fixes

cmd/spike-alerts/main.go

@@ -52,6 +52,7 @@ func main() {
 	cfg := features.SpikeConfig{Window: *window, BaselineWindows: *baselineWindows, Multiple: *multiple, MinExcess: *minExcess}
 
 	events := load(*addr, *database, *user, *password, start, end)
+	cfg.DataSince = dataSince(*addr, *database, *user, *password)
 	log.Printf("loaded %d error events", len(events))
 
 	cache := map[string]classification{}
@@ -212,3 +213,23 @@ func envOr(k, f string) string {
 	}
 	return f
 }
+
+// dataSince returns the earliest normalized row, used as the warm-up guard.
+func dataSince(addr, database, user, password string) time.Time {
+	ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
+	defer cancel()
+	conn, err := clickhouse.Open(&clickhouse.Options{Addr: []string{addr}, Auth: clickhouse.Auth{Database: database, Username: user, Password: password}})
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer conn.Close()
+	var t time.Time
+	if err := conn.QueryRow(ctx, fmt.Sprintf(`SELECT min(timestamp) FROM %s.normalized_events`, database)).Scan(&t); err != nil {
+		log.Printf("warm-up guard disabled: %v", err)
+		return time.Time{}
+	}
+	if t.Year() < 2000 { // empty table
+		return time.Time{}
+	}
+	return t
+}