move tailscaled_health_messages to the health package

cmd/tailscaled/tailscaled.go

@@ -35,7 +35,6 @@
 	"tailscale.com/control/controlclient"
 	"tailscale.com/drive/driveimpl"
 	"tailscale.com/envknob"
-	"tailscale.com/health"
 	"tailscale.com/hostinfo"
 	"tailscale.com/ipn"
 	"tailscale.com/ipn/conffile"
@@ -341,13 +340,6 @@ func run() (err error) {
 
 	sys := new(tsd.System)
 
-	healthTracker := sys.HealthTracker()
-	health.MetricHealthMessage.Set(health.MetricHealthMessageLabel{
-		Severity: "warning",
-	}, expvar.Func(func() any {
-		return healthTracker.OverallErrorCount()
-	}))
-
 	// Parse config, if specified, to fail early if it's invalid.
 	var conf *conffile.Config
 	if args.confFile != "" {

health/health.go

@@ -8,6 +8,7 @@
 import (
 	"context"
 	"errors"
+	"expvar"
 	"fmt"
 	"maps"
 	"net/http"
@@ -898,18 +899,6 @@ func (t *Tracker) OverallError() error {
 	return t.multiErrLocked()
 }
 
-// OverallErrorCount returns the number of errors currently known to the
-// Tracker.
-func (t *Tracker) OverallErrorCount() int64 {
-	if t.nil() {
-		return 0
-	}
-	t.mu.Lock()
-	defer t.mu.Unlock()
-	t.updateBuiltinWarnablesLocked()
-	return int64(len(t.stringsLocked()))
-}
-
 // Strings() returns a string array containing the Text of all Warnings
 // currently known to the Tracker. These strings can be presented to the
 // user, although ideally you would use the Code property on each Warning
@@ -1215,6 +1204,18 @@ func (t *Tracker) ReceiveFuncStats(which ReceiveFunc) *ReceiveFuncStats {
 }
 
 func (t *Tracker) doOnceInit() {
+	metricHealthMessage.Set(metricHealthMessageLabel{
+		Type: "warning",
+	}, expvar.Func(func() any {
+		if t.nil() {
+			return 0
+		}
+		t.mu.Lock()
+		defer t.mu.Unlock()
+		t.updateBuiltinWarnablesLocked()
+		return int64(len(t.stringsLocked()))
+	}))
+
 	for i := range t.MagicSockReceiveFuncs {
 		f := &t.MagicSockReceiveFuncs[i]
 		f.name = (ReceiveFunc(i)).String()
@@ -1246,11 +1247,12 @@ func (t *Tracker) checkReceiveFuncsLocked() {
 	}
 }
 
-type MetricHealthMessageLabel struct {
-	Severity string
+type metricHealthMessageLabel struct {
+	// TODO: break down by warnable.severity as well?
+	Type string
 }
 
-var MetricHealthMessage = usermetric.NewMultiLabelMap[MetricHealthMessageLabel](
+var metricHealthMessage = usermetric.NewMultiLabelMap[metricHealthMessageLabel](
 	"tailscaled_health_messages",
 	"gauge",
 	"Number of health messages broken down by severity.",