[AS-252] gateway: normalize root operation types in reporting

The federation spec allows your backends to use any name for their root
types (not just the standard Query/Mutation/Subscription) but the composed
schema will always use the standard names.

Both Apollo-maintained implementations of federated trace
reporting (apollo-engine-reporting and federation-jvm) include the backend's
potentially nonstandard name in the federated traces sent to the gateway. Then
the gateway continues to use those names in the traces it sends to AGM.

For example, one of AGM's own implementing services uses QueryRoot, so traces
produced by the gateway in front of it have `QueryRoot` on the traces despite
that type not actually being part of the composed schema.

The effect is that field stats (on the schema explorer) for all root fields are
empty!

Because normalizing root operation names is part of the federation spec, it
makes sense to keep the implementing services simple and fix this just once in
the gateway.

Author: glasser

packages/apollo-federation/src/composition/index.ts

@@ -2,3 +2,4 @@ export * from './compose';
 export * from './composeAndValidate';
 export * from './types';
 export { compositionRules } from './rules';
+export { defaultRootOperationNameLookup } from './normalize';

packages/apollo-federation/src/composition/normalize.ts

@@ -15,18 +15,18 @@ export function normalizeTypeDefs(typeDefs: DocumentNode) {
   );
 }
 
+// Map of OperationTypeNode to its respective default root operation type name
+export const defaultRootOperationNameLookup: {
+  [node in OperationTypeNode]: DefaultRootOperationTypeName;
+} = {
+  query: 'Query',
+  mutation: 'Mutation',
+  subscription: 'Subscription',
+};
+
 export function defaultRootOperationTypes(
   typeDefs: DocumentNode,
 ): DocumentNode {
-  // Map of OperationTypeNode to its respective default root operation type name
-  const defaultRootOperationNameLookup: {
-    [node in OperationTypeNode]: DefaultRootOperationTypeName;
-  } = {
-    query: 'Query',
-    mutation: 'Mutation',
-    subscription: 'Subscription',
-  };
-
   // Array of default root operation names
   const defaultRootOperationNames = Object.values(
     defaultRootOperationNameLookup,

packages/apollo-gateway/src/executeQueryPlan.ts

@@ -12,6 +12,7 @@ import {
   GraphQLFieldResolver,
 } from 'graphql';
 import { Trace, google } from 'apollo-engine-reporting-protobuf';
+import { defaultRootOperationNameLookup } from '@apollo/federation';
 import { GraphQLDataSource } from './datasources/types';
 import {
   FetchNode,
@@ -361,6 +362,19 @@ async function executeFetch<TContext>(
             traceParsingFailed = true;
           }
         }
+        if (traceNode.trace) {
+          // Federation requires the root operations in the composed schema
+          // to have the default names (Query, Mutation, Subscription) even
+          // if the implementing services choose different names, so we override
+          // whatever the implementing service reported here.
+          const rootTypeName =
+            defaultRootOperationNameLookup[
+              context.operationContext.operation.operation
+            ];
+          traceNode.trace.root?.child?.forEach((child) => {
+            child.parentType = rootTypeName;
+          });
+        }
         traceNode.traceParsingFailed = traceParsingFailed;
       }
     }