@Override
    protected BasicPoolEntry createEntry(RouteSpecificPool rospl,
            ClientConnectionOperator op) {
        createEntryCounter.increment();
        Stopwatch stopWatch = creationTimer.start();
        try {
            return super.createEntry(rospl, op);
        } finally {
            stopWatch.stop();
        }
    }
A connection pool that provides Servo counters to monitor the efficiency. 
Three counters are provided: counter for getting free entries (or reusing entries),
counter for creating new entries, and counter for every connection request.

@author awang
ribbon-httpclient/src/main/java/com/netflix/http4/NamedConnectionPool.java