@Monitor(name="connectionCount", type=DataSourceType.GAUGE)
    public int getConnectionCount() {
        return this.getConnectionsInPool();
    }
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