
         port = portconfig(args.verbose, args.port, args.namespace)