From 5d7b5cbb57d37011c591a618005189a21f08e254 Mon Sep 17 00:00:00 2001
From: Tom Hughes <tom@compton.nu>
Date: Sun, 14 Nov 2021 10:32:52 +0000
Subject: [PATCH] Add support for fan sensors which report as a percentage

Fan sensors on HP servers report speed as a percentage of the
maximum instead of a raw RPM value.

Signed-off-by: Tom Hughes <tom@compton.nu>
---
 collector_ipmi.go | 33 ++++++++++++++++++++++++---------
 docs/metrics.md   | 14 ++++++++++----
 2 files changed, 34 insertions(+), 13 deletions(-)

diff --git a/collector_ipmi.go b/collector_ipmi.go
index dfac986..11c9b90 100644
--- a/collector_ipmi.go
+++ b/collector_ipmi.go
@@ -42,13 +42,20 @@ var (
 		nil,
 	)
 
-	fanSpeedDesc = prometheus.NewDesc(
+	fanSpeedRPMDesc = prometheus.NewDesc(
 		prometheus.BuildFQName(namespace, "fan_speed", "rpm"),
 		"Fan speed in rotations per minute.",
 		[]string{"id", "name"},
 		nil,
 	)
 
+	fanSpeedRatioDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, "fan_speed", "ratio"),
+		"Fan speed as a proportion of the maximum speed.",
+		[]string{"id", "name"},
+		nil,
+	)
+
 	fanSpeedStateDesc = prometheus.NewDesc(
 		prometheus.BuildFQName(namespace, "fan_speed", "state"),
 		"Reported state of a fan speed sensor (0=nominal, 1=warning, 2=critical).",
@@ -162,15 +169,22 @@ func (c IPMICollector) Collect(result freeipmi.Result, ch chan<- prometheus.Metr
 
 		switch data.Unit {
 		case "RPM":
-			collectTypedSensor(ch, fanSpeedDesc, fanSpeedStateDesc, state, data)
+			collectTypedSensor(ch, fanSpeedRPMDesc, fanSpeedStateDesc, state, data, 1.0)
 		case "C":
-			collectTypedSensor(ch, temperatureDesc, temperatureStateDesc, state, data)
+			collectTypedSensor(ch, temperatureDesc, temperatureStateDesc, state, data, 1.0)
 		case "A":
-			collectTypedSensor(ch, currentDesc, currentStateDesc, state, data)
+			collectTypedSensor(ch, currentDesc, currentStateDesc, state, data, 1.0)
 		case "V":
-			collectTypedSensor(ch, voltageDesc, voltageStateDesc, state, data)
+			collectTypedSensor(ch, voltageDesc, voltageStateDesc, state, data, 1.0)
 		case "W":
-			collectTypedSensor(ch, powerDesc, powerStateDesc, state, data)
+			collectTypedSensor(ch, powerDesc, powerStateDesc, state, data, 1.0)
+		case "%":
+			switch data.Type {
+			case "Fan":
+				collectTypedSensor(ch, fanSpeedRatioDesc, fanSpeedStateDesc, state, data, 0.01)
+			default:
+				collectGenericSensor(ch, state, data)
+			}
 		default:
 			collectGenericSensor(ch, state, data)
 		}
@@ -181,7 +195,8 @@ func (c IPMICollector) Collect(result freeipmi.Result, ch chan<- prometheus.Metr
 func (c IPMICollector) Describe(ch chan<- *prometheus.Desc) {
 	ch <- sensorStateDesc
 	ch <- sensorValueDesc
-	ch <- fanSpeedDesc
+	ch <- fanSpeedRPMDesc
+	ch <- fanSpeedRatioDesc
 	ch <- fanSpeedStateDesc
 	ch <- temperatureDesc
 	ch <- temperatureStateDesc
@@ -193,11 +208,11 @@ func (c IPMICollector) Describe(ch chan<- *prometheus.Desc) {
 	ch <- powerStateDesc
 }
 
-func collectTypedSensor(ch chan<- prometheus.Metric, desc, stateDesc *prometheus.Desc, state float64, data freeipmi.SensorData) {
+func collectTypedSensor(ch chan<- prometheus.Metric, desc, stateDesc *prometheus.Desc, state float64, data freeipmi.SensorData, scale float64) {
 	ch <- prometheus.MustNewConstMetric(
 		desc,
 		prometheus.GaugeValue,
-		data.Value,
+		data.Value*scale,
 		strconv.FormatInt(data.ID, 10),
 		data.Name,
 	)
diff --git a/docs/metrics.md b/docs/metrics.md
index 48c45ce..8fcef3f 100644
--- a/docs/metrics.md
+++ b/docs/metrics.md
@@ -111,14 +111,20 @@ sensor ID and the sensor name as labels. Example:
 
 ### Fan speed sensors
 
-Fan speed sensors measure fan speed in rotations per minute (RPM) and their
-state usually reflects the speed being to low, indicating the fan might be
-broken. For each fan speed sensor, two metrics are exported (state and value),
-using the sensor ID and the sensor name as labels. Example:
+Fan speed sensors measure fan speed in rotations per minute (RPM) or as a
+percentage of the maximum speed, and their state usually reflects the speed
+being to low, indicating the fan might be broken. For each fan speed sensor,
+two metrics are exported (state and value), using the sensor ID and the
+sensor name as labels. Example:
 
     ipmi_fan_speed_rpm{id="12",name="Fan1A"} 4560
     ipmi_fan_speed_state{id="12",name="Fan1A"} 0
 
+or, for a percentage based fan:
+
+    ipmi_fan_speed_ratio{id="58",name="Fan 1 DutyCycle"} 0.2195
+    ipmi_fan_speed_state{id="58",name="Fan 1 DutyCycle"} 0
+
 ### Voltage sensors
 
 Voltage sensors measure a voltage in Volts. For each voltage sensor, two