[Bug]: Pagination NextLink is incorrect in Reverse Proxy scenarios

[vs-dsva]

What happened?

If running DAB behind a reverse proxy that handled SSL termination (https -> http) the next link is broken as it will use http schema instead of https.
I think the issue is in src/Core/Resolvers/SqlResponseHelpers.cs as the link should be constructed either:

1. as a relative link
2. as a schema-less link
3. use the x-forwarded-host and x-forwarded-proto if theyare available

Version

1.4.26

What database are you using?

PostgreSQL

What hosting model are you using?

Custom Docker host

Which API approach are you accessing DAB through?

REST

Relevant log output

Code of Conduct

• I agree to follow this project's Code of Conduct

[JerryNixon]

What happened?

If running DAB behind a reverse proxy that handled SSL termination (https -> http) the next link is broken as it will use http schema instead of https. I think the issue is in src/Core/Resolvers/SqlResponseHelpers.cs as the link should be constructed either:

Not sure if "is broken" correctly captures what is happening. That said, this is a known issue that is on our backlog but isn't likely to come up for a version or so. As a workaround, so you don't have to wait, you can script the server name from the URL and rebuild the NextPage value. I would guess you are already doing exactly this.

var originalNextLink = response.NextLink; // e.g. from DAB response
var newBaseUrl = "https://myapi.example.com";

response.NextLink = RewriteNextLink(originalNextLink, newBaseUrl);

public static string RewriteNextLink(string nextLink, string newBaseUrl)
{
    var uri = new Uri(nextLink);
    var relative = uri.PathAndQuery;

    return $"{newBaseUrl.TrimEnd('/')}{relative}";
}

We'll keep tracking this because you are the second to report this as an issue for your implementation.

[JerryNixon]

That's not the only issue with reverse proxies...

@schuettecarsten
This sort of comment isn't constructive. Please provide details.

[JerryNixon]

Proposed Solution

Reference: https://learn.microsoft.com/en-us/azure/data-api-builder/reference-configuration?tabs=http#pagination-runtime

Option 1: relative

Adding a configuration property for proxy scenarios where the next link is returned relative instead of absolute.

{
  "runtime": {
    "pagination": {
      "next-link-relative": true
    }
  }
}

Default false maintains backward compatibility.

Option 2: replace

Adding a configuration property for proxy scenarios where the next link's authority is hard coded.

{
  "runtime": {
    "pagination": {
      "next-link-authority": "https://myapi.example.com"
    }
  }
}

Update to Include (in either case)

1. Add configuration property
2. Update JSON schema
3. Add JSON schema constraints (no cascading constraints found)
4. Update dab configure --runtime.pagination.next-link-relative true
5. Update dab validate (no cascading constraints found)
6. Update documentation

[schuettecarsten]

That's not the only issue with reverse proxies...

@schuettecarsten
This sort of comment isn't constructive. Please provide details.

Sorry, I will provide additional details soon. We are still investigating if the issue is caused by DAB or by haproxy configuration.

For example, if you use haproxy to host multiple DAB instances on a single URL, remove/rewrite parts of the request path and handle SSL offloading, Swagger UI will not load. Looks like base path setting from DAB is not applied on Swagger UI. But not sure about this.