Apollo DataSource for CosmosDB

This is a CosmosDB DataSource for the Apollo GraphQL Server. It was adapted from the MongoDB Data Source project.

Usage

Use by creating a new class, inheriting from CosmosDataSource passing in the CosmosDb container instance (created from the CosmosDB Javascript API). Use a separate DataSource for each data type.

Example:

data-sources/Users.ts

export interface UserDoc {
  id: string; // a string id value is required for entities using this library
  name: string;
}

export class UserDataSource extends CosmosDataSource<UserDoc> {}
export class PostDataSource extends CosmosDataSource<PostDoc> {}

server.ts

import { CosmosClient } from "@azure/cosmos";
import { CosmosDataSource } from "apollo-datasource-cosmosdb";

const cosmosClient = new CosmosClient({
  endpoint: "https://my-cosmos-db.documents.azure.com:443/",
  key: "--------key-goes-here---==",
});
const cosmosContainer = cosmosClient.database("MyDatabase").container("Items");

import UserDataSource from "./data-sources/Users.js";
import PostDataSource from "./data-sources/Users.js";

const server = new ApolloServer({
  typeDefs,
  resolvers,
  dataSources: () => ({
    users: new UserDataSource(cosmosContainer),
    posts: new PostDataSource(cosmosContainer),
  }),
});

Context

It is often useful to define a context. See Apollo docs on context To make this strongly typed, there is a second type paramater on the CosmosDbDataSource:

interface MyQueryContext {
  currentUserId: string
}

/////

const userDataSource extends CosmosDataSource<UserDoc, MyQueryContext> {}

Custom Queries

CosmosDataSource exposes a findManyByQuery method that accepts a ComosDB SQL query either as a string or a SqlQuerySpec object containing the query and a parameter collection. This can be used directly in the resolvers, but probably better to create wrappers that hide the query details.

Creating a derived class with custom query methods, you can hide all of your query logic in the DataSource class:

export class UserDataSource extends CosmosDataSource<UserDoc, ApolloContext> {
  findManyByGroupID = async (group_id, args: FindArgs = {}) => {
    log.debug(`UserDataSource: getGroupUsers ${group_id}`);
    const query = `SELECT * FROM c where c.type = "User" and exists(select * from g in c.groups where g = @group_id) `;
    const results = await this.findManyByQuery(
      {
        query,
        parameters: [{ name: "@group_id", value: group_id }],
      },
      args
    );
    log.debug(`Result count ${results.resources.length}`);
    return results.resources;
  };
  findOneByUserName = async (userName: string, args: FindArgs = {}) => {
    const results = await this.findManyByQuery(
      {
        query: `SELECT * FROM c WHERE c.userName = @userName AND c.type = 'User'`,
        parameters: [{ name: "@userName", value: userName }],
      },
      args
    );
    if (results.resources && results.resources.length)
      return results.resources[0];
    return undefined;
  };
}

Write Operations

This DataSource has some built in mutation methods to create, update and delete items. They can be used directly in resolvers or wrapped with custom methods.

await context.dataSources.users.createOne(userDoc);

await context.dataSources.users.updateOne(userDoc);

await context.dataSources.users.updateOnePartial(user_id, { name: "Bob" });

await context.dataSources.users.deleteOne(userId);

The data loader (and cache, if used) are updated after mutation operations.

Batching

Batching is provided on all queries using the DataLoader library.

Caching

Caching is available on an opt-in basis by passing a ttl option on queries.

Typescript

This library is written in Typescript and exports full type definitions, but usable in pure Javascript as well. This works really well with GraphQL Codegen's typed resolvers.

API

const thisUser = await users.findOneById(id: string, {ttl})  // => Promise<T | undefined>

const userPair = await users.findManyByIds([id1, id2], {ttl}) // => Promise<(T | undefined)[]>

await users.deleteFromCacheById(id}) // => Promise<void>

// query method; note that this returns the CosmosDB FeedResponse object because sometimes this extra information is useful
const userListResponse = await users.findManyByQuery('SELECT * from c where c.type="User"', {ttl, requestOptions}) // => Promise<FeedResponse<T>>
console.log(userListResponse.resources) // user array from query

// create method returns the CosmosDB ItemResponse object
const createResponse = await users.createOne(newUser) // => Promise<ItemResponse<T>>
console.log(createResponse.resource)  // user object returned from create, with CosmosDB-added values

const updateUserResponse = await users.updateOne(thisUser) // => Promise<ItemResponse<T>>

const updatePartialResponse = await users.updateOnePartial(id, {firstName: "Bob"}) // => Promise<ItemResponse<T>>
console.log(updatePartialResponse.resource) // full user object from DB after updates