Get an estimated operation cost during the `onSubgraphExecute` hook

[slavik-pastushenko]

Hello!

I am wondering if it is possible to access the estimatedCost before actually sending a request to a subgraph?

I see that the calculation is done during this step: https://github.com/graphql-hive/gateway/blob/main/packages/runtime/src/plugins/useDemandControl.ts#L70.

The issue is, I want to know an estimated cost before sending a request, so I can build my logic.

[ardatan]

Could you share more about your scenario?

[slavik-pastushenko]

Sure.

I set up the demandControl option:

demandControl: {
  includeExtensionMetadata: true,
  operationTypeCost: operationType => (operationType === OperationTypeNode.MUTATION ? 10 : 5),
  fieldCost: (_fieldNode, _typeInfo) => 1,
  typeCost: _type => 1,
},

There is an option to specify the maximum cost, and Hive will take care of it. But I want to manually control the maximum cost because it depends on the client who sends a request.

Unfortunately, I am not able to find a way to do that. I was trying to create a custom plugin and intercept a context during the onSubgraphExecute hook, but there is no information about the estimated cost inside.

I researched the way you do it using a plugin; basically, you calculate it and set it as a result in the extensions object.

Is it possible somehow to access the cost before sending a request to a subgraph?

[slavik-pastushenko]

or, maybe you can export the createCalculateCost function?

[slavik-pastushenko]

@ardatan That would be ideal, as I can use your calculation and apply my factors.

[slavik-pastushenko]

btw, I found another bug.
Line 107: https://github.com/graphql-hive/gateway/blob/main/packages/runtime/src/plugins/demand-control/calculateCost.ts#L107

We have OperationDefinition, not OperationTypeDefinition.
And in your docs, it is operationCost as well, but in your codebase, it is operationTypeCost

[ardatan]

So you need maxCost parameter to accept a function that returns the value based on the context, request etc.

About operationTypeCost, it is a typo in the documentation so it should be operationTypeCost not operationCost. operationTypeCost accepts the operation type. Not sure if it s bug. It looks like a mistake in the documentation.
graphql-hive/console#6914

[slavik-pastushenko]

It does not work with the operationTypeCost. It only works with operationCost. I see in your tests that you have 0 cost for queries. Try to add 5 as a cost for queries; that's the easiest way to reproduce.

I don't need maxCost, I want to access the calculated cost before sending a request to a subgraph.