void addServerPort(ServerPort serverPort) {
        final ServerPortMetric serverPortMetric = serverPort.serverPortMetric();
        assert serverPortMetric != null;
        if (serverPortMetrics.add(serverPortMetric)) {
            serverPortMetric.bindTo(meterRegistry, serverPort);
        }
    }
A class that holds metrics related server.
core/src/main/java/com/linecorp/armeria/server/ServerMetrics.java