ApolloComplexityPlugin

ApolloComplexityPlugin.ts

import { ApolloServerPlugin, GraphQLServiceContext } from "apollo-server-plugin-base";
import { GraphQLSchema, separateOperations } from "graphql";
import { fieldConfigEstimator, getComplexity, simpleEstimator } from "graphql-query-complexity";

export class ApolloComplexityPlugin implements ApolloServerPlugin {
    private schema: GraphQLSchema;

    constructor(private maxComplexity: number) { }

    public serverWillStart(service: GraphQLServiceContext) {
        this.schema = service.schema;
    }

    public requestDidStart() {
        return {
            didResolveOperation: ({ request, document }) => {
                const complexity = getComplexity({
                    schema: this.schema, query: request.operationName
                        ? separateOperations(document)[request.operationName]
                        : document, variables: request.variables, estimators: [
                            fieldConfigEstimator(),
                            simpleEstimator({ defaultComplexity: 1 }),
                        ]
                });
                if (complexity > this.maxComplexity) {
                    throw new Error(
                        `Sorry, too complicated query (complexity: ${complexity}, max complexity: ${this.maxComplexity})`,
                    );
                }
            }
        };
    }
}