[BFN] Update psu.py to process sigterm signal (sonic-net#13350)

Why I did it
Sometime, SIGTERM processing by psud takes more then default 10sec (please see stopwaitsecs in http://supervisord.org/configuration.html).

Due to this, the following two testcases may fail:

test_pmon_psud_stop_and_start_status
test_pmon_psud_term_and_start_status
How I did it
Update PSU plugin to process sigterm signal so that psud runs faster to end last cycle in time

How to verify it
Run SONiC CTs:
test_pmon_psud_stop_and_start_status
test_pmon_psud_term_and_start_status

Author: dmytroxIntel

platform/barefoot/sonic-platform-modules-bfn-montara/sonic_platform/platform_utils.py

@@ -9,6 +9,8 @@
 except ImportError as e:
     raise ImportError(str(e) + "- required module not found")
 
+SIGTERM_CAUGHT = False
+
 def file_create(path, mode=None):
     """
     Ensure that file is created with the appropriate permissions
@@ -38,13 +40,16 @@ def wrapper(*args, **kwargs):
         def handler(sig, frame):
             if sigterm_handler:
                 sigterm_handler(sig, frame)
+                global SIGTERM_CAUGHT
+                SIGTERM_CAUGHT = True
             raise Exception("Canceling {}() execution...".format(func.__name__))
 
         sigterm_handler = signal.getsignal(signal.SIGTERM)
         signal.signal(signal.SIGTERM, handler)
         result = None
         try:
-            result = func(*args, **kwargs)
+            if not SIGTERM_CAUGHT:
+                result = func(*args, **kwargs)
         finally:
             signal.signal(signal.SIGTERM, sigterm_handler)
         return result

platform/barefoot/sonic-platform-modules-bfn-montara/sonic_platform/psu.py

@@ -28,6 +28,13 @@ class Psu(PsuBase):
     __sensors_info = None
     __timestamp = 0
 
+    # When psud gets termination signal it starts processing last cycle.
+    # This cycle must be as fast as possible to be able to stop correctly,
+    # otherwise it will be killed, so the whole plugin must encounter
+    # this signal to process operations based on state, where the
+    # state is "termination signal got" and "no termination signal"
+
+    # State is "no termination signal"
     sigterm = False
     sigterm_default_handler = None
     cls_inited = False
@@ -54,12 +61,15 @@ def signal_handler(cls, sig, frame):
         if cls.sigterm_default_handler:
             cls.sigterm_default_handler(sig, frame)
         syslog.syslog(syslog.LOG_INFO, "Canceling PSU platform API calls...")
+        # Changing state to "termination signal"
         cls.sigterm = True
 
     @classmethod
     def __sensors_get(cls, cached=True):
         cls.__lock.acquire()
-        if time.time() > cls.__timestamp + 15:
+        # Operation may take a few seconds to process, so if state is
+        # "termination signal", plugin doesn't perform this operation
+        if time.time() > cls.__timestamp + 15 and not Psu.sigterm:
             # Update cache once per 15 seconds
             try:
                 cls.__sensors_info = get_psu_metrics()
@@ -83,6 +93,8 @@ def __info_get(self):
         def psu_info_get(client):
             return client.pltfm_mgr.pltfm_mgr_pwr_supply_info_get(self.__index)
 
+        # Operation may take a few seconds to process, so if state is
+        # "termination signal", plugin doesn't perform this operation
         # Update cache once per 2 seconds
         if self.__ts + 2 < time.time() and not Psu.sigterm:
             self.__info = None
@@ -96,6 +108,10 @@ def psu_info_get(client):
                 return self.__info
         return self.__info
 
+    @cancel_on_sigterm
+    def get_metric_value(self, metric_name):
+        return get_metric_value(Psu.__sensors_get(), "PSU%d ".format(self.__index) + metric_name)
+
     @staticmethod
     def get_num_psus():
         """
@@ -127,7 +143,7 @@ def get_voltage(self):
             A float number, the output voltage in volts,
             e.g. 12.1
         """
-        return get_metric_value(Psu.__sensors_get(), "PSU%d 12V Output Voltage_in1_input" % self.__index)
+        return self.get_metric_value("12V Output Voltage_in1_input")
 
     def get_current(self):
         """
@@ -136,7 +152,7 @@ def get_current(self):
         Returns:
             A float number, the electric current in amperes, e.g 15.4
         """
-        return get_metric_value(Psu.__sensors_get(), "PSU%d 12V Output Current_curr2_input" % self.__index)
+        return self.get_metric_value("12V Output Current_curr2_input")
 
     def get_input_voltage(self):
         """
@@ -145,15 +161,15 @@ def get_input_voltage(self):
             A float number, the input voltage in volts,
             e.g. 220
         """
-        return get_metric_value(Psu.__sensors_get(), "PSU%d Input Voltage_in0_input" % self.__index)
+        return self.get_metric_value("Input Voltage_in0_input")
 
     def get_input_current(self):
         """
         Retrieves the input current draw of the power supply
         Returns:
             A float number, the electric current in amperes, e.g 0.8
         """
-        return get_metric_value(Psu.__sensors_get(), "PSU%d Input Current_curr1_input" % self.__index)
+        return self.get_metric_value("Input Current_curr1_input")
 
     def get_power(self):
         """
@@ -177,6 +193,9 @@ def psu_present_get(client):
             return client.pltfm_mgr.pltfm_mgr_pwr_supply_present_get(self.__index)
 
         status = False
+        if Psu.sigterm:
+            return status
+
         try:
             status = thrift_try(psu_present_get, attempts=1)
         except Exception as e:
@@ -267,22 +286,28 @@ def get_position_in_parent(self):
         """
         return self.__index
 
+    @cancel_on_sigterm
     def get_temperature(self):
         """
         Retrieves current temperature reading from PSU
         Returns:
             A float number of current temperature in Celsius up to nearest thousandth
             of one degree Celsius, e.g. 30.125
         """
+        # Operation may take a few seconds to process, so if state is
+        # "termination signal", plugin doesn't perform this operation
         return self.get_thermal(0).get_temperature()
 
+    @cancel_on_sigterm
     def get_temperature_high_threshold(self):
         """
         Retrieves the high threshold temperature of PSU
         Returns:
             A float number, the high threshold temperature of PSU in Celsius
             up to nearest thousandth of one degree Celsius, e.g. 30.125
         """
+        # Operation may take a few seconds to process, so if state is
+        # "termination signal", plugin doesn't perform this operation
         return self.get_thermal(0).get_high_threshold()
 
     @property