I must be doing something really stupid without realising

In reply to @kinow:matrix.org
https://github.com/cylc/cylc-uiserver/issues/52

GraphQL schema and versioning...

The UIS provides one GraphQL endpoint for the UI to connect to. The schema for this endpoint is imported from the associated installation of Cylc Flow.

This means that we can represent all workflows with a common schema allowing cross-workflow subscriptions etc. The downside is that in reality each workflow could be running under a different Cylc Version and so have a different schema.

So the UIS becomes the translation layer, when schema changes happen back-compat gets written there to upgrade old schema and fit them into the new model. Because we are using protobuff between the UIS and WS it's not changes in the GraphQL schema but the protobuff schema we need to protect against but it's the same concept.

This approach makes sense, the UI gets a nice stable GraphQL schema to work with. The issue is when we want to handle compatability at the UI rather than the UIS.

At the moment I'm working on mutations in the UI and the whole api-on-the-fly stuff. For this we need the UI to use the same GraphQL schema that the WS is running so that we are working with the correct set of mutations.

So how to give the UI access to this?

1. Don't, always use the most contemporary schema.
   • Unhelpful as it could offer functionality which isn't available or conflicting documentation.
2. Add new GraphQL endpoints at the UIS.
   • Makes cross-workflow mutations a conceptually interesting.
3. Serve the Schema as a JSON object via a new endpoint at the UIS.
   • Mutations get sent to the UIS as JSON, the UIS does the rest.
4. Something else?

For the moment I'm working with the GraphQL schema the UIS provides which is fine for now but towards 1.0.0 we will need to work out what the long-term plan is here.