Subscription error in handler with expressAppFromMiddleware

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1

Hello friends.

I try to realize a graphql subscription in lambda with createHandler function but it doesn’t work. I use serverless to deploy and serverless-offline to develop. And I use neo4j/graphql library to autogenerate the graphql resolvers.

The handler fonction is created by this code :

import { createServer } from "http";
import express from "express";
import { ApolloServer, gql } from "apollo-server-lambda";
import { WebSocketServer } from "ws"; 
import { useServer } from "graphql-ws/lib/use/ws"; 
import DatabaseManager from "../../services/database/DatabaseManager";
import { Neo4jGraphQL, Neo4jGraphQLSubscriptionsSingleInstancePlugin } from "@neo4j/graphql";
import { ApolloServerPluginDrainHttpServer } from "apollo-server-core";

const typeDefs = gql`
  type Movie {
    title: String!
    description: String!
  }
`;

const driver = DatabaseManager.driver;

const neoSchema = new Neo4jGraphQL({
  typeDefs,
  driver,
  plugins: {
    subscriptions: new Neo4jGraphQLSubscriptionsSingleInstancePlugin(),
  },
});

const app = express();
const httpServer = createServer(app);

const wsServer = new WebSocketServer({
  server: httpServer,
  path: "/graphql",
});

const initServer = () => {
  return neoSchema.getSchema().then(async (schema) => {
    const serverCleanup = useServer({ schema }, wsServer);

    const server = new ApolloServer({
      schema,
      context: ({ event }) => ({ req: { headers: event.headers } }),
      plugins: [
        ApolloServerPluginDrainHttpServer({
          httpServer,
        }),
        {
          async serverWillStart() {
            return {
              async drainServer() {
                await serverCleanup.dispose();
              },
            };
          },
        },
      ],
    });

    // If I try :
    //await server.start()
    //I have this error => //Error: When using an ApolloServer subclass from a serverless framework package, you don't need to call start(); just call createHandler().

    // If I try :
    //server.applyMiddleware({app})
    // I have this error => //Error: You must `await server.start()` before calling `server.applyMiddleware()`
    // Then i try to use expressAppFromMiddleware() function to passed app server as middleware.

    const handlerMiddleware = server.createHandler({
      expressGetMiddlewareOptions: {
        cors: {
          origin: "*",
          credentials: true,
        },
      },
      expressAppFromMiddleware(middleware) {
        app.use(middleware);
        return app;
      },
    });

    return handlerMiddleware;
  });
};

export const handler = async (event: any, context: any, callback: any) => {
  const serverHandler = await initServer();

  return serverHandler({ ...event }, context, callback);
};

When i use Studio, I can see the root subscription
Capture d’écran 2023-02-16 à 12.37.56

I tested to create Movies with Postman (POST http ://localhost:4242/channel-subscription)
with graphQL body :

mutation CreateMovies($input: [MovieCreateInput!]!) {
  createMovies(input: $input) {
    movies {
      description
      title
    }
  }
}

and with variables :

{
  "input": [
    {
      "title": "new film",
      "description": "I am description"
    }
  ]
}

The result of createdMovie is : Status 200 OK
And the response is :

{
    "data": {
        "createMovies": {
            "movies": [
                {
                    "description": "I am description",
                    "title": "new film"
                }
            ]
        }
    }
}

Queries also works.

But when I try to realize Subscription with Postman (POST http ://localhost:4242/channel-subscription)
with graphQL body :

subscription MovieCreated($where: MovieSubscriptionWhere) {
  movieCreated(where: $where) {
    event
    timestamp
    createdMovie {
      title
      description
    }
  }
}

and with variables :

{
  "where": {
    "title": "title of new film for subscription test"
  }
}

the result of subscription return:

{
“errors”: [
{
“message”: “Payload is undefined. Can’t call subscriptions resolver directly.”,
“rentals”: [
{
“line”: 2,
column: 3
}
],
“path”: [
“movieCreated”
],
“extensions”: {
“code”: “INTERNAL_SERVER_ERROR”,
“exception”: {
“stacktrace”: [
“Error: Payload is undefined. Can’t call subscriptions resolver directly.”,
" at subscriptionResolve (/Users/Aymeric/my-projects/node_modules/@neo4j/graphql/dist/schema/resolvers/subscriptions/subscribe.js:30:15)“,
" at /Users/Aymeric/my-projects/node_modules/@neo4j/graphql/dist/schema/resolvers/wrapper.js:114:12”,
" at field.resolve (/Users/Aymeric/my-projects/node_modules/apollo-server-core/dist/utils/schemaInstrumentation.js:56:26)“,
" at executeField (/Users/Aymeric/my-projects/node_modules/graphql/execution/execute.js:481:20)”,
" at executeFields (/Users/Aymeric/my-projects/node_modules/graphql/execution/execute.js:413:20)“,
" at executeOperation (/Users/Aymeric/my-projects/node_modules/graphql/execution/execute.js:358:14)”,
" at execute (/Users/Aymeric/my-projects/node_modules/graphql/execution/execute.js:136:20)“,
" at execute (/Users/Aymeric/my-projects/node_modules/apollo-server-core/dist/requestPipeline.js:205:48)”,
" at processGraphQLRequest (/Users/Aymeric/my-projects/node_modules/apollo-server-core/dist/requestPipeline.js:148:34)“,
" at processTicksAndRejections (internal/process/task_queues.js:95:5)”,
" at async processHTTPRequest (/Users/Aymeric/my-projects/node_modules/apollo-server-core/dist/runHttpQuery.js:221:30)"
]
}
}
}
],
“data”: null

I think I have a problem with expressAppFromMiddleware , but I don’t understand where is my error

I specify the code in my serverless.yml who create the function is :

functions:
    channel-subscription:
        handler: ./src/functions/channel-subscription.handler
        description: test subscription with appolo server
        events:
          - http:
              path: /channel-subscription
              method: post
              cors: true
          - http:
              path: /graphql
              method: post
              cors: true