feat: healthcheck requires minimum ASN count

main.go

@@ -24,6 +24,8 @@ type server struct {
 	nrenASNs   map[uint]struct{}
 	ready      atomic.Bool
 	versionTag string
+	minASN     int
+	asnCount   int
 }
 
 func loadASNSet(path string) (map[uint]struct{}, error) {
@@ -119,6 +121,7 @@ func main() {
 	asnListPath := getenv("ASN_LIST_PATH", "/data/nren_asns.txt")
 	addr := getenv("ADDR", ":8080")
 	version := getenv("VERSION_TAG", "asn-header-service")
+	minASN := getenvInt("MIN_ASN_COUNT", 10)
 
 	db, err := maxminddb.Open(mmdbPath)
 	if err != nil {
@@ -130,13 +133,26 @@ func main() {
 	if err != nil {
 		log.Fatalf("failed to load asn list: %v", err)
 	}
+	asnCount := len(set)
 
-	s := &server{db: db, nrenASNs: set, versionTag: version}
+	s := &server{
+		db:         db,
+		nrenASNs:   set,
+		versionTag: version,
+		minASN:     minASN,
+		asnCount:   asnCount,
+	}
 	s.ready.Store(true)
 
 	mux := http.NewServeMux()
 	mux.HandleFunc("/auth", s.authHandler)
-	mux.HandleFunc("/healthz", func(w http.ResponseWriter, _ *http.Request) { w.WriteHeader(http.StatusOK) })
+	mux.HandleFunc("/healthz", func(w http.ResponseWriter, _ *http.Request) {
+		if s.asnCount < s.minASN {
+			w.WriteHeader(http.StatusServiceUnavailable)
+			return
+		}
+		w.WriteHeader(http.StatusOK)
+	})
 
 	srv := &http.Server{
 		Addr:              addr,
@@ -144,7 +160,7 @@ func main() {
 		ReadHeaderTimeout: 2 * time.Second,
 	}
 
-	log.Printf("listening on %s (asn_count=%d)", addr, len(set))
+	log.Printf("listening on %s (asn_count=%d, min_asn=%d)", addr, asnCount, minASN)
 	log.Fatal(srv.ListenAndServe())
 }
 
@@ -156,3 +172,14 @@ func getenv(k, def string) string {
 	return v
 }
 
+func getenvInt(k string, def int) int {
+	v := strings.TrimSpace(os.Getenv(k))
+	if v == "" {
+		return def
+	}
+	parsed, err := strconv.Atoi(v)
+	if err != nil {
+		return def
+	}
+	return parsed
+}