Varnish full_page cache can't clear

Question

I've recently set my site up with Varnish full_page cache, and I have one specific URL that seems to be "stuck" and I am not able to clear it from the cache.

Last night I went into maintenance mode to do some updates, and this morning one URL is still showing the maintenance page, I guess because it got crawled while the site was down. All the other URLs I've tested are working but this specific one won't load.

This is production so I don't want to do anything crazy, I just want to clear that one page's cache and nothing I've tried works.

I have tried restarting Varnish at the command line but that does not work. Nor does clearing Magento cache on the front end.

I can disable full_page cache at the command line, and then I can see that the page loads properly. Then I restarted Varnish, and turned full_page cache back on, and the page then responded once again with the "Maintenance" page. So Varnish is hard-caching the page response, but how do I purge it?

Magento 2.3.2 and Varnish 6.0.3

Answer 1

I normally use following command:

curl -v -X PURGE -H 'X-Magento-Tags-Pattern: .*' http://your_magento_domain_name

Answer 2

I thought this URL was caching the maintenance page, but that wasn't the case. This specific page was actually crashing when varnish was enabled because of this Magento issue with too-long cache headers.

My fix is described in my response to this issue: Magento 2.3.1 - Issue with catalog search when using php7.2-fpm