Controlling caching by overriding serve

models.py

from django.template.response import TemplateResponse
from wagtail.core.models import Page, PageViewRestriction

DEFAULT_PAGE_CACHE_TIME = 60 * 5  # 5 minutes


class BasePage(Page):
    """
    This model contains methods we want added to all (or nearly all) of our custom Page types. Right
    now that is our Cache-Control headers. The values for these are a work in progress and for now
    are basically either saying "don't cache locally or on Cloudflare" OR "please cache on
    Cloudflare". I am not setting a browser cache time because it makes it harder for me to test
    rules. And I am using the more general "CDN-Cache-Control" header so I can see that the value is
    getting served. When I use "Cloudflare-CDN-Cache-Control" the header gets stripped so I can't be
    100% sure that it got served and what value it had.
    """
    def is_private(self):
        restricted_pages = PageViewRestriction.objects.values('page_id')
        return self.get_ancestors(inclusive=True).filter(id__in=restricted_pages).exists()

    def cache_control_headers(self, request):
        request.is_preview = getattr(request, 'is_preview', False)
        if request.is_preview or self.is_private():
            return {"Cache-Control": "private, max-age=0, s-maxage=0"}
        else:
            return {"CDN-Cache-Control": f"public, max-age={DEFAULT_PAGE_CACHE_TIME}"}

    def serve(self, request, *args, **kwargs):
        """
        This is essentially a monkey patch of Wagtail's Page.serve() method.
        It's here to set Cache-Control headers depending on page privacy.
        """
        request.is_preview = getattr(request, 'is_preview', False)

        return TemplateResponse(
            request,
            self.get_template(request, *args, **kwargs),
            self.get_context(request, *args, **kwargs),
            headers=self.cache_control_headers(request),
        )

    class Meta:
        abstract = True