From ad21cab457ef963543f519636b44a3c978380ef5 Mon Sep 17 00:00:00 2001
From: Jim Haff <Jimmyhaff3@gmail.com>
Date: Thu, 26 Mar 2026 19:03:51 -0500
Subject: [PATCH] Prevent temperature collection from blocking agent stats
 (#1839)

---
 agent/sensors.go      | 33 ++++++++++++++++++++--
 agent/sensors_test.go | 64 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 95 insertions(+), 2 deletions(-)

diff --git a/agent/sensors.go b/agent/sensors.go
index 08cd29dd..e4c0e7c9 100644
--- a/agent/sensors.go
+++ b/agent/sensors.go
@@ -2,12 +2,14 @@ package agent
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"log/slog"
 	"path"
 	"runtime"
 	"strconv"
 	"strings"
+	"time"
 	"unicode/utf8"
 
 	"github.com/henrygd/beszel/agent/utils"
@@ -38,6 +40,11 @@ func (a *Agent) newSensorConfig() *SensorConfig {
 // Matches sensors.TemperaturesWithContext to allow for panic recovery (gopsutil/issues/1832)
 type getTempsFn func(ctx context.Context) ([]sensors.TemperatureStat, error)
 
+var (
+	errTemperatureFetchTimeout = errors.New("temperature collection timed out")
+	temperatureFetchTimeout    = 2 * time.Second
+)
+
 // newSensorConfigWithEnv creates a SensorConfig with the provided environment variables
 // sensorsSet indicates if the SENSORS environment variable was explicitly set (even to empty string)
 func (a *Agent) newSensorConfigWithEnv(primarySensor, sysSensors, sensorsEnvVal string, skipCollection bool) *SensorConfig {
@@ -86,10 +93,12 @@ func (a *Agent) updateTemperatures(systemStats *system.Stats) {
 	// reset high temp
 	a.systemInfo.DashboardTemp = 0
 
-	temps, err := a.getTempsWithPanicRecovery(getSensorTemps)
+	temps, err := a.getTempsWithTimeout(getSensorTemps)
 	if err != nil {
 		// retry once on panic (gopsutil/issues/1832)
-		temps, err = a.getTempsWithPanicRecovery(getSensorTemps)
+		if !errors.Is(err, errTemperatureFetchTimeout) {
+			temps, err = a.getTempsWithTimeout(getSensorTemps)
+		}
 		if err != nil {
 			slog.Warn("Error updating temperatures", "err", err)
 			if len(systemStats.Temperatures) > 0 {
@@ -152,6 +161,26 @@ func (a *Agent) getTempsWithPanicRecovery(getTemps getTempsFn) (temps []sensors.
 	return
 }
 
+func (a *Agent) getTempsWithTimeout(getTemps getTempsFn) ([]sensors.TemperatureStat, error) {
+	type result struct {
+		temps []sensors.TemperatureStat
+		err   error
+	}
+
+	resultCh := make(chan result, 1)
+	go func() {
+		temps, err := a.getTempsWithPanicRecovery(getTemps)
+		resultCh <- result{temps: temps, err: err}
+	}()
+
+	select {
+	case res := <-resultCh:
+		return res.temps, res.err
+	case <-time.After(temperatureFetchTimeout):
+		return nil, errTemperatureFetchTimeout
+	}
+}
+
 // isValidSensor checks if a sensor is valid based on the sensor name and the sensor config
 func isValidSensor(sensorName string, config *SensorConfig) bool {
 	// if no sensors configured, everything is valid
diff --git a/agent/sensors_test.go b/agent/sensors_test.go
index de27ca35..23e2db6a 100644
--- a/agent/sensors_test.go
+++ b/agent/sensors_test.go
@@ -6,6 +6,7 @@ import (
 	"context"
 	"fmt"
 	"testing"
+	"time"
 
 	"github.com/henrygd/beszel/internal/entities/system"
 
@@ -526,3 +527,66 @@ func TestGetTempsWithPanicRecovery(t *testing.T) {
 		})
 	}
 }
+
+func TestGetTempsWithTimeout(t *testing.T) {
+	agent := &Agent{
+		sensorConfig: &SensorConfig{
+			context: context.Background(),
+		},
+	}
+
+	originalTimeout := temperatureFetchTimeout
+	t.Cleanup(func() {
+		temperatureFetchTimeout = originalTimeout
+	})
+	temperatureFetchTimeout = 10 * time.Millisecond
+
+	t.Run("returns temperatures before timeout", func(t *testing.T) {
+		temps, err := agent.getTempsWithTimeout(func(ctx context.Context) ([]sensors.TemperatureStat, error) {
+			return []sensors.TemperatureStat{{SensorKey: "cpu_temp", Temperature: 42}}, nil
+		})
+
+		require.NoError(t, err)
+		require.Len(t, temps, 1)
+		assert.Equal(t, "cpu_temp", temps[0].SensorKey)
+	})
+
+	t.Run("returns timeout error when collector hangs", func(t *testing.T) {
+		temps, err := agent.getTempsWithTimeout(func(ctx context.Context) ([]sensors.TemperatureStat, error) {
+			time.Sleep(50 * time.Millisecond)
+			return []sensors.TemperatureStat{{SensorKey: "cpu_temp", Temperature: 42}}, nil
+		})
+
+		assert.Nil(t, temps)
+		assert.ErrorIs(t, err, errTemperatureFetchTimeout)
+	})
+}
+
+func TestUpdateTemperaturesSkipsOnTimeout(t *testing.T) {
+	agent := &Agent{
+		systemInfo: system.Info{DashboardTemp: 99},
+		sensorConfig: &SensorConfig{
+			context: context.Background(),
+		},
+	}
+
+	originalTimeout := temperatureFetchTimeout
+	t.Cleanup(func() {
+		temperatureFetchTimeout = originalTimeout
+		getSensorTemps = sensors.TemperaturesWithContext
+	})
+	temperatureFetchTimeout = 10 * time.Millisecond
+	getSensorTemps = func(ctx context.Context) ([]sensors.TemperatureStat, error) {
+		time.Sleep(50 * time.Millisecond)
+		return nil, nil
+	}
+
+	stats := &system.Stats{
+		Temperatures: map[string]float64{"stale": 50},
+	}
+
+	agent.updateTemperatures(stats)
+
+	assert.Equal(t, 0.0, agent.systemInfo.DashboardTemp)
+	assert.Equal(t, map[string]float64{}, stats.Temperatures)
+}