Apollo AWS Lambda with GraphQL subscriptions

⚠️ This documentation is currently for 1.0.0-alpha.X package which supports only subscriptions-transport-ws and drops the legacy protocol and client support! To use old version that supports legacy protocol and client see the link 0.13.0 below.

📖Documentation for aws-lambda-graphql0.13.0

Use Apollo Server Lambda with GraphQL subscriptions over WebSocket (AWS API Gateway v2).

With this library you can do:

same things as with apollo-server-lambda by utiizing AWS API Gateway v1
GraphQL subscriptions over WebSocket by utilizing AWS API Gateway v2 and subscriptions-transport-ws

Quick start
Packages
- aws-lambda-graphql package
  - Installation
  - Usage
  - API
  - Examples
Infrastructure
Examples

Quick start

In this quick example we're going to build a simple broadcasting server that broadcasts messages received using broadcastMessage mutation to all subscribed connections.

Skip to final implementation if you don't need a step by step guide

1. Create a server

First we need to install dependencies:

yarn add aws-lambda-graphql graphql graphql-subscriptions aws-sdk
# or
npm install aws-lambda-graphql graphql graphql-subscriptions aws-sdk

Note that aws-sdk is required only for local development, it's provided by the AWS Lambda by default when you deploy the app

Now we have all the dependencies installed so lets start with server implementation.

1.1 Setting up Connection and Subscription management

Our GraphQL server needs to know how to store connections and subscriptions because Lambdas are stateless. In order to do that we need create instances of the Connection manager and Subscription manager. In this example we'll leverage DynamoDB as persistent store for our connections and subscriptions.

import {
  DynamoDBConnectionManager,
  DynamoDBSubscriptionManager,
} from 'aws-lambda-graphql';

const subscriptionManager = new DynamoDBSubscriptionManager();
const connectionManager = new DynamoDBConnectionManager({
  subscriptionManager,
});

1.2 Setting up an Event store

In order to be able to broadcast messages (publish events) we need an Event store. Because our server can received a lot of messages we need to work with events in async, meaning that the actual events are not published directly from mutation but rather they are stored in underlying data store which works as an event source for our server. Because we decided to use DynamoDB as our persistent store, we are goint to use it as our event source.

import {
  DynamoDBConnectionManager,
  DynamoDBEventStore,
  DynamoDBSubscriptionManager,
} from 'aws-lambda-graphql';

const eventStore = new DynamoDBEventStore();
const subscriptionManager = new DynamoDBSubscriptionManager();
const connectionManager = new DynamoDBConnectionManager({
  subscriptionManager,
});

That's it for now. Our eventStore will use DynamoDB to store messages that we want to broadcast to all subscribed clients.

1.3 Setting up the GraphQL schema

Our server needs a GraphQL schema. So we'll create one.

import {
  DynamoDBConnectionManager,
  DynamoDBEventStore,
  DynamoDBSubscriptionManager,
} from 'aws-lambda-graphql';

const eventStore = new DynamoDBEventStore();
const subscriptionManager = new DynamoDBSubscriptionManager();
const connectionManager = new DynamoDBConnectionManager({
  subscriptionManager,
});

const typeDefs = /* GraphQL */ `
  type Mutation {
    broadcastMessage(message: String!): String!
  }

  type Query {
    """
    Dummy query so out server won't fail during instantiation
    """
    dummy: String!
  }

  type Subscription {
    messageBroadcast: String!
  }
`;

From given schema we already see that we need to somehow publish and process broadcasted message. For that purpose we must create a PubSub instance that uses our DynamoDB event store as underlying storage for events.

