private void reportMetrics(RoutingTable.Target target, List<ServerGroup.Server> servers) {
        long up = countStatus(servers, true);
        long down = countStatus(servers, false);

        var dimensions = metricsDimensionsForService(target);
        var context = metric.createContext(dimensions);
        metric.set(UPSTREAM_UP_METRIC, up, context);
        metric.set(UPSTREAM_DOWN_METRIC, down, context);
        metric.set(UPSTREAM_UNKNOWN_METRIC, 0L, context);
    }
Report Nginx metrics periodically.

@author Morten Tokle
@author Martin Polden
routing-generator/src/main/java/com/yahoo/vespa/hosted/routing/nginx/NginxMetricsReporter.java