private void reportMetricsUnknown(long count) {
        var dimensions = ImmutableMap.of(
                "tenantName", routingApplication.tenant().value(),
                "app", String.format("%s.%s", routingApplication.application().value(), routingApplication.instance().value()),
                "applicationId", routingApplication.toFullString(),
                "clusterid", "routing"
        );
        var context = metric.createContext(dimensions);
        metric.set(UPSTREAM_UNKNOWN_METRIC, count, context);
    }
Report Nginx metrics periodically.

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