public PooledConnection tryGettingFromConnectionPool(EventLoop eventLoop) {
        PooledConnection conn;
        Deque<PooledConnection> connections = getPoolForEventLoop(eventLoop);
        while ((conn = connections.poll()) != null) {

            conn.setInPool(false);

            /* Check that the connection is still open. */
            if (isValidFromPool(conn)) {
                reuseConnCounter.increment();
                connsInUse.incrementAndGet();
                connsInPool.decrementAndGet();
                return conn;
            } else {
                connTakenFromPoolIsNotOpen.increment();
                connsInPool.decrementAndGet();
                conn.close();
            }
        }
        return null;
    }
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