issue_comments

I think this could be solved by one of:

1. Stop generating absolute URLs, e.g. ones that include an origin. Relative URLs with absolute paths are fine, as long as they take base_url into account (as they do now, yay!).
2. Extend base_url to include the expected frontend origin, and then use that information when generating absolute URLs.
3. Document which HTTP headers the reverse proxy should set (e.g. the X-Forwarded-* family of conventional headers) to pass the frontend origin information to Datasette, and then use that information when generating absolute URLs.

Option 1 seems like the easiest to me, if you can get away with never having to generate an absolute URL.

Nod. The problem with the tests is that they're ignoring the origin (hostname, port) of links. In a reverse proxy situation, the frontend request origin is different than the backend request origin. The problem is Datasette generates links with the backend request origin.

@simonw Unfortunately this issue as I reported it is not actually solved in version 0.55.

Every link which is returned by the Datasette.absolute_url method is still wrong, because it uses the request URL as the base. This still includes the suggested facet links and pagination links.

What I wrote originally still stands:

Although many of the URLs in the pages are correct (presumably because they either use absolute paths which include base_url or relative paths), the faceting and pagination links still use fully-qualified URLs pointing at http://localhost:8001.

I looked into this a little in the source code, and it seems to be an issue anywhere request.url or request.path is used, as these contain the values for the request between the frontend (Apache) and backend (Datasette) server. Those properties are primarily used via the path_with_… family of utility functions and the Datasette.absolute_url method.

Would you prefer to re-open this issue or have me create a new one?

@rgieseke Ah, that's super helpful. Thank you for the workaround for now!

Hmm, I haven't tried removing ProxyPassReverse, but it doesn't touch the HTML, which is the issue I'm seeing. You can read the documentation here. ProxyPassReverse is a standard directive when proxying with Apache. I've used it dozens of times with other applications.

Looking a little more at the code, I think the issue here is that the behaviour of base_url makes sense when Datasette is mounted at a path within a larger application, but not when HTTP requests are being proxied to it.

In a mount situation, it is perfectly fine to construct URLs reusing the domain and path from the request. In a proxy situation, it never is, as the domain and path in the request are not the domain and path that the non-proxy client actually needs to use. That is, links which include the Apache → Datasette request origin, localhost:8001, instead of the browser → Apache request origin, example.com, will be broken.

The tests you pointed to also reflect this in two ways:

1. They strip a leading http://localhost, allowing such URLs in the facet links to pass, but inclusion of that in a proxy situation would mean the URL is broken.

2. The test client emits direct ASGI events instead of actual proxied HTTP requests. The headers of these ASGI events don't reflect the way an HTTP proxy works; instead they pass through the original request path which contains base_url. This works because Datasette responds to requests equivalently at either /… or /{base_url}/…, which makes some sense in a mount situation but is unconventional (albeit workable) for a proxied app.

Apps that support being proxied automatically support being mounted, but apps that only support being mounted don't automatically support being proxied.