Fix: No explicit reading ConfigDB in get_asic_conf_file_path() (#10723)

#### Why I did it
This function is critical for is_multi_asic() and SonicDBConfig initializing. No explicit reading ConfigDB. Otherwise it will implicitly trigger SonicDBConfig initializing.

#### How I did it
1. No explicit reading ConfigDB in get_asic_conf_file_path()
2. Collect asic_conf_path_candidates lazily to prevent any unnecessary side effect and improve the performance

src/sonic-py-common/sonic_py_common/device_info.py

@@ -40,9 +40,10 @@ CHASSIS_INFO_SERIAL_FIELD = 'serial'
 CHASSIS_INFO_MODEL_FIELD = 'model'
 CHASSIS_INFO_REV_FIELD = 'revision'
 
-
-def get_localhost_info(field):
+def get_localhost_info(field, config_db=None):
     try:
+        # TODO: enforce caller to provide config_db explicitly and remove its default value
+        if not config_db:
             config_db = ConfigDBConnector()
             config_db.connect()
 
@@ -81,11 +82,16 @@ def get_machine_info():
 
     return machine_vars
 
-
-def get_platform():
+def get_platform(**kwargs):
     """
     Retrieve the device's platform identifier
 
+    Args:
+        config_db: a connected ConfigDBConector object.
+            If explicit None provided, this function will not read ConfigDB. This is useful before SonicDBConfig initializing.
+            If not provided, this function may implicitly ready ConfigDB.
+            Otherwise, this function will use it to read ConfigDB
+
     Returns:
         A string containing the device's platform identifier
     """
@@ -111,8 +117,13 @@ def get_platform():
     # container in SONiC, where the /host directory is not mounted. In this
     # case the value should already be populated in Config DB so we finally
     # try reading it from there.
-
-    return get_localhost_info('platform')
+    if 'config_db' in kwargs:
+        config_db = kwargs['config_db']
+        if config_db is None:
+            return None
+    else:
+        config_db = None
+    return get_localhost_info('platform', config_db=config_db)
 
 
 def get_hwsku():
@@ -144,21 +155,22 @@ def get_platform_and_hwsku():
 
 def get_asic_conf_file_path():
     """
-    Retrieves the path to the ASIC conguration file on the device
+    Retrieves the path to the ASIC configuration file on the device
 
     Returns:
-        A string containing the path to the ASIC conguration file on success,
+        A string containing the path to the ASIC configuration file on success,
         None on failure
     """
-    asic_conf_path_candidates = []
+    def asic_conf_path_candidates():
+        yield os.path.join(CONTAINER_PLATFORM_PATH, ASIC_CONF_FILENAME)
 
-    asic_conf_path_candidates.append(os.path.join(CONTAINER_PLATFORM_PATH, ASIC_CONF_FILENAME))
-
-    platform = get_platform()
+        # Note: this function is critical for is_multi_asic() and SonicDBConfig initializing
+        #   No explicit reading ConfigDB
+        platform = get_platform(config_db=None)
         if platform:
-        asic_conf_path_candidates.append(os.path.join(HOST_DEVICE_PATH, platform, ASIC_CONF_FILENAME))
+            yield os.path.join(HOST_DEVICE_PATH, platform, ASIC_CONF_FILENAME)
 
-    for asic_conf_file_path in asic_conf_path_candidates:
+    for asic_conf_file_path in asic_conf_path_candidates():
         if os.path.isfile(asic_conf_file_path):
             return asic_conf_file_path
 
@@ -167,10 +179,10 @@ def get_asic_conf_file_path():
 
 def get_platform_env_conf_file_path():
     """
-    Retrieves the path to the PLATFORM ENV conguration file on the device
+    Retrieves the path to the PLATFORM ENV configuration file on the device
 
     Returns:
-        A string containing the path to the PLATFORM ENV conguration file on success,
+        A string containing the path to the PLATFORM ENV configuration file on success,
         None on failure
     """
     platform_env_conf_path_candidates = []
@@ -339,7 +351,7 @@ def get_sonic_version_file():
 
 
 # Get hardware information
-def get_platform_info():
+def get_platform_info(config_db=None):
     """
     This function is used to get the HW info helper function
     """
@@ -356,6 +368,8 @@ def get_platform_info():
     hw_info_dict['asic_count'] = get_num_asics()
 
     try:
+        # TODO: enforce caller to provide config_db explicitly and remove its default value
+        if not config_db:
             config_db = ConfigDBConnector()
             config_db.connect()
 
@@ -462,7 +476,7 @@ def get_namespaces():
     return natsorted(ns_list)
 
 
-def get_all_namespaces():
+def get_all_namespaces(config_db=None):
     """
     In case of Multi-Asic platform, Each ASIC will have a linux network namespace created.
     So we loop through the databases in different namespaces and depending on the sub_role
@@ -476,6 +490,8 @@ def get_all_namespaces():
     if is_multi_npu():
         for npu in range(num_npus):
             namespace = "{}{}".format(NPU_NAME_PREFIX, npu)
+            # TODO: enforce caller to provide config_db explicitly and remove its default value
+            if not config_db:
                 config_db = ConfigDBConnector(use_unix_socket_path=True, namespace=namespace)
                 config_db.connect()
 

src/sonic-py-common/sonic_py_common/multi_asic.py

@@ -5,11 +5,8 @@ import subprocess
 from natsort import natsorted
 from swsscommon import swsscommon
 
-from .device_info import CONTAINER_PLATFORM_PATH
-from .device_info import HOST_DEVICE_PATH
-from .device_info import get_platform
-from .device_info import is_supervisor
-from .device_info import is_chassis
+from .device_info import get_asic_conf_file_path
+from .device_info import is_supervisor, is_chassis
 
 ASIC_NAME_PREFIX = 'asic'
 NAMESPACE_PATH_GLOB = '/run/netns/*'
@@ -78,32 +75,6 @@ def connect_to_all_dbs_for_ns(namespace=DEFAULT_NAMESPACE):
         db.connect(db_id)
     return db
 
-
-def get_asic_conf_file_path():
-    """
-    Retrieves the path to the ASIC conguration file on the device
-
-    Returns:
-        A string containing the path to the ASIC conguration file on success,
-        None on failure
-    """
-    asic_conf_path_candidates = []
-
-    asic_conf_path_candidates.append(os.path.join(CONTAINER_PLATFORM_PATH,
-                                                  ASIC_CONF_FILENAME))
-
-    platform = get_platform()
-    if platform:
-        asic_conf_path_candidates.append(os.path.join(
-            HOST_DEVICE_PATH, platform, ASIC_CONF_FILENAME))
-
-    for asic_conf_file_path in asic_conf_path_candidates:
-        if os.path.isfile(asic_conf_file_path):
-            return asic_conf_file_path
-
-    return None
-
-
 def get_num_asics():
     """
     Retrieves the num of asics present in the multi ASIC platform