一、cookie

protected $_cookieManager;

private $_cookieMetadataFactory;

private $_sessionManager;

public function __construct(

\Magento\Framework\Stdlib\Cookie\PhpCookieManager $cookieManager,

\Magento\Framework\Stdlib\Cookie\CookieMetadataFactory $cookieMetadataFactory,
    \Magento\Framework\Session\SessionManagerInterface $sessionManager

) {

$this->_cookieManager = $cookieManager;
        $this->_cookieMetadataFactory = $cookieMetadataFactory;
        $this->_sessionManager = $sessionManager;
}

public function execute(\Magento\Framework\Event\Observer $observer){

//第一次访问，还没有cookie记录
        if ($this->_cookieManager->getCookie('olight_geoip') === null) {
            $metadata = $this->_cookieMetadataFactory
                                                ->createPublicCookieMetadata()
                                                ->setDuration(86400)
                                                ->setPath($this->_sessionManager->getCookiePath())
                                                ->setDomain($this->_sessionManager->getCookieDomain());
            $this->_cookieManager->setPublicCookie('olight_geoip',1,$metadata);

}

//删除cookie

$this->_cookieManager->deleteCookie('olight_geoip');

}

二、session

session 列表

/magento/module-catalog/Model/Session.php
/magento/module-newsletter/Model/Session.php
/magento/module-persistent/Model/Session.php
/magento/framework/Message/Session.php
/magento/module-customer/Model/Session.php
/magento/module-backend/Model/Session.php
/magento/module-checkout/Model/Session.php

下面，以/magento/module-checkout/Model/Session.php为例

<?php

$checkoutSession = $this->_objectManager->create('Magento\Checkout\Model\Session');

//set session
$sessionName = 'setFatherDayCustomer'.$customerId;
$checkoutSession->$sessionName(true);
                
//get session
$sessionName = 'getFatherDayCustomer'.$customerId;
$fatherDayCustomer = $checkoutSession->$sessionName();

//unset session
$sessionName = 'unsFatherDayCustomer'.$customerId;
$checkoutSession->$sessionName();

?>