private Id buildId(Id base, String from, String to, Map<String, String> tags) {
        return registry.createId(metricBase.name() + '.' + from + '-' + to)
                .withTags(base.tags())
                .withTags(tags);
    }
A timer for connection stats.  Not thread-safe.
zuul-core/src/main/java/com/netflix/zuul/monitoring/ConnTimer.java