SlidingSync does not work when hosted on path other than / (root)

[dreske]

When sliding-sync is hostet on the same domain, but in a sub path, the url resolution will fail.

Example:
base domain: matrix.example.com
sliding-sync: matrix.example.com/sliding-sync

the URL constructur new URL("/client/server.json", proxyUrl) will create the url matrix.example.com/client/server.json and not as required matrix.example.com/sliding-sync/client/server.json.

Removing the leading slash from the will solve the issue as per the documentation https://developer.mozilla.org/en-US/docs/Web/API/URL/URL

[t3chguy]

The spec specifies the path as an absolute, so the MSC would need clarifying to allow this

[dreske]

This is our https://example.com/.well-known/matrix/client

{
    "org.matrix.msc3575.proxy": {
        "url": "https://matrix.exampe.com/sliding-sync"
    }
}

But element is trying to load https://matrix.exampe.com/client/server.json which fails because of the constructur behaviour.

[t3chguy]

@dreske https://github.com/matrix-org/matrix-spec-proposals/pull/3575/files/7036c29db2b0ea40dccb0c505d6ef4b6085bf192#diff-1f7276cbbee4eeaaca06b07d2fe58312eab735259f2490e28e04710dde77fdcc

[dreske]

I can't follow you.
We've used the default ansible workbook installation and that creates this configuration. Where is the error?

[t3chguy]

The MSC states that the path is as such

It says nothing about it supporting being at a subpath. The ansible script letting this be configured as such is not in line with the MSC.

[richvdh]

I'm rather confused.

But element is trying to load https://matrix.exampe.com/client/server.json which fails because of the constructur behaviour.

I don't see any reference to an object called server.json in either the MSC (https://github.com/matrix-org/matrix-spec-proposals/blob/kegan/sync-v3/proposals/3575-sync.md) or the CS API spec (https://spec.matrix.org/v1.11/client-server-api/).

What am I missing?

[dreske]

I'm rather confused.

But element is trying to load https://matrix.exampe.com/client/server.json which fails because of the constructur behaviour.

I don't see any reference to an object called server.json in either the MSC (https://github.com/matrix-org/matrix-spec-proposals/blob/kegan/sync-v3/proposals/3575-sync.md) or the CS API spec (https://spec.matrix.org/v1.11/client-server-api/).

What am I missing?

I was not talking about the MSC, but the implementation in element and the react sdk. They are loading the server.json to get the URL of the sync service. So I thought this is the way to do it.

[richvdh]

If this endpoint isn't documented anywhere, I don't think the react-sdk should be supporting it at all.

[t3chguy]

If this endpoint isn't documented anywhere, I don't think the react-sdk should be supporting it at all.

It is a healthcheck endpoint for the sliding sync proxy for whilst the implementation on both sides is unstable, this check was added by @kegsay originally