Lambda(SAM)からAmazon SNSトピックへpublishを行う方法メモ #AWS

LocalStack上で動くAmazon SNSのトピックに対して、AWS SAM CLIで動くLambdaからpublishを行う方法をメモする。

構成

LocalStack準備

docker-compose.yml

  version: "3.8"
  networks:
    container-link:
      name: docker.internal
  services:
    localstack:
      container_name: "${LOCALSTACK_DOCKER_NAME-localstack_main}"
      image: localstack/localstack
      ports:
        - "127.0.0.1:53:53"                # only required for Pro
        - "127.0.0.1:53:53/udp"            # only required for Pro
        - "127.0.0.1:443:443"              # only required for Pro
        - "127.0.0.1:4510-4530:4510-4530"  # only required for Pro
        - "127.0.0.1:4566:4566"
        - "127.0.0.1:4571:4571"
      environment:
        - SERVICES=${SERVICES- }
        - DEBUG=${DEBUG- }
        - DATA_DIR=${DATA_DIR- }
        - LAMBDA_EXECUTOR=${LAMBDA_EXECUTOR- }
        - LOCALSTACK_API_KEY=${LOCALSTACK_API_KEY- }  # only required for Pro
        - HOST_TMP_FOLDER=${TMPDIR:-/tmp/}localstack
        - DOCKER_HOST=unix:///var/run/docker.sock
      volumes:
        - "${TMPDIR:-/tmp}/localstack:/tmp/localstack"
        - "/var/run/docker.sock:/var/run/docker.sock"
      networks:
        - container-link

起動

  docker-compose up

SNS準備

トピックの作成

aws sns create-topic --name test-topic --endpoint-url http://localhost:4566 --profile localstack 
{
    "TopicArn": "arn:aws:sns:ap-northeast-1:000000000000:test-topic"
}

トピックへのサブスクライブ

email プロトコルと notification-endpoint の E メールアドレスを指定する。

aws sns subscribe --topic-arn arn:aws:sns:ap-northeast-1:000000000000:test-topic --protocol email --notification-endpoint test@example.com --endpoint-url http://localhost:4566 --profile localstack 
{
    "SubscriptionArn": "arn:aws:sns:ap-northeast-1:000000000000:test-topic:36e4e475-b360-4c7a-96f0-0690371e7566"
}

Lambda準備

ひな形作成

  sam init

※ランタイムはPython3.8を選択。

template.yml

Hello World Exampleを利用する。
/topic/subscribe(サブスクライブ用)と/topic/publish(パブリッシュ用)を設定するように以下修正

Events:
        PublishTopic:
          Type: Api # More info about API Event Source: https://github.com/awslabs/serverless-application-model/blob/master/versions/2016-10-31.md#api
          Properties:
            Path: /topic/publish
            Method: post

requrements.txt

  requests
  boto3

※SNSアクセス用にboto3追加

Lambda処理(app.py)修正

  import json
  from boto3.session import Session

  # TopicARN
  TOPIC_ARN = u'arn:aws:sns:ap-northeast-1:000000000000:test-topic'

  # SNS 接続設定
  session = Session(
      aws_access_key_id='dummy',
      aws_secret_access_key='dummy',
      region_name='ap-northeast-1'
  )
  client = session.client(
      service_name='sns', 
      endpoint_url='http://localstack:4566'
  )


  def lambda_handler(event, context):
      # メッセージpublish
      request = {
          'TopicArn': TOPIC_ARN,
          'Message': json.loads(event["body"])["msg"],
          'Subject': json.loads(event["body"])["subject"]
      }
      response = client.publish(**request)

      return {
          "statusCode": 200,
          "body": json.dumps({"MessageId":response["MessageId"]}),
      }

動作確認

ビルド

  sam build

実行

  sam local start-api --docker-network docker.internal

メッセージPublish

リクエスト

POST /topic/publish HTTP/1.1
Host: localhost:3000
Content-Type: application/json
Content-Length: 61
{    
  "msg":"test message",    
  "subject":"test subject"
}

レスポンス

{
    "MessageId": "e08bba69-1ceb-4eef-9b88-19f74529bcbf"
}

参考情報

boto3を使ってAmazon SNSへpublishしてみた