1.4 Create a PubSub instance

PubSub is responsible for publishing events and subscribing to events. Anyone can broadcast message using broadcastMessage mutation (publish) and anyone connected over WebSocket can subscribed to messageBroadcast subscription (subscribing) to receive broadcasted messages.

import {
  DynamoDBConnectionManager,
  DynamoDBEventStore,
  DynamoDBSubscriptionManager,
  PubSub,
} from 'aws-lambda-graphql';

const eventStore = new DynamoDBEventStore();
const subscriptionManager = new DynamoDBSubscriptionManager();
const connectionManager = new DynamoDBConnectionManager({
  subscriptionManager,
});
const pubSub = new PubSub({ eventStore });

const typeDefs = /* GraphQL */ `
  type Mutation {
      broadcastMessage(message: String!): String!
    }

    type Query {
      """
      Dummy query so out server won't fail during instantiation
      """
      dummy: String!
    }

    type Subscription {
      messageBroadcast: String!
    }
`;

const resolvers: {
  Mutation: {
    broadcastMessage: async (
      root,
      { message },
    ) => {
      await pubSub.publish('NEW_MESSAGE', { message });

      return message;
    },
  },
  Query: {
    dummy: () => 'dummy',
  },
  Subscription: {
    messageBroadcast: {
      // rootValue is same as the event published above ({ message: string })
      // but our subscription should return just a string, so we're going to use resolve
      // to extract message from an event
      resolve: rootValue => rootValue.message,
      subscribe: pubSub.subscribe('NEW_MESSAGE'),
    },
  },
};

Our GraphQL schema is now finished. Now we can instantiate the server so we can actually process HTTP and WebSocket events received by our Lambda server and send messages to subscribed clients.

1.5 Create WebSocket/HTTP event handlers and event processor handler

In order to send messages to subscribed clients we need the last piece and it is a Event processor. Event processor is responsible for processing events published to our Event store and sending them to all connections that are subscribed for given event.

Because we use DynamoDB as an event store, we are going to use DynamoDBEventProcessor.

import {
  DynamoDBConnectionManager,
  DynamoDBEventProcessor,
  DynamoDBEventStore,
  DynamoDBSubscriptionManager,
  PubSub,
  Server,
} from 'aws-lambda-graphql';

const eventStore = new DynamoDBEventStore();
const eventProcessor = new DynamoDBEventProcessor();
const subscriptionManager = new DynamoDBSubscriptionManager();
const connectionManager = new DynamoDBConnectionManager({
  subscriptionManager,
});
const pubSub = new PubSub({ eventStore });

const typeDefs = /* GraphQL */ `
  type Mutation {
      broadcastMessage(message: String!): String!
    }

    type Query {
      """
      Dummy query so out server won't fail during instantiation
      """
      dummy: String!
    }

    type Subscription {
      messageBroadcast: String!
    }
`;

const resolvers: {
  Mutation: {
    broadcastMessage: async (
      root,
      { message },
    ) => {
      await pubSub.publish('NEW_MESSAGE', { message });

      return message;
    },
  },
  Query: {
    dummy: () => 'dummy',
  },
  Subscription: {
    messageBroadcast: {
      // rootValue is same as the event published above ({ message: string })
      // but our subscription should return just a string, so we're going to use resolve
      // to extract message from an event
      resolve: rootValue => rootValue.message,
      subscribe: pubSub.subscribe('NEW_MESSAGE'),
    },
  },
};

const server = new Server({
  // accepts all the apollo-server-lambda options and adds few extra options
  // provided by this package
  connectionManager,
  eventProcessor,
  resolvers,
  subscriptionManager,
  typeDefs,
});

export const handleWebSocket = server.createWebSocketHandler();
export const handleHTTP = server.createHttpHandler();
// this creates dynamodb event handler so we can send messages to subscribed clients
export const handleEvents = server.createEventHandler();

Now our server is finished.

You need to map:

ApiGateway v2 events to handleWebSocket handler
ApiGateway v1 events to handleHTTP
DynamoDB stream from events table to handleEvents.

In order to do that you can use Serverless framework, see serverless.yml file.

