Apache SetEnfIf and fullpage cache: Start page shows the same store view for all URLs, once cached

Question

We have a setup with a public facing NGINX reverse proxy that sets the head X-Magento-Store and the shop instance on an apache Vhost

in apache I added

    SetEnv MAGE_RUN_TYPE "store"

    SetEnvIfNoCase X-Magento-Store ^english$ MAGE_RUN_CODE=english
    SetEnvIfNoCase X-Magento-Store ^italian$  MAGE_RUN_CODE=italian

And every thing works fine as long as full_page cache is off.

If full_page cache is on, and I open the Italian URL www.example.com/it-it/shop first, the Italian start page is also shown when opening www.example.com/en_gb/shop and vice versa.

So it seems to me that the store code is missing in the full_page cache key some how, but why?

Steps to reproduce, without proxy setup:

1) In pub/.htaccess set

SetEnv MAGE_RUN_TYPE store SetEnv MAGE_RUN_CODE italy

2) Now open Frontend

3) Now set

SetEnv MAGE_RUN_TYPE store SetEnv MAGE_RUN_CODE english

4) Now Open frontend, same URL

-> Italian version is displayed

Debugging

Setting break point in \Magento\Framework\App\PageCache\Kernel::load

Answer 1

The code in \Magento\Framework\App\PageCache\Identifier::getValue get's the value for the cache key. In our case, the UriString is always the same, so the same data is returned

public function getValue()
{
    $data = [
        $this->request->isSecure(),
        $this->request->getUriString(),
        $this->request->get(\Magento\Framework\App\Response\Http::COOKIE_VARY_STRING)
            ?: $this->context->getVaryString()
    ];
    return sha1($this->serializer->serialize($data));
}

A temporary workaround would be to insert the MAGE_RUN_CODE to the function, but I will work on a better way

public function getValue()
{
    $data = [
        $this->request->isSecure(),
        $this->request->getUriString(),
        $this->request->getServerValue('MAGE_RUN_CODE'),
        $this->request->get(\Magento\Framework\App\Response\Http::COOKIE_VARY_STRING)
            ?: $this->context->getVaryString()
    ];
    return sha1($this->serializer->serialize($data));
}

It is submitted as a pending pull request:

https://github.com/magento/magento2/pull/18624

https://github.com/magento/magento2/pull/18624/commits/d12da9fa10a22443d886ecdcd6a995a36374df2f.patch