public void collectRouteStats(String route, int statusCode) {

        // increments 200, 301, 401, 503, etc. status counters
        String preciseStatusString = String.format("status_%d", statusCode);
        NamedCountingMonitor preciseStatus = namedStatusMap.get(preciseStatusString);
        if (preciseStatus == null) {
            preciseStatus = new NamedCountingMonitor(preciseStatusString);
            NamedCountingMonitor found = namedStatusMap.putIfAbsent(preciseStatusString, preciseStatus);
            if (found != null) {
                preciseStatus = found;
            } else {
                MonitorRegistry.getInstance().registerObject(preciseStatus);
            }
        }
        preciseStatus.increment();

        // increments 2xx, 3xx, 4xx, 5xx status counters
        String summaryStatusString = String.format("status_%dxx", statusCode / 100);
        NamedCountingMonitor summaryStatus = namedStatusMap.get(summaryStatusString);
        if (summaryStatus == null) {
            summaryStatus = new NamedCountingMonitor(summaryStatusString);
            NamedCountingMonitor found = namedStatusMap.putIfAbsent(summaryStatusString, summaryStatus);
            if (found != null) {
                summaryStatus = found;
            } else {
                MonitorRegistry.getInstance().registerObject(summaryStatus);
            }
        }
        summaryStatus.increment();

        // increments route and status counter
        if (route == null) {
            route = "ROUTE_NOT_FOUND";
        }
        route = route.replace("/", "_");
        ConcurrentHashMap<Integer, RouteStatusCodeMonitor> statsMap = routeStatusMap.get(route);
        if (statsMap == null) {
            statsMap = new ConcurrentHashMap<Integer, RouteStatusCodeMonitor>();
            routeStatusMap.putIfAbsent(route, statsMap);
        }
        RouteStatusCodeMonitor sd = statsMap.get(statusCode);
        if (sd == null) {
            // don't register only 404 status codes (these are garbage endpoints)
            if (statusCode == 404) {
                if (statsMap.size() == 0) {
                    return;
                }
            }

            sd = new RouteStatusCodeMonitor(route, statusCode);
            RouteStatusCodeMonitor sd1 = statsMap.putIfAbsent(statusCode, sd);
            if (sd1 != null) {
                sd = sd1;
            } else {
                MonitorRegistry.getInstance().registerObject(sd);
            }
        }
        sd.update();
    }
collects and increments counts of status code, route/status code and statuc_code bucket, eg 2xx 3xx 4xx 5xx

@param route
@param statusCode
zuul-core/src/main/java/com/netflix/zuul/stats/StatsManager.java