@Override
    public void shutdown() {
        for (Deque<PooledConnection> connections : connectionsPerEventLoop.values()) {
            for (PooledConnection conn : connections) {
                conn.close();
            }
        }
    }
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