I spent several hours finding the best way to implementgraphql-query-complexity with Apollo server v3 (server and serverless)
and I just wanted to post the answer in case anyone else needs it.

The trouble I ran into is that apollo server doesn't give its validationRules access to the request object so calculating query complexity based on request parameters is not possible. In apollo validationRules arenot guaranteed to run on every request.

The solution is to use the plugin api's didResolveOperation hook to manually trigger a complexity calculation further along the request pipeline asexplained here.

If you are using express (apollo-server-express or apollo-server-lambda or apollo-server-cloud-functions) you could probably do this as express middleware as well.

Feel free to close this Issue.

EDIT: You will need to modify the code example to work with the latest version ofgraphql-query-complexity (fieldConfigEstimator is deprecated). If you are using Apollo and building your schema usinggql() you may also need to convert your schema into a GraphQLSchema. Graphql includes a utility to do thisimport { buildASTSchema } from 'graphql';.