MongoError: Topology is closed, please connect

Question

I\'m a front-end dev trying to expand my horizons on a new Next project, learning Node, Mongo, and the server side of GraphQL for the first time. Apollo strikes me as the ea

Answer 1

Thanks to GitHub's "Used By" dropdown on the apollo-datasource-mongodb I was able to cheat off a few other repositories, and here's what I ended up with (with changes marked in comments):

const { MongoClient } = require('mongodb');
const assert = require('assert');
const { ApolloServer, gql } = require('apollo-server');
const { MongoDataSource } = require('apollo-datasource-mongodb');


// Isolated these for prominence and reuse
const dbURL = 'mongodb://localhost:27017';
const dbName = 'projectdb';

// Made each function async/await
// Swapped the datasource's findOneById() for the collection itself & standard Mongo functions
class Items extends MongoDataSource {
  async getItem(id) {
    return await this.collection.findOne({id: id});
  }
}

const typeDefs = gql`
  type Item {
    id: Int!
    title: String!
  }
  type Query {
    item(id: Int!): Item
  }
`;

// Made each query async/await
const resolvers = {
  Query: {
    item: async (_, { id }, { dataSources }) => {
      return await dataSources.items.getItem(id);
    },
  }
}

// Move the ApolloServer constructor to its own function that takes the db
const init = (db) = {
  return new ApolloServer({
    typeDefs,
    resolvers,
    dataSources: () => ({
      items: new Items(db.collection('items')),
    }),
  });
}

// Use .connect() instead of new MongoClient
// Pass the new db to the init function defined above once it's been defined
// Call server.listen() from within MongoClient
MongoClient.connect(dbURL, { useNewUrlParser: true, useUnifiedTopology: true }, (err, client) => {
  assert.equal(null, err);
  const db = client.db(dbName);
  console.log(`Mongo database ${ dbName } at ${ dbURL }`);

  const server = init(db);

  server.listen().then(({ url }) => {
    console.log(`Server ready at ${ url }`);
  });
});

With these changes, the Apollo Playground at localhost:4000 works great! Now to solve the 400 error I'm getting in my client app when I query...