Daniele Salvagni - aws notes

Lambda

Lambda Log Retention

Resources:
  Function:
    Type: AWS::Serverless::Function
    Properties: ...

  LogGroup:
    Type: AWS::Logs::LogGroup
    Properties:
      LogGroupName: !Sub "/aws/lambda/${Function}"
      RetentionInDays: 7

It looks like this won’t be changed any time soon: GitHub Issue

Typescript Lambda (API Gateway Proxy)

Typescript boilerplate

import { APIGatewayProxyEvent, APIGatewayProxyResult } from "aws-lambda";

export const lambdaHandler = async (
  event: APIGatewayProxyEvent,
): Promise<APIGatewayProxyResult> => {
  // ...
};

SAM CloudFormation Template

Resources:
  GetItemByIdFunction:
    Type: AWS::Serverless::Function
    Metadata:
      BuildMethod: esbuild
      BuildProperties:
        Minify: false
        Target: es2020
        EntryPoints:
          - app.ts
        External: # to be found in the dependency layer, will not be bundled
          - "@aws-sdk/client-dynamodb"
          - "@aws-sdk/lib-dynamodb"
    Properties:
      CodeUri: functions/getItemById
      Description: Get an item by id from a DynamoDB table
      Environment:
        Variables:
          SAMPLE_TABLE: !Ref SampleTable
      Handler: app.lambdaHandler
      Layers:
        - !Ref DependencyLayer
      Policies:
        - DynamoDBCrudPolicy:
            TableName: !Ref SampleTable
      Events:
        Api:
          Type: Api
          Properties:
            Path: /{id}
            Method: GET

EventBridge Event type definition

Example of an EventBridge event type definition for an S3 Object Created event (the documentation currently lacks on this topic)

import {
  EventBridgeEvent,
  S3ObjectCreatedNotificationEventDetail,
} from "aws-lambda";

export const handler = async (
  event: EventBridgeEvent<
    "Object Created",
    S3ObjectCreatedNotificationEventDetail
  >,
): Promise<void> => {
  console.log("event: ", JSON.stringify(event, null, 2));
};

CloudFront Functions

CloudFront Functions’ JavaScript runtime does not support exports, here is a simple workaround:

async function handler(event) {
  // ...
}

var module = module || {};
module.exports = { handler };

Elastic Load Balancer Target Group naming

If an update triggers a replacement of a Load Balancer, it could error with Target group 'arn:aws:...' cannot be associated with more than one load balancer