Cost directives from subgraphs not seem to be respected by Demand Control in Gateway

[arekgwizdziel]

Hey,

Firstly, thanks for a beautiful work you're doing here!

I have pretty general question about Federation + Gateway + (I think Hive itself).

I want to use Gateway with Demand Control to limit the query cost.

For subgraphs I use HotChocolate framework, I push my subgraph schemas to Hive Registry and use Gateway as a router.

The issue I'm having right now is that Demand Control seems to ignore the subgraph's @cost and @listsize directives. Also I don't see the changes in Hive Registry regarding them. They're visible in Service tab in Hive but they're omitted in Schema tab.

After brief investigation, I have a suspicion that it might be related to Federation version and directives that are available in them.

My subgraph schema looks like this:

`schema @link(url: "https://specs.apollo.dev/federation/v2.6", import: ["@Shareable", "@external", "@tag", "@key", "@requires", "FieldSet"]) {
query: Query
}
directive @cost(
weight: String!
) on SCALAR | OBJECT | FIELD_DEFINITION | ARGUMENT_DEFINITION | ENUM | INPUT_FIELD_DEFINITION

directive @listsize(
assumedSize: Int
slicingArguments: [String!]
slicingArgumentDefaultValue: Int
sizedFields: [String!]
requireOneSlicingArgument: Boolean! = true
) on FIELD_DEFINITION`

Can someone confirm the fact that I need to raise the Federation version link to 2.9 and import directives from Federation spec instead of defining them in order for Demand Control to work?

[ardatan]

Can someone confirm the fact that I need to raise the Federation version link to 2.9 and import directives from Federation spec instead of defining them in order for Demand Control to work?

You need to import directives from Federation spec, yes.

Gateway does not ignore them, in order to have custom directives in your supergraph, you have to import them using @link.
Gateway cannot know you have those directives in your subgraph if it doesn't exist in the supergraph. You can check your supergraph if those directives exist, but as I see the xample you shared, it doesn't look like it will have in your supergraph.

[arekgwizdziel]

Thank you for quick answer, so I'm still a bit confused as after I added these import items by hand (as subgraph library still doesn't support 2.9 spec), I get

Invalid version v2.9 for the federation feature in @link directive on schema

from Hive when I'm running schema composition checks.

I've downloaded Apollo demo repo and I was getting the same error when using older version of @apollo/subgraph NPM package, after I upgraded it to latest- it started working. It got me thinking: does Hive support this spec? I'm using latest hive-cli.

I think the answer is no, looking at the federation-composition package. I can't see any sign of 2.9 spec there.

That would mean that using Hive and Federation, there is no possibility to use Demand Control, right?

[ardatan]

Unfortunately Hive Console doesn't support v2.9 yet. It is on Hive Console's roadmap.
You can treat @cost as an additional directive until it is supported by default if you use Hive Console.

https://www.apollographql.com/docs/graphos/reference/federation/directives#composedirective

[arekgwizdziel]

Oh, wasn't aware of that! Will try it, thank you very much!