public static ConnTimer install(Channel chan, Registry registry, Id metricBase) {
        ConnTimer timer = new ConnTimer(registry, chan, metricBase);
        if (!chan.attr(CONN_TIMER).compareAndSet(null, timer)) {
            throw new IllegalStateException("pre-existing timer already present");
        }
        return timer;
    }
A timer for connection stats.  Not thread-safe.
zuul-core/src/main/java/com/netflix/zuul/monitoring/ConnTimer.java