To connect to this server you can use Apollo Client + subscriptions-transport-ts - see example in section 2

1.6 Pass PubSub to resolvers using GraphQL context

Sometime if you have complex schema you want to pass dependencies using context so it's easier to manage.

import {
  DynamoDBConnectionManager,
  DynamoDBEventProcessor,
  DynamoDBEventStore,
  DynamoDBSubscriptionManager,
  PubSub,
  Server,
} from 'aws-lambda-graphql';

const eventStore = new DynamoDBEventStore();
const eventProcessor = new DynamoDBEventProcessor();
const subscriptionManager = new DynamoDBSubscriptionManager();
const connectionManager = new DynamoDBConnectionManager({
  subscriptionManager,
});
const pubSub = new PubSub({ eventStore });

const typeDefs = /* GraphQL */ `
  type Mutation {
      broadcastMessage(message: String!): String!
    }

    type Query {
      """
      Dummy query so out server won't fail during instantiation
      """
      dummy: String!
    }

    type Subscription {
      messageBroadcast: String!
    }
`;

const resolvers: {
  Mutation: {
    broadcastMessage: async (
      root,
      { message },
      ctx,
    ) => {
      await ctx.pubSub.publish('NEW_MESSAGE', { message });

      return message;
    },
  },
  Query: {
    dummy: () => 'dummy',
  },
  Subscription: {
    messageBroadcast: {
      resolve: rootValue => rootValue.message,
      // subscribe works similarly as resolve in any other GraphQL type
      // pubSub.subscribe() returns a resolver so we need to pass it all the args as were received
      // so we can be sure that everything works correctly internally
      subscribe: (rootValue, args, ctx, info) => {
        return ctx.pubSub.subscribe('NEW_MESSAGE')(rootValue, args, ctx, info);
      },
    },
  },
};

const server = new Server({
  // accepts all the apollo-server-lambda options and adds few extra options
  // provided by this package
  context: {
    pubSub,
  },
  connectionManager,
  eventProcessor,
  resolvers,
  subscriptionManager,
  typeDefs,
});

export const handleWebSocket = server.createWebSocketHandler();
export const handleHTTP = server.createHttpHandler();
// this creates dynamodb event handler so we can send messages to subscribed clients
export const handleEvents = server.createEventHandler();

2 Connect to the server using Apollo Client and `subscriptions-transport-ts`

First install dependencies

yarn add apollo-link-ws apollo-cache-inmemory apollo-client subscriptions-transport-ws
# or
npm install apollo-link-ws apollo-cache-inmemory apollo-client subscriptions-transport-ws

import { WebSocketLink } from 'apollo-link-ws';
import { InMemoryCache } from 'apollo-cache-inmemory';
import { ApolloClient } from 'apollo-client';
import { SubscriptionClient } from 'subscriptions-transport-ws';

const wsClient = new SubscriptionClient(
  'ws://localhost:8000', // please provide the uri of the api gateway v2 endpoint
  { lazy: true, reconnect: true },
  null,
  [],
);
const link = new WebSocketLink(wsClient);
const client = new ApolloClient({
  cache: new InMemoryCache(),
  link,
});

3 Deploy and development

3.1 Serverless support

To deploy your api created using this library please see serverless.yml template of example app.

3.2 Serverless-offline support

This library supports serverless-offline. But you have to do small changes in your code to actually support it, it's not automatical.

You need to set up custom endpoint for ApiGatewayManagementApi and custom endpoint for DynamoDB if you're using it. Please refer to chat-example-server source code.

Packages

aws-lambda-graphql package

GraphQL client and server implementation for AWS Lambda.

See package

Infrastructure

Current infrastructure is implemented using AWS Lambda + AWS API Gateway v2 + AWS DynamoDB (with DynamoDB streams). But it can be implemented using various solutions (Kinesis, etc) because it's written to be modular.

Examples

Chat App - React app
Chat Server
- contains AWS Lambda that handles HTTP, WebSocket and DynamoDB streams
- also includes serverless.yml file for easy deployment