private void announceAllAvailableConnection() {
        logger.debug("Announce to all connection available on {}", host);
        logConnectionPoolStatus();
        
        waitLock.lock();
        try {
            hasAvailableConnection.signalAll();
        } finally {
            waitLock.unlock();
        }
    }
Get an available connection from the pool. Also triggers consideration of a new connection if the least-used
connection has hit the usage maximum or no valid connection could be retrieved from the pool.

@return an available connection from the pool. Returns null if no valid connection could be retrieved from the
pool.
gremlin-driver/src/main/java/org/apache/tinkerpop/gremlin/driver/ConnectionPool.java