Merge pull request vmware-archive#170 from KohliDev/handle-exception

Handling Exception

liota/entities/metrics/registered_metric.py

@@ -121,7 +121,10 @@ def send_data(self):
         if not self.values:
             # No values measured since last report_data
             return True
-        self.ref_dcc.publish(self)
+        try:
+            self.ref_dcc.publish(self)
+        except Exception:
+            log.error("Exception while publishing message", exc_info=True)
 
     def __str__(self, *args, **kwargs):
         return str(self.ref_entity.name) + ":" + str(self._next_run_time)

liota/lib/transports/mqtt.py

@@ -339,13 +339,11 @@ def publish(self, topic, message, qos, retain=False):
         :param retain: Message to be retained or not
         :return:
         """
-        # TODO: Retry logic to be designed
-        try:
-            mess_info = self._paho_client.publish(topic, message, qos, retain)
-            log.info("Publishing Message ID : {0} with result code : {1} ".format(mess_info.mid, mess_info.rc))
-            log.debug("Published Topic:{0}, Payload:{1}, QoS:{2}".format(topic, message, qos))
-        except Exception:
-            log.exception("MQTT Publish exception traceback..")
+        mess_info = self._paho_client.publish(topic, message, qos, retain)
+        if mess_info.rc == 0:
+            log.debug("Published Message ID:{0} with result code:{1}, Topic:{2}, Payload:{3}, QoS:{4}".format(mess_info.mid, mess_info.rc, topic, message, qos))
+        else:
+            raise Exception("MQTT Publish exception Message ID:{0} with result code:{1}, Topic:{2}, Payload:{3}, QoS:{4}".format(mess_info.mid, mess_info.rc, topic, message, qos))
 
     def subscribe(self, topic, qos, callback):
         """

packages/user_packages/README.md

@@ -23,3 +23,6 @@ Kindly include the unregister edge_system call in the clean up method required d
 
 This is a sample user package to publish the basic edge system stats which we believe are required to
 monitor the health status of the edge system from Pulse IoT Control Center.
+Optional mechanism: If the device raises an intermittent exception during metric collection process it will be required to be handled in the user code
+otherwise if an exception is thrown from user code the collection process will be stopped for that metric.
+If the None value is returned by User Defined Method(UDM) then metric value for that particular collector instance won't be published.

packages/user_packages/iotcc_mqtt.py

@@ -43,6 +43,7 @@ class PackageClass(LiotaPackage):
 
     def run(self, registry):
         import copy
+        import time
         from liota.lib.utilities.identity import Identity
         from liota.dccs.iotcc import IotControlCenter
         from liota.dcc_comms.mqtt_dcc_comms import MqttDccComms
@@ -79,7 +80,19 @@ def run(self, registry):
             self.iotcc.set_system_properties(self.iotcc_edge_system, registry.get("system_properties"))
             # Set the properties for edge system as key:value pair, you can also set the location
             # by passing the latitude and longitude as a property in the user package
-            self.iotcc.set_properties(self.iotcc_edge_system,{"key1": "value1", "key2": "value2"})
+            # If the set_properties or register call fails due to DCC_Comms Publish exception
+            # the optional retry mechanism can be implemented in the following way
+            attempts = 0
+            while attempts < 3:
+                try:
+                    # Register edge system (gateway)
+                    self.iotcc.set_properties(self.iotcc_edge_system, {"key1": "value1", "key2": "value2"})
+                    break
+                except Exception:
+                    attempts += 1
+                    # The sleep time before re-trying depends on the infrastructure requirement of broker to restart
+                    # It can be modified or removed as per the infrastructure requirement
+                    time.sleep(5)
             registry.register("iotcc_mqtt", self.iotcc)
             # Store the registered edge system object in liota package manager registry after the
             # system properties are set for it

packages/user_packages/iotcc_mqtt_edge_system_stats.py

@@ -65,7 +65,15 @@ def read_cpu_utilization(sample_duration_sec=1):
 
 
 def read_disk_usage_stats():
-    return round(disk_stat.disk_reads_writes(disk_name)[0], 2)
+    # If the device raises an intermittent exception during metric collection process it will be required
+    # to be handled in the user code otherwise if an exception is thrown from user code
+    # the collection process will be stopped for that metric.
+    # If the None value is returned by UDM then metric value for that particular collector instance won't be published.
+    try:
+        disk_stat_value = round(disk_stat.disk_reads_writes(disk_name)[0], 2)
+    except Exception:
+        return None
+    return disk_stat_value
 
 
 def read_network_bytes_received():