Apollo data source for MongoDB

npm i apollo-datasource-mongodb

This package uses DataLoader for batching and per-request memoization caching. It also optionally (if you provide a ttl) does shared application-level caching (using either the default Apollo InMemoryLRUCache or the cache you provide to ApolloServer()). It does this only for these two methods:

• findOneById(id, options)
• findManyByIds(ids, options)

Contents:

• Usage
  • Basic
  • Batching
  • Caching
• API
  • findOneById
  • findManyByIds
  • deleteFromCacheById

Usage

Basic

The basic setup is subclassing MongoDataSource, passing your collection or Mongoose model to the constructor, and using the API methods:

data-sources/Users.js

import { MongoDataSource } from 'apollo-datasource-mongodb'

export default class Users extends MongoDataSource {
  getUser(userId) {
    return this.findOneById(userId)
  }
}

and:

import { MongoClient } from 'mongodb'

import Users from './data-sources/Users.js'

const client = new MongoClient('mongodb://localhost:27017/test')
client.connect()

const server = new ApolloServer({
  typeDefs,
  resolvers,
  dataSources: () => ({
    users: new Users(client.db().collection('users'))
    // OR
    // users: new Users(UserModel)
  })
})

Inside the data source, the collection is available at this.collection (e.g. this.collection.update({_id: 'foo, { $set: { name: 'me' }}})). The model (if applicable) is available at this.model (new this.model({ name: 'Alice' })). The request's context is available at this.context. For example, if you put the logged-in user's ID on context as context.currentUserId:

class Users extends MongoDataSource {
  ...

  async getPrivateUserData(userId) {
    const isAuthorized = this.context.currentUserId === userId
    if (isAuthorized) {
      const user = await this.findOneById(userId)
      return user && user.privateData
    }
  }
}

If you want to implement an initialize method, it must call the parent method:

class Users extends MongoDataSource {
  initialize(config) {
    super.initialize(config)
    ...
  }
}

Batching

This is the main feature, and is always enabled. Here's a full example:

class Users extends MongoDataSource {
  getUser(userId) {
    return this.findOneById(userId)
  }
}

class Posts extends MongoDataSource {
  getPosts(postIds) {
    return this.findManyByIds(postIds)
  }
}

const resolvers = {
  Post: {
    author: (post, _, { users }) => users.getUser(post.authorId)
  },
  User: {
    posts: (user, _, { posts }) => posts.getPosts(user.postIds)
  }
}

const server = new ApolloServer({
  typeDefs,
  resolvers,
  dataSources: () => ({
    users: new Users(db.collection('users')),
    posts: new Posts(db.collection('posts'))
  })
})

Caching

To enable shared application-level caching, you do everything from the above section, and you add the ttl option to findOneById():

const MINUTE = 60

class Users extends MongoDataSource {
  getUser(userId) {
    return this.findOneById(userId, { ttl: MINUTE })
  }

  updateUserName(userId, newName) {
    this.deleteFromCacheById(userId)
    return this.collection.updateOne({ 
      _id: userId 
    }, {
      $set: { name: newName }
    })
  }
}

const resolvers = {
  Post: {
    author: (post, _, { users }) => users.getUser(post.authorId)
  },
  Mutation: {
    changeName: (_, { userId, newName }, { users, currentUserId }) => 
      currentUserId === userId && users.updateUserName(userId, newName)
  }
}

Here we also call deleteFromCacheById() to remove the user from the cache when the user's data changes. If we're okay with people receiving out-of-date data for the duration of our ttl—in this case, for as long as a minute—then we don't need to bother adding calls to deleteFromCacheById().

API

findOneById

this.findOneById(id, { ttl })

Resolves to the found document. Uses DataLoader to load id. DataLoader uses collection.find({ _id: { $in: ids } }). Optionally caches the document if ttl is set (in whole seconds).

findManyByIds

this.findManyByIds(ids, { ttl })

Calls findOneById() for each id. Resolves to an array of documents.

deleteFromCacheById

this.deleteFromCacheById(id)

Deletes a document from the cache.