Set Prometheus metric to 0 if SNMP metric not found (#121)

Author: evanugarte

collector/server.py

@@ -73,15 +73,6 @@ def work(ip_list):
 
 def get_snmp_data(ip):
     for oid in SnmpOid:
-        # set the error to zero by default, this is because
-        # SNMP OIDs related to errors often dissappear when
-        # the associated issue that the metric refers to is
-        # no longer present (i.e. an empty tray now has
-        # paper). To avoid leaving an error metric as 1
-        # which would create a false positive, set the error
-        # as zero before reading anything.
-        if oid.is_error:
-            snmp_error.labels(name=oid.metric_name, ip=ip).set(0)
         with snmp_req_duration.time():
             errorIndication, errorStatus, errorIndex, varBinds = next(
             getCmd(SnmpEngine(),
@@ -90,22 +81,30 @@ def get_snmp_data(ip):
             ContextData(),
             ObjectType(ObjectIdentity(oid.metric_value)))
             )
-            if errorIndication:
-                logging.error(f"Error indication from {ip} for metric {oid.metric_value}: {errorIndication}")
-                device_unreachable.set(1)
-                continue
-            if errorStatus:
-                logging.error(f"Error status from {ip} for metric {oid.metric_value}: {errorStatus.prettyPrint()}")
-                continue
-
-            device_unreachable.set(0)
-            if not varBinds:
-                continue
-            res = varBinds[0]
+        if errorIndication:
+            logging.error(f"Error indication from {ip} for metric {oid.metric_value}: {errorIndication}")
+            device_unreachable.set(1)
+            continue
+        if errorStatus:
+            logging.error(f"Error status from {ip} for metric {oid.metric_value}: {errorStatus.prettyPrint()}")
+            # SNMP OIDs related to errors often dissappear when
+            # the associated issue that the metric refers to is
+            # no longer present (i.e. an empty tray now has
+            # paper). To avoid leaving an error metric as 1
+            # which would create a false positive, set the metric
+            # to zero if the associated SNMP OID was not found
             if oid.is_error:
-              snmp_error.labels(name=oid.metric_name, ip=ip).set(1)
-              continue
-            snmp_metric.labels(name=oid.metric_name, ip=ip).set(res[1])
+                snmp_error.labels(name=oid.metric_name, ip=ip).set(0)
+            continue
+
+        device_unreachable.set(0)
+        if not varBinds:
+            continue
+        res = varBinds[0]
+        if oid.is_error:
+            snmp_error.labels(name=oid.metric_name, ip=ip).set(1)
+            continue
+        snmp_metric.labels(name=oid.metric_name, ip=ip).set(res[1])
 
 @app.get("/metrics")
 async def metrics():