protected void updateServerStatsOnConnectCompletion(ChannelFuture cf) {
        if (cf.isSuccess()) {
            server.incrementOpenConnectionsCount();
        } else {
            server.incrementSuccessiveConnectionFailureCount();
            server.addToFailureCount();
            server.decrementActiveRequestsCount();
        }
    }
function to run when a connection is acquired before returning it to caller.
zuul-core/src/main/java/com/netflix/zuul/netty/connectionpool/PerServerConnectionPool.java