private void reportHealth(RoutingTable table) {
        Collection<RoutingTable.Target> targets = table.asMap().values();
        Map<String, List<ServerGroup.Server>> status = healthStatus.servers().asMap();
        targets.forEach(service -> {
            List<ServerGroup.Server> serversOfUpstream = status.get(service.id());
            if (serversOfUpstream != null) {
                reportMetrics(service, serversOfUpstream);
            } else {
                reportMetricsUnknown(service);
            }
        });

        Set<String> knownUpstreams = targets.stream().map(RoutingTable.Target::id).collect(Collectors.toSet());
        long unknownUpstreamCount = status.keySet().stream()
                                          .filter(upstreamName -> !knownUpstreams.contains(upstreamName))
                                          .count();
        reportMetricsUnknown(unknownUpstreamCount);
    }
Report Nginx metrics periodically.

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