public static ConnCounter from(Channel chan) {
        Objects.requireNonNull(chan);
        ConnCounter counter = chan.attr(CONN_COUNTER).get();
        if (counter != null) {
            return counter;
        }
        if (chan.parent() != null && (counter = chan.parent().attr(CONN_COUNTER).get()) != null) {
            return counter;
        }
        throw new IllegalStateException("no counter on channel");
    }
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