Improve URL resolver performance

[davidfischer]

Our URL resolver (https://github.com/rtfd/readthedocs.org/blob/4d10f2e/readthedocs/core/resolver.py) which turns a Project and/or Version into a URL to their documentation needs some performance improvements to reduce or eliminate the number of database queries it makes.

This is particularly noticeable on the footer_html API call (https://github.com/rtfd/readthedocs.org/blob/ba71aa1/readthedocs/restapi/templates/restapi/footer.html#L43) which is called on every docs pageview to inject the version selector. In order to get the URL to each version in the version selector, four database queries are needed (to make sure this isn't a subproject or translation and get the domain). So for a project with 10 active versions, we are looking at 40 database queries. Most of this effort is wasted since the data is only needed once for the project.

[aasis21]

Hi @davidfischer, Can I take up this issue.
I realize that the template calls version.get_subdomain_url which calls project.get_docs_url which further calls the resolver mentioned above. we should pass this resolved URL in template directly for reuse. Furthermore, the protocol in resolver function should be changed to https.
Are you suggesting to use Django ORM database optimizations techniques to reduce the count of database queries or some change of layout in the code?

[davidfischer]

That's pretty accurate.

I'm not 100% sure that we should force HTTPS yet (see #3282). While every project hosted by *.readthedocs.io can and should use HTTPS, some docs use their own domain and not all of those support HTTPS (eg. http://docs.python-requests.org)

[davidfischer]

I should mention that I welcome a PR for this. However, I will caution you that this will probably be a bit complex.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.