code: protected void genCounter(final String agent) {
          idsCounter.inc();
          if (!agentCounters.containsKey(agent)) {
              agentCounters.put(agent, registry.counter(MetricRegistry.name(
                      IdWorker.class, "ids_generated_" + agent)));
          }
          agentCounters.get(agent).inc();
      }
docs: Update the counters for a given user agent
  
  @param agent
  User-Agent