12/09 Amazon API Gateway WebSocket API

2 min read

この記事は、Serverless Hello World Advent Calendar 2020の9日目です。

Amazon API GatewayとAWS Lambdaを使ってWebSocket APIを実装します。

サービスの作成

WebSocket APIのテンプレートはないので、Websocketイベントのページを見ながらごりごり書いていきます。

serverless.yml
service: serverless-helloworld

provider:
  name: aws
  runtime: nodejs12.x
  region: ap-northeast-1

functions:
  default:
    handler: handler.default
    events:
      - websocket: $default
handler.js
'use strict';

const AWS = require('aws-sdk');
AWS.config.update({ region: process.env.AWS_REGION });

module.exports.default = async (event, context) => {
  const client = new AWS.ApiGatewayManagementApi({
    apiVersion: '2018-11-29',
    endpoint: `https://${event.requestContext.domainName}/${event.requestContext.stage}`,
  });

  await client
    .postToConnection({
      ConnectionId: event.requestContext.connectionId,
      Data: `Hello ${event.body || 'World'}!`,
    })
    .promise();

  return {
    statusCode: 200,
  };
};
.gitignore
# package directories
node_modules
jspm_packages

# Serverless directories
.serverless

デプロイ

ではデプロイします。

$ sls deploy
Serverless: Packaging service...
Serverless: Excluding development dependencies...
Serverless: Creating Stack...
Serverless: Checking Stack create progress...
........
Serverless: Stack create finished...
Serverless: Uploading CloudFormation file to S3...
Serverless: Uploading artifacts...
Serverless: Uploading service serverless-helloworld.zip file to S3 (483 B)...
Serverless: Validating template...
Serverless: Updating Stack...
Serverless: Checking Stack update progress...
.................................
Serverless: Stack update finished...
Service Information
service: serverless-helloworld
stage: dev
region: ap-northeast-1
stack: serverless-helloworld-dev
resources: 12
api keys:
  None
endpoints:
  wss://o92hsw0jf6.execute-api.ap-northeast-1.amazonaws.com/dev
functions:
  default: serverless-helloworld-dev-default
layers:
  None

動作確認

今回はWebSocketなので、wscatを使って動作確認します。

$ npm install -g wscat
$ wscat -c wss://o92hsw0jf6.execute-api.ap-northeast-1.amazonaws.com/dev
Connected (press CTRL+C to quit)
> 
< Hello World!
> world
< Hello world!
> ^C

WebSocket APIとして動いていることが確認できました。

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