Category X-Magento-Tags too long causing Varnish to 503

[djfordz]

I have a customer site that Varnish is 503'ing on Category pages that have a too long X-Magento-Tags similar to this issue here: #6401.

Preconditions

1. Magento 2.1.3
2. CentOS 6
3. Mysql Ver 14.14 Distrib 5.6.32-78.1
4. PHP 7.0.16

Steps to reproduce

1. Enable Varnish for page cache
2. Add over 5000 categories greater than 4 levels deep each level with hundreds more categories
3. try to goto category page

Expected result

1. Category Page displays

Actual result

1. [Screenshot, logs]
   503 Varnish Cache Error
   

[ljrweb]

I ran into this problem and I think Magento updated documentation to explain how to extend the parameter value in the varnish config.

http://devdocs.magento.com/guides/v2.0/config-guide/varnish/tshoot-varnish-503.html

[dcabrejas]

I have encountered this issue on a Magento site running on 2.1.5. Category pages containing a large number of products return aX-Magento-Tag header which is bigger than the size allowed by the HTTP specification.

We have implemented this workaround for now http://devdocs.magento.com/guides/v2.0/config-guide/varnish/tshoot-varnish-503.html

But this is not a solution, just a workaround because the http header size is still larger than the limit set by the HTTp specification.

[magento-engcom-team]

@djfordz, thank you for your report.
This seems to be correct Magento behavior. Please refer to the Community Forums or the Magento Stack Exchange site for advice or general discussion about this.
Otherwise you may submit Pull Request with the suggested changes.