fix(services): HealthChecker.Register triggers immediate poll when running

When Register() is called on an already-started HealthChecker, it now
sends a non-blocking signal on a new chRefresh channel. The run()
goroutine selects on this channel and calls update() immediately, so
the newly registered service is visible in IsHealthy() / IsReady()
without waiting up to 15 s for the next polling tick.

Root cause: the job spawner starts a service then registers it with the
HealthChecker. Before this fix, a dynamically registered service was
absent from health reports for a full polling interval even though
Ready() already returned nil.

Author: Fletch153

pkg/services/health.go

@@ -47,8 +47,9 @@ func CopyHealth(dest, src map[string]error) {
 // HealthChecker is a services.Service which monitors other services and can be probed for system health.
 type HealthChecker struct {
 	StateMachine
-	chStop chan struct{}
-	chDone chan struct{}
+	chStop    chan struct{}
+	chDone    chan struct{}
+	chRefresh chan struct{}
 
 	cfg HealthCheckerConfig
 
@@ -130,12 +131,13 @@ func (cfg HealthCheckerConfig) New() *HealthChecker {
 	cfg.initVerSha()
 	cfg.setNoopHooks()
 	return &HealthChecker{
-		cfg:      cfg,
-		services: make(map[string]HealthReporter, 10),
-		healthy:  make(map[string]error, 10),
-		ready:    make(map[string]error, 10),
-		chStop:   make(chan struct{}),
-		chDone:   make(chan struct{}),
+		cfg:       cfg,
+		services:  make(map[string]HealthReporter, 10),
+		healthy:   make(map[string]error, 10),
+		ready:     make(map[string]error, 10),
+		chStop:    make(chan struct{}),
+		chDone:    make(chan struct{}),
+		chRefresh: make(chan struct{}, 1),
 	}
 }
 
@@ -171,6 +173,8 @@ func (c *HealthChecker) run() {
 		select {
 		case <-ticker.C:
 			c.update(ctx)
+		case <-c.chRefresh:
+			c.update(ctx)
 		case <-c.chStop:
 			return
 		}
@@ -226,6 +230,14 @@ func (c *HealthChecker) Register(service HealthReporter) error {
 		}
 	}
 	c.services[name] = service
+
+	// Signal the run() goroutine to refresh immediately so the newly
+	// registered service is visible without waiting for the next tick.
+	select {
+	case c.chRefresh <- struct{}{}:
+	default: // refresh already pending
+	}
+
 	return nil
 }