From f1e43b2593636f837ed0351cbd0d872db5655351 Mon Sep 17 00:00:00 2001
From: henrygd <hank@henrygd.me>
Date: Mon, 26 May 2025 01:08:03 -0400
Subject: [PATCH] scale fractional temperature values to reasonable Celsius
 values (#688)

---
 beszel/internal/agent/sensors.go      | 20 +++++++
 beszel/internal/agent/sensors_test.go | 82 +++++++++++++++++++++++++++
 2 files changed, 102 insertions(+)

diff --git a/beszel/internal/agent/sensors.go b/beszel/internal/agent/sensors.go
index a82bf69..384bccc 100644
--- a/beszel/internal/agent/sensors.go
+++ b/beszel/internal/agent/sensors.go
@@ -89,6 +89,10 @@ func (a *Agent) updateTemperatures(systemStats *system.Stats) {
 
 	systemStats.Temperatures = make(map[string]float64, len(temps))
 	for i, sensor := range temps {
+		// scale temperature
+		if sensor.Temperature != 0 && sensor.Temperature < 1 {
+			sensor.Temperature = scaleTemperature(sensor.Temperature)
+		}
 		// skip if temperature is unreasonable
 		if sensor.Temperature <= 0 || sensor.Temperature >= 200 {
 			continue
@@ -141,3 +145,19 @@ func isValidSensor(sensorName string, config *SensorConfig) bool {
 
 	return config.isBlacklist
 }
+
+// scaleTemperature scales temperatures in fractional values to reasonable Celsius values
+func scaleTemperature(temp float64) float64 {
+	if temp > 1 {
+		return temp
+	}
+	scaled100 := temp * 100
+	scaled1000 := temp * 1000
+
+	if scaled100 >= 15 && scaled100 <= 95 {
+		return scaled100
+	} else if scaled1000 >= 15 && scaled1000 <= 95 {
+		return scaled1000
+	}
+	return scaled100
+}
diff --git a/beszel/internal/agent/sensors_test.go b/beszel/internal/agent/sensors_test.go
index 22e1a5c..85970ac 100644
--- a/beszel/internal/agent/sensors_test.go
+++ b/beszel/internal/agent/sensors_test.go
@@ -372,3 +372,85 @@ func TestNewSensorConfig(t *testing.T) {
 	require.True(t, ok, "EnvMap should contain HostSysEnvKey")
 	assert.Equal(t, "/test/path", sysPath)
 }
+
+func TestScaleTemperature(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    float64
+		expected float64
+		desc     string
+	}{
+		// Normal temperatures (no scaling needed)
+		{"normal_cpu_temp", 45.0, 45.0, "Normal CPU temperature"},
+		{"normal_room_temp", 25.0, 25.0, "Normal room temperature"},
+		{"high_cpu_temp", 85.0, 85.0, "High CPU temperature"},
+		// Zero temperature
+		{"zero_temp", 0.0, 0.0, "Zero temperature"},
+		// Fractional values that should use 100x scaling
+		{"fractional_45c", 0.45, 45.0, "0.45 should become 45°C (100x)"},
+		{"fractional_25c", 0.25, 25.0, "0.25 should become 25°C (100x)"},
+		{"fractional_60c", 0.60, 60.0, "0.60 should become 60°C (100x)"},
+		{"fractional_75c", 0.75, 75.0, "0.75 should become 75°C (100x)"},
+		{"fractional_30c", 0.30, 30.0, "0.30 should become 30°C (100x)"},
+		// Fractional values that should use 1000x scaling
+		{"millifractional_45c", 0.045, 45.0, "0.045 should become 45°C (1000x)"},
+		{"millifractional_25c", 0.025, 25.0, "0.025 should become 25°C (1000x)"},
+		{"millifractional_60c", 0.060, 60.0, "0.060 should become 60°C (1000x)"},
+		{"millifractional_75c", 0.075, 75.0, "0.075 should become 75°C (1000x)"},
+		{"millifractional_35c", 0.035, 35.0, "0.035 should become 35°C (1000x)"},
+		// Edge cases - values outside reasonable range
+		{"very_low_fractional", 0.01, 1.0, "0.01 should default to 100x scaling (1°C)"},
+		{"very_high_fractional", 0.99, 99.0, "0.99 should default to 100x scaling (99°C)"},
+		{"extremely_low", 0.001, 0.1, "0.001 should default to 100x scaling (0.1°C)"},
+		// Boundary cases around the reasonable range (15-95°C)
+		{"boundary_low_100x", 0.15, 15.0, "0.15 should use 100x scaling (15°C)"},
+		{"boundary_high_100x", 0.95, 95.0, "0.95 should use 100x scaling (95°C)"},
+		{"boundary_low_1000x", 0.015, 15.0, "0.015 should use 1000x scaling (15°C)"},
+		{"boundary_high_1000x", 0.095, 95.0, "0.095 should use 1000x scaling (95°C)"},
+		// Values just outside reasonable range
+		{"just_below_range_100x", 0.14, 14.0, "0.14 should default to 100x (14°C)"},
+		{"just_above_range_100x", 0.96, 96.0, "0.96 should default to 100x (96°C)"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := scaleTemperature(tt.input)
+			assert.InDelta(t, tt.expected, result, 0.001,
+				"scaleTemperature(%v) = %v, expected %v (%s)",
+				tt.input, result, tt.expected, tt.desc)
+		})
+	}
+}
+
+func TestScaleTemperatureLogic(t *testing.T) {
+	// Test the logic flow for ambiguous cases
+	t.Run("prefers_100x_when_both_valid", func(t *testing.T) {
+		// 0.5 could be 50°C (100x) or 500°C (1000x)
+		// Should prefer 100x since it's tried first and is in range
+		result := scaleTemperature(0.5)
+		expected := 50.0
+		assert.InDelta(t, expected, result, 0.001,
+			"scaleTemperature(0.5) = %v, expected %v (should prefer 100x scaling)",
+			result, expected)
+	})
+
+	t.Run("uses_1000x_when_100x_too_low", func(t *testing.T) {
+		// 0.05 -> 5°C (100x, too low) or 50°C (1000x, in range)
+		// Should use 1000x since 100x is below reasonable range
+		result := scaleTemperature(0.05)
+		expected := 50.0
+		assert.InDelta(t, expected, result, 0.001,
+			"scaleTemperature(0.05) = %v, expected %v (should use 1000x scaling)",
+			result, expected)
+	})
+
+	t.Run("defaults_to_100x_when_both_invalid", func(t *testing.T) {
+		// 0.005 -> 0.5°C (100x, too low) or 5°C (1000x, too low)
+		// Should default to 100x scaling
+		result := scaleTemperature(0.005)
+		expected := 0.5
+		assert.InDelta(t, expected, result, 0.001,
+			"scaleTemperature(0.005) = %v, expected %v (should default to 100x)",
+			result, expected)
+	})
+}