How to pass through headers?

[tichopad]

Hey everyone!

I'm trying to stitch together (ha!) a proxy gateway for a GraphQL microservice using schema stitching.

The way I'm set up is - there's a Yoga server (with Schema Stitching) on AWS Lambda + API Gateway. It acts as a proxy for 2 sub-schemas:

1. Remote one (using buildHTTPExecutor)
2. Local one (defined using Pothos)

The setup works perfectly when there's no authorization. But the remote sub-schema requires a valid JWT token in an Authorization header. The initial request contains the header, but I cannot figure out how to pass it to the remote executor.

The closest thread I found is #5241 but it doesn't really describe how they were able to get the header to remote executor's context.

Could someone point me in the right direction, please? I'm at my wit's end.

This is what I'm working with right now:

import { buildHTTPExecutor } from "@graphql-tools/executor-http";
import { stitchSchemas } from "@graphql-tools/stitch";
import { schemaFromExecutor } from "@graphql-tools/wrap";
import SchemaBuilder from "@pothos/core";
import { createYoga } from "graphql-yoga";
import { GraphQLSchema } from "graphql";

// Local subschema

const builder = new SchemaBuilder({});

builder.queryType({
  fields: (t) => ({
    hello: t.string({
      nullable: false,
      resolve: () => "world",
    }),
  }),
});

const localSchema = builder.toSchema();

// The entire stitched schema

let stitchedSchema: GraphQLSchema;
const createStitchedSchema = async () => {
  // Remote subschema
  const appSyncRemoteExecutor = buildHTTPExecutor({
    endpoint: "https://remoteschema.example/graphql",
    headers: (executorRequest) => {
      // How can I get the header into executorRequest.context ?
    },
  });

  const appSyncRemoteSubschema = {
    schema: await schemaFromExecutor(appSyncRemoteExecutor),
    executor: appSyncRemoteExecutor,
  };

  return stitchSchemas({
    subschemas: [appSyncRemoteSubschema, localSchema],
  });
};

export const handler = async (event, context) => {
  if (stitchedSchema === undefined) {
    stitchedSchema = await createStitchedSchema();
  }

  const yoga = createYoga({
    schema: stitchedSchema,
    // This doesn't really help
    context: { headers: event.headers },
  });

  const queryParamEntries = Object.entries(event.queryStringParameters);
  const safeQueryParamEntries = queryParamEntries.map(([key, value]) => [
    key,
    value ?? "",
  ]);
  const queryUrlSearchParams = new URLSearchParams(safeQueryParamEntries);
  const fetchPath = event.path + "?" + queryUrlSearchParams.toString();

  const body = event.body
    ? Buffer.from(event.body, event.isBase64Encoded ? "base64" : "utf8")
    : undefined;

  const fetchContext = {
    method: event.httpMethod,
    headers: event.headers,
    body,
  };

  const response = await yoga.fetch(fetchPath, fetchContext, {
    event,
    context,
  });

  return {
    statusCode: response.status,
    body: await response.text(),
    isBase64Encoded: false,
  };
};

[ardatan]

You can find request with headers in it inside executorRequest.contextValue.

[tichopad]

Thanks for the ultrafast reply!

There's no contextValue property on executorRequest. There's document (I presume the operation being executed) and context - which is undefined.
Feels like I have to pass the context in somehow, but I can't figure it out.

[ardatan]

Sorry my mistake. It should be "context". In the introspection request to fetch the schema from the service, "context" is undefined because it is not done by the user request but the gateway to fetch the schema via "schemaFromExecutor". If you want to have context there as well, you can pass a context to the function, too.

[tichopad]

You're right! Thanks!

I noticed that after swapping schemaFromExecutor for a static JSON schema definition the context is properly set. Appreciate the help! ❤️