Reject empty resource refresh interval

Author: sjmiller609

cmd/api/config/config.go

@@ -464,14 +464,15 @@ func (c *Config) Validate() error {
 	if c.Metrics.VMLabelBudget <= 0 {
 		return fmt.Errorf("metrics.vm_label_budget must be positive, got %d", c.Metrics.VMLabelBudget)
 	}
-	if c.Metrics.ResourceRefreshInterval != "" {
-		interval, err := time.ParseDuration(c.Metrics.ResourceRefreshInterval)
-		if err != nil {
-			return fmt.Errorf("metrics.resource_refresh_interval must be a valid duration, got %q: %w", c.Metrics.ResourceRefreshInterval, err)
-		}
-		if interval <= 0 {
-			return fmt.Errorf("metrics.resource_refresh_interval must be positive, got %q", c.Metrics.ResourceRefreshInterval)
-		}
+	if strings.TrimSpace(c.Metrics.ResourceRefreshInterval) == "" {
+		return fmt.Errorf("metrics.resource_refresh_interval must not be empty")
+	}
+	interval, err := time.ParseDuration(c.Metrics.ResourceRefreshInterval)
+	if err != nil {
+		return fmt.Errorf("metrics.resource_refresh_interval must be a valid duration, got %q: %w", c.Metrics.ResourceRefreshInterval, err)
+	}
+	if interval <= 0 {
+		return fmt.Errorf("metrics.resource_refresh_interval must be positive, got %q", c.Metrics.ResourceRefreshInterval)
 	}
 	if c.Otel.MetricExportInterval != "" {
 		if _, err := time.ParseDuration(c.Otel.MetricExportInterval); err != nil {

cmd/api/config/config_test.go

@@ -97,9 +97,17 @@ func TestValidateRejectsInvalidVMLabelBudget(t *testing.T) {
 
 func TestValidateRejectsInvalidResourceRefreshInterval(t *testing.T) {
 	cfg := defaultConfig()
-	cfg.Metrics.ResourceRefreshInterval = "not-a-duration"
+	cfg.Metrics.ResourceRefreshInterval = ""
 
 	err := cfg.Validate()
+	if err == nil {
+		t.Fatalf("expected validation error for empty resource refresh interval")
+	}
+
+	cfg = defaultConfig()
+	cfg.Metrics.ResourceRefreshInterval = "not-a-duration"
+
+	err = cfg.Validate()
 	if err == nil {
 		t.Fatalf("expected validation error for invalid resource refresh interval")
 	}