Add a scaling factor (#1026)

Allow the metric value to be pre-scaled based on a float64 multiplier.
This allows for simple unit conversions like bits to bytes,
centi-degrees, etc.

Fixes: #734

Signed-off-by: SuperQ <[email protected]>

.gitignore

@@ -31,3 +31,4 @@ dependencies-stamp
 
 generator/generator
 generator/mibs
+generator/snmp.yml

collector/collector.go

@@ -607,6 +607,10 @@ func pduToSamples(indexOids []int, pdu *gosnmp.SnmpPDU, metric *config.Metric, o
 		}
 	}
 
+	if metric.Scale != 0.0 {
+		value *= metric.Scale
+	}
+
 	sample, err := prometheus.NewConstMetric(prometheus.NewDesc(metric.Name, metric.Help, labelnames, nil),
 		t, value, labelvalues...)
 	if err != nil {

collector/collector_test.go

@@ -231,6 +231,23 @@ func TestPduToSample(t *testing.T) {
 			oidToPdu:        make(map[string]gosnmp.SnmpPDU),
 			expectedMetrics: []string{`Desc{fqName: "test_metric", help: "Help string", constLabels: {}, variableLabels: []} gauge:{value:2}`},
 		},
+		{
+			pdu: &gosnmp.SnmpPDU{
+				Name:  "1.1.1.1.1",
+				Type:  gosnmp.Integer,
+				Value: 420,
+			},
+			indexOids: []int{},
+			metric: &config.Metric{
+				Name:  "test_metric",
+				Oid:   "1.1.1.1.1",
+				Type:  "gauge",
+				Help:  "Help string",
+				Scale: 0.1,
+			},
+			oidToPdu:        make(map[string]gosnmp.SnmpPDU),
+			expectedMetrics: []string{`Desc{fqName: "test_metric", help: "Help string", constLabels: {}, variableLabels: []} gauge:{value:42}`},
+		},
 		{
 			pdu: &gosnmp.SnmpPDU{
 				Name:  "1.1.1.1.1",

config/config.go

@@ -191,6 +191,7 @@ type Metric struct {
 	Lookups        []*Lookup                  `yaml:"lookups,omitempty"`
 	RegexpExtracts map[string][]RegexpExtract `yaml:"regex_extracts,omitempty"`
 	EnumValues     map[int]string             `yaml:"enum_values,omitempty"`
+	Scale          float64                    `yaml:"scale,omitempty"`
 }
 
 type Index struct {

generator/FORMAT.md

@@ -62,6 +62,7 @@ modules:
          Temp: # A new metric will be created appending this to the metricName to become metricNameTemp.
            - regex: '(.*)' # Regex to extract a value from the returned SNMP walks's value.
              value: '$1' # Parsed as float64, defaults to $1.
+       scale: 0.125 # Scale the sample by this value, for example bits to bytes.
        enum_values: # Enum for this metric. Only used with the enum types.
           0: true
           1: false

generator/README.md

@@ -146,6 +146,7 @@ modules:
               value: '1' # The first entry whose regex matches and whose value parses wins.
             - regex: '.*'
               value: '0'
+        scale: 1.0 # Scale the value of the sample by this value.
         type: DisplayString # Override the metric type, possible types are:
                              #   gauge:   An integer with type gauge.
                              #   counter: An integer with type counter.

generator/config.go

@@ -29,6 +29,7 @@ type Config struct {
 type MetricOverrides struct {
 	Ignore         bool                              `yaml:"ignore,omitempty"`
 	RegexpExtracts map[string][]config.RegexpExtract `yaml:"regex_extracts,omitempty"`
+	Scale          float64                           `yaml:"scale,omitempty"`
 	Type           string                            `yaml:"type,omitempty"`
 }
 

generator/generator.yml

@@ -154,6 +154,10 @@ modules:
         lookup: st4AdcSensorName
         drop_source_indexes: true
 
+    overrides:
+      st4TempSensorValue:
+        scale: 0.1
+
 # Palo Alto Firewalls
 #
 # Palo Alto MIBs can be found here:

generator/tree.go

@@ -502,6 +502,7 @@ func generateConfigModule(cfg *ModuleConfig, node *Node, nameToNode map[string]*
 		for _, metric := range out.Metrics {
 			if name == metric.Name || name == metric.Oid {
 				metric.RegexpExtracts = params.RegexpExtracts
+				metric.Scale = params.Scale
 			}
 		}
 	}

snmp.yml

@@ -23225,6 +23225,7 @@ modules:
         labelname: st4UnitName
         oid: 1.3.6.1.4.1.1718.4.1.2.2.1.3
         type: DisplayString
+      scale: 0.1
     - name: st4TempSensorStatus
       oid: 1.3.6.1.4.1.1718.4.1.9.3.1.2
       type: gauge