GraphQL Lacking Stale Content Delivery Time Implementation

[AntonEvers]

As a GraphQL consumer using Fastly I want to receive stale content for a specific amount of time after cache invalidation so that I get fast responses more often and so that I do not have to wait for a slower origin request every time cache is invalidated, also in case of server failure.

AC

• stale-while-revalidate will be sent in GraphQL response header cache-control from Adobe Commerce
• The value of stale-while-revalidate will be equal to the configuration field full_page_cache/fastly/fastly_advanced_configuration/stale_ttl titled Stale Content Delivery Time
• stale-if-error will be sent in GraphQL response header cache-control from Adobe Commerce
• The value of stale-if-error will be equal to the configuration field full_page_cache/fastly/fastly_advanced_configuration/stale_error_ttl titled Stale Content Delivery Time in Case of Backend Error
• This functionality should work the same as \Fastly\Cdn\Model\Layout\LayoutPlugin::afterGenerateElements but then for GraphQL requests.

Approved Schema

• none

Technical direction

Recommendation to build this as a plugin to \Magento\Framework\App\Response\Http::setPublicHeaders, right after \Magento\GraphQlCache\Controller\Plugin\GraphQl::afterRenderResult is called.
See vendor/magento/module-graph-ql-cache/etc/graphql/di.xml as example:

<type name="Magento\Framework\App\FrontControllerInterface">
    <plugin name="graphql-dispatch-plugin" type="Magento\GraphQlCache\Controller\Plugin\GraphQl"/>
    <plugin name="front-controller-builtin-cache" type="Magento\PageCache\Model\App\FrontController\BuiltinPlugin"/>
    <plugin name="front-controller-varnish-cache" type="Magento\PageCache\Model\App\FrontController\VarnishPlugin"/>
</type>

Note that this plugin only applies to the GraphQL area.

[vvuksan]

Released in 1.2.186.

[AntonEvers]

@vvuksan please see my comments on the commit, this PR is only half the solution to the mentioned problem, as stale-if-error is still missing.

[dpotkoc]

@AntonEvers stale-if-error will be added.

[vvuksan]

This has been released in 1.2.187.