[psud] Refactor PSU object retrieval to improve exception handling

sonic-psud/scripts/psud

@@ -90,31 +90,65 @@ exit_code = 0
 # temporary wrappers that are compliable with both new platform api and old-style plugin mode
 
 
-def _wrapper_get_num_psus():
+def _wrapper_get_num_psus(logger):
     if platform_chassis is not None:
         try:
             return platform_chassis.get_num_psus()
         except NotImplementedError:
             pass
-    return platform_psuutil.get_num_psus()
+    if platform_psuutil is not None:
+        return platform_psuutil.get_num_psus()
+    return 0
 
 
-def _wrapper_get_psu_presence(psu_index):
+def _wrapper_get_psu(logger, psu_index):
+    """
+    Get PSU object from platform chassis
+    :param psu_index: PSU index (1-based)
+    :return: PSU object if available, None otherwise
+    """
     if platform_chassis is not None:
         try:
-            return platform_chassis.get_psu(psu_index - 1).get_presence()
-        except NotImplementedError:
-            pass
-    return platform_psuutil.get_psu_presence(psu_index)
+            return platform_chassis.get_psu(psu_index - 1)
+        except NotImplementedError as e:
+            if logger:
+                logger.log_warning("get_psu() not implemented by platform chassis: {}".format(str(e)))
+            return None
+        except Exception as e:
+            if logger:
+                logger.log_warning("Failed to get PSU {} from platform chassis: {}".format(psu_index, str(e)))
+            return None
+    return None
 
 
-def _wrapper_get_psu_status(psu_index):
+def _wrapper_get_psu_presence(logger, psu_index):
     if platform_chassis is not None:
-        try:
-            return platform_chassis.get_psu(psu_index - 1).get_powergood_status()
-        except NotImplementedError:
-            pass
-    return platform_psuutil.get_psu_status(psu_index)
+        psu = _wrapper_get_psu(logger, psu_index)
+        if psu:
+            try:
+                return psu.get_presence()
+            except NotImplementedError:
+                pass
+    if platform_psuutil is not None:
+        return platform_psuutil.get_psu_presence(psu_index)
+    if logger:
+        logger.log_error("Failed to get PSU {} presence".format(psu_index))
+    return False
+
+
+def _wrapper_get_psu_status(logger, psu_index):
+    if platform_chassis is not None:
+        psu = _wrapper_get_psu(logger, psu_index)
+        if psu:
+            try:
+                return psu.get_powergood_status()
+            except NotImplementedError:
+                pass
+    if platform_psuutil is not None:
+        return platform_psuutil.get_psu_status(psu_index)
+    if logger:
+        logger.log_error("Failed to get PSU {} status".format(psu_index))
+    return False
 
 
 #
@@ -123,13 +157,15 @@ def _wrapper_get_psu_status(psu_index):
 
 def get_psu_key(psu_index):
     if platform_chassis is not None:
-        try:
-            return platform_chassis.get_psu(psu_index - 1).get_name()
-        except NotImplementedError:
-            pass
-        except IndexError:
-            #some functionality is expectent on returning an expected key even if the psu object itself does not exist
-            pass
+        psu = _wrapper_get_psu(None, psu_index)
+        if psu:
+            try:
+                return psu.get_name()
+            except NotImplementedError:
+                pass
+            except IndexError:
+                #some functionality is expectent on returning an expected key even if the psu object itself does not exist
+                pass
     return PSU_INFO_KEY_TEMPLATE.format(psu_index)
 
 
@@ -398,8 +434,9 @@ class DaemonPsud(daemon_base.DaemonBase):
             try:
                 platform_psuutil = self.load_platform_util(PLATFORM_SPECIFIC_MODULE_NAME, PLATFORM_SPECIFIC_CLASS_NAME)
             except Exception as e:
-                self.log_error("Failed to load psuutil: %s" % (str(e)), True)
-                sys.exit(PSUUTIL_LOAD_ERROR)
+                self.log_warning("Failed to load psuutil: %s" % (str(e)), True)
+                # Don't expect the PSUD to exit just because psuutil is not available
+
 
         # Connect to STATE_DB and create psu/chassis info tables
         state_db = daemon_base.db_connect("STATE_DB")
@@ -409,7 +446,7 @@ class DaemonPsud(daemon_base.DaemonBase):
         self.phy_entity_tbl = swsscommon.Table(state_db, PHYSICAL_ENTITY_INFO_TABLE)
 
         # Post psu number info to STATE_DB
-        self.num_psus = _wrapper_get_num_psus()
+        self.num_psus = _wrapper_get_num_psus(self)
         fvs = swsscommon.FieldValuePairs([(CHASSIS_INFO_PSU_NUM_FIELD, str(self.num_psus))])
         self.chassis_tbl.set(CHASSIS_INFO_KEY, fvs)
 
@@ -474,7 +511,7 @@ class DaemonPsud(daemon_base.DaemonBase):
 
     def _update_single_psu_data(self, index, psu):
         name = get_psu_key(index)
-        presence = _wrapper_get_psu_presence(index)
+        presence = _wrapper_get_psu_presence(self, index)
         power_good = False
         voltage = NOT_AVAILABLE
         voltage_high_threshold = NOT_AVAILABLE
@@ -488,7 +525,7 @@ class DaemonPsud(daemon_base.DaemonBase):
         in_current = NOT_AVAILABLE
         max_power = NOT_AVAILABLE
         if presence:
-            power_good = _wrapper_get_psu_status(index)
+            power_good = _wrapper_get_psu_status(self, index)
             voltage = try_get(psu.get_voltage, NOT_AVAILABLE)
             voltage_high_threshold = try_get(psu.get_voltage_high_threshold, NOT_AVAILABLE)
             voltage_low_threshold = try_get(psu.get_voltage_low_threshold, NOT_AVAILABLE)
@@ -612,8 +649,8 @@ class DaemonPsud(daemon_base.DaemonBase):
              (PSU_INFO_IN_CURRENT_FIELD, str(in_current)),
              (PSU_INFO_IN_VOLTAGE_FIELD, str(in_voltage)),
              (PSU_INFO_POWER_MAX_FIELD, str(max_power)),
-             (PSU_INFO_PRESENCE_FIELD, 'true' if _wrapper_get_psu_presence(index) else 'false'),
-             (PSU_INFO_STATUS_FIELD, 'true' if _wrapper_get_psu_status(index) else 'false'),
+             (PSU_INFO_PRESENCE_FIELD, 'true' if _wrapper_get_psu_presence(self, index) else 'false'),
+             (PSU_INFO_STATUS_FIELD, 'true' if _wrapper_get_psu_status(self, index) else 'false'),
              ])
         self.psu_tbl.set(name, fvs)
 
@@ -642,7 +679,7 @@ class DaemonPsud(daemon_base.DaemonBase):
         :return:
         """
         psu_name = get_psu_key(psu_index)
-        presence = _wrapper_get_psu_presence(psu_index)
+        presence = _wrapper_get_psu_presence(self, psu_index)
         fan_list = psu.get_all_fans()
         for index, fan in enumerate(fan_list):
             fan_name = try_get(fan.get_name, '{} FAN {}'.format(psu_name, index + 1))