externalUrlBase behaves incorrectly with proxies + subscriptions + graphiql

[cmanou]

I'm submitting a ...

• bug report
• feature request
• question

PostGraphile version: 4.4.4 (but applicable to all versions since #1070)

Steps to reproduce:

1. Have a running instance of postgraphile with graphiql enabled (eg: http://localhost:3000/graphql)
2. Have a proxy server in front of the postgraphile server that routes on a path (eg: https://example.com/api/graphql -> http://localhost:3000/graphql)
3. Alternate setting externalUrlBase to /api or undefined

Current behavior:

• If externalUrlBase = /api graphiql will render, and be able to execute mutation + queries. Though any subscriptions requests will fail to complete the upgrade handshake due to the path not matching at https://github.com/DvdGiessen/postgraphile/blob/44c44e2196883b7d659ff796e1eac8c4557e0884/src/postgraphile/http/subscriptions.ts#L157

• If externalUrlBase = '' graphiql will render but will be unable to retrieve the schema or execute any requests. Subscriptions will connect correctly as expected via external clients.
  https://github.com/graphile/postgraphile/blob/master/src/postgraphile/http/createPostGraphileHttpRequestHandler.ts#L401

Expected behavior:
That it works in both cases, this will most likely mean that there will have to be 2 config options as opposed to just externalUrlBase. One option to support the mounting of postgraphile at an express route (ie the reasoning behind the change that was made in #1070 ) and the other which is purely for graphiql config

[benjie]

Yes, you're right - we need two settings here. If we take a slightly more complex example:

https://example.com/api/graphql -> http://localhost:3000/route/graphql

assuming you have something like app.use('/route', postgraphile(...))

To PostGraphile within Express over HTTP we have graphqlRoute = '/graphql' and we can detect originalUrl = '/route/graphql' so we can infer our "internalUrlBase" to be /route but we know nothing about our "actual" location which is /api/graphql. Setting externalUrlBase to /api here should work as expected since we just tell the user externalUrlBase + graphqlRoute is where they can find us.

To PostGraphile websockets we need to match incoming /route/graphql requests directly since we have no express middleware to do the originalUrl dance for us, and we know nothing of the external API. So we need an internalUrlBase = '/route'.

Often externalUrlBase and internalUrlBase are the same, which is how we've got away with having just one setting so far, but apparently no more!

I'd love a PR for this 👍

[danbiagini]

Alright, I'll bite. Just hit this, and seems like a reasonably straight forward place to jump in as 1st time contributor?

[benjie]

I think so! 🙌 Any questions; @ me on #dev-postgraphile in Discord: https://discord.gg/graphile

[benjie]

Hey @danbiagini did you get a chance to look at this?