public static ConnCounter install(Channel chan, Registry registry, Id metricBase) {
        ConnCounter counter = new ConnCounter(registry, chan, metricBase);
        if (!chan.attr(CONN_COUNTER).compareAndSet(null, counter)) {
            throw new IllegalStateException("pre-existing counter already present");
        }
        return counter;
    }
An array of locks to guard the gauges.   This is the same as Guava's Striped, but avoids the dep.
<p>
This can be removed after https://github.com/Netflix/spectator/issues/862 is fixed.
zuul-core/src/main/java/com/netflix/zuul/monitoring/ConnCounter.java