fix: correct telemetry identifier and visibility when containerized

Three related fixes for running Monitor inside a container with
/:/host:ro bind-mounted and network_mode: host.

* config: when HF_MONITER_ROOTFS is set, read the default identifier
  from <rootFS>/etc/hostname instead of os.Hostname(). Under
  network_mode: host the UTS namespace is not shared, so os.Hostname()
  returns a random docker-assigned string that changes across
  recreations, causing the backend to treat each restart as a new
  server.

* telemetry: log gopsutil errors from BuildPayload instead of silently
  swallowing them. Previously a missing /host mount would send a
  payload full of zeroed fields with no indication of failure.

* docker-compose: drop the 'ports:' block. It is silently ignored
  under network_mode: host (the bridge server binds directly on the
  host's 127.0.0.1:MONITOR_PORT).

docker-compose.yml

@@ -15,8 +15,8 @@ services:
       - MONITOR_PORT=${MONITOR_PORT:-0}
     volumes:
       - /:/host:ro
-    ports:
-      # Expose MONITOR_PORT on 127.0.0.1 only for plugin communication.
-      # Only active when MONITOR_PORT > 0.
-      - "127.0.0.1:${MONITOR_PORT:-9100}:${MONITOR_PORT:-9100}"
+    # network_mode: host shares the host network namespace, so the bridge
+    # server (if MONITOR_PORT > 0) listens directly on the host's
+    # 127.0.0.1:<MONITOR_PORT>. `ports:` is ignored under network_mode:
+    # host, so it is intentionally omitted.
     network_mode: host

internal/config/config.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"strings"
 )
 
 type Config struct {
@@ -32,9 +33,19 @@ func Load(path string) (Config, error) {
 }
 
 func LoadWithOverrides(path string, overrides Overrides) (Config, error) {
+	// If running inside a container with the host FS bind-mounted, prefer
+	// the host's /etc/hostname for the default identifier. The container's
+	// own os.Hostname() is a docker-assigned random string under
+	// network_mode: host (UTS namespace is not shared).
+	rootFSEarly := getenvAny([]string{"HF_MONITER_ROOTFS", "HF_MONITOR_ROOTFS"}, "")
+	defaultIdentifier := hostHostname(rootFSEarly)
+	if defaultIdentifier == "" {
+		defaultIdentifier = hostnameOr("unknown-host")
+	}
+
 	cfg := Config{
 		BackendURL:        getenvAny([]string{"HF_MONITER_BACKEND_URL", "HF_MONITOR_BACKEND_URL"}, "https://monitor.hangman-lab.top"),
-		Identifier:        getenvAny([]string{"HF_MONITER_IDENTIFIER", "HF_MONITOR_IDENTIFIER"}, hostnameOr("unknown-host")),
+		Identifier:        getenvAny([]string{"HF_MONITER_IDENTIFIER", "HF_MONITOR_IDENTIFIER"}, defaultIdentifier),
 		APIKey:            getenvAny([]string{"HF_MONITER_API_KEY", "HF_MONITOR_API_KEY"}, ""),
 		ReportIntervalSec: getenvIntAny([]string{"HF_MONITER_REPORT_INTERVAL", "HF_MONITOR_REPORT_INTERVAL"}, 30),
 		LogLevel:          getenvAny([]string{"HF_MONITER_LOG_LEVEL", "HF_MONITOR_LOG_LEVEL"}, "info"),
@@ -153,11 +164,25 @@ func getenvIntAny(keys []string, fallback int) int {
 }
 
 func hostnameOr(fallback string) string {
-	name, err := os.Hostname()
-	if err != nil || name == "" {
-		return fallback
+	if name, err := os.Hostname(); err == nil && name != "" {
+		return name
 	}
-	return name
+	return fallback
+}
+
+// hostHostname reads the hostname from <rootFS>/etc/hostname. Used when
+// Monitor runs inside a container and wants the host's hostname rather
+// than the container's UTS namespace hostname (which docker randomizes
+// unless hostname: is set).
+func hostHostname(rootFS string) string {
+	if rootFS == "" {
+		return ""
+	}
+	buf, err := os.ReadFile(filepath.Join(rootFS, "etc", "hostname"))
+	if err != nil {
+		return ""
+	}
+	return strings.TrimSpace(string(buf))
 }
 
 func applyHostFSEnv(rootFS string) {

internal/telemetry/telemetry.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"log"
 	"net/http"
 	"os"
 	"os/exec"
@@ -50,12 +51,15 @@ func BuildPayload(ctx context.Context, cfg config.Config) (Payload, error) {
 	}
 
 	cpuPct, err := cpu.PercentWithContext(ctx, time.Second, false)
-	if err == nil && len(cpuPct) > 0 {
+	if err != nil {
+		log.Printf("telemetry: cpu.Percent failed: %v", err)
+	} else if len(cpuPct) > 0 {
 		payload.CPUPct = round1(cpuPct[0])
 	}
 
-	vm, err := mem.VirtualMemoryWithContext(ctx)
-	if err == nil {
+	if vm, err := mem.VirtualMemoryWithContext(ctx); err != nil {
+		log.Printf("telemetry: mem.VirtualMemory failed: %v", err)
+	} else {
 		payload.MemPct = round1(vm.UsedPercent)
 	}
 
@@ -63,28 +67,33 @@ func BuildPayload(ctx context.Context, cfg config.Config) (Payload, error) {
 	if diskPath == "" {
 		diskPath = "/"
 	}
-	diskUsage, err := disk.UsageWithContext(ctx, diskPath)
-	if err == nil {
+	if diskUsage, err := disk.UsageWithContext(ctx, diskPath); err != nil {
+		log.Printf("telemetry: disk.Usage(%s) failed: %v", diskPath, err)
+	} else {
 		payload.DiskPct = round1(diskUsage.UsedPercent)
 	}
 
-	swapUsage, err := mem.SwapMemoryWithContext(ctx)
-	if err == nil {
+	if swapUsage, err := mem.SwapMemoryWithContext(ctx); err != nil {
+		log.Printf("telemetry: mem.SwapMemory failed: %v", err)
+	} else {
 		payload.SwapPct = round1(swapUsage.UsedPercent)
 	}
 
-	avg, err := gopsload.AvgWithContext(ctx)
-	if err == nil {
+	if avg, err := gopsload.AvgWithContext(ctx); err != nil {
+		log.Printf("telemetry: load.Avg failed: %v", err)
+	} else {
 		payload.LoadAvg = []float64{round2(avg.Load1), round2(avg.Load5), round2(avg.Load15)}
 	}
 
-	hostInfo, err := host.InfoWithContext(ctx)
-	if err == nil {
+	if hostInfo, err := host.InfoWithContext(ctx); err != nil {
+		log.Printf("telemetry: host.Info failed: %v", err)
+	} else {
 		payload.UptimeSeconds = hostInfo.Uptime
 	}
 
-	nginxInstalled, nginxSites, err := detectNginx(cfg.RootFS)
-	if err == nil {
+	if nginxInstalled, nginxSites, err := detectNginx(cfg.RootFS); err != nil {
+		log.Printf("telemetry: detectNginx failed: %v", err)
+	} else {
 		payload.NginxInstalled = nginxInstalled
 		payload.NginxSites = nginxSites
 	}