Email Status

This project implements the scenario that an email goes out via Mailgun (mailgun.com). Once it’s out, Mailgun sends various events back (open, clicked, etc). We have sent an email via Mailgun and now we expect those events sent to us via webhooks, hitting an API Gateway and then that information is proxied to a Lambda. The Lambda should do two things: save a copy of the raw webhook and publish a transformed version into SNS.

This project has been generated using the aws-nodejs-typescript template from the Serverless framework.

For detailed instructions, please refer to the documentation.

Installation/deployment instructions

Clone this repository to your local machine by running the git clone https://github.com/GwamakaCharles/email-status.git command

Depending on your preferred package manager, follow the instructions below to deploy your project.

Requirements: NodeJS lts/fermium (v.14.15.0). If you're using nvm, run nvm use to ensure you're using the same Node version in local and in your lambda's runtime.

Using NPM

• Run npm i to install the project dependencies

Using Yarn

• Run yarn to install the project dependencies

Configurations

⚠️ WARNING
It is important to change configuration settings before building, packaging and deployment.

This project by default deploys to us-east-1 to change it, add --region [REGION_NAME] when building and deploying

:info: INFO
The SNS service is deployed to us-east-1, change to this region to see cloudwatch logs

Go to the src/functions/db.ts file to change Mongodb database configuration parameters to deploy with your own database

Storing Secrets and Keys

For security, this guide will help to store secrets using Parameter Store provided by Systems Manager in AWS.

These keys need to be stored on AWS as the Lambda functions will need them to run.

To store a key, make sure you are authenticated via the AWS CLI and run the following command:

aws ssm put-parameter --name NAME_OF_SECRET \
                      --value 'my super safe secret' \
                      --type SecureString

Below are the keys needed to run these lambda functions:

AccountId="xxxxxxxxxxx" (This is your AWS account ID)

MAILGUN_API_KEY="XXXXXXXXXXXXXXX" (API key from Mailgun)

MAILGUN_DOMAIN="mailgun.XXXXXXXX.com" (Domain on mailgun)

Deployment

• Connect to AWS from AWS CLI from your teminal by using the aws configure command.
• Run npx sls package --package dist to build from typescript to javascript files and package it in to the dist folder with cloudformation configuration files
• Run npx sls deploy --package dist to deploy this stack to AWS

NOTE:: This project by default deploys to us-east-1 to build and deploy to othe regions, add --region [REGION_NAME] flag when building and deploying

Alternatively: You can also install the serverless package globally by runing npm install -g serverless and then, run the npm run build-deploy command to both build and deploy to AWS

Testing the service

This template contains a two lambda functions triggered by an HTTP request made on the provisioned API Gateway REST API /sendEmail and /webhook routes with POST method. The request body must be provided as application/json. The body structure is tested by API Gateway against src/functions/sendEmail/schema.ts and src/functions/webhook/schema.ts JSON-Schema definitions: must contain the from, to, subject, html and event-data, signature properties respectively.

• requesting any other path than /sendEmail or /webhook with any other method than POST will result in API Gateway returning a 404 HTTP error code
• sending a POST request to /sendEmail or /webhook with a payload not containing the reuqired string properties will result in API Gateway returning a 400 HTTP error code
• sending a POST request to /sendEmail or /webhook with a payload containing the required string properteis will result in API Gateway returning a 200 HTTP status code.

Locally

In order to test the sendEmail and webhook functions locally, run the following command:

• npx sls invoke local -f sendEmail --path src/functions/sendEmail/mock.json if you're using NPM

• yarn sls invoke local -f sendEmail --path src/functions/sendEmail/mock.json if you're using Yarn

• npx sls invoke local -f webhook --path src/functions/webhook/mock.json if you're using NPM

• yarn sls invoke local -f webhook --path src/functions/webhook/mock.json if you're using Yarn

Check the sls invoke local command documentation for more information.

Remotely

Two API endpoints will be generated after the deployment, found after running npx sls deploy command. Output should be in the format

• https://ApiEndpoint/dev/sendEmail - This is the endpoint for sending email.

• https://ApiEndpoint/dev/webhook - This webhook should be configured on your mailgun account to send events (e.g opened, delivered, click e.t.c)

Copy and replace your url - found in Serverless deploy command output - and from, to, subject, html parameters in the following curl command in your terminal or in Postman to test your newly deployed application.

curl --location --request POST 'https://ApiEndpoint/dev/sendEmail' \
--header 'Content-Type: application/json' \
--data-raw '{
    "to": ["[email protected]"],
    "from": "[email protected]", # Sender's email from your mailgun account
    "subject": "Email Service"
    "html":"This is a test email from email service" # Body of the email
}'

⚠️ As is, this template, once deployed, opens a public endpoint within your AWS account resources. Anybody with the URL can actively execute the API Gateway endpoint and the corresponding lambda.

Project structure

The project code base is mainly located within the src folder. This folder is divided in:

• functions - containing code base and configuration for the lambda functions
• libs - containing shared code base between lambdas

.
├── src
│   ├── functions               # Lambda configuration and source code folder
│   │   ├── sendEmail
│   │   │   ├── handler.ts      # `sendEmail` lambda source code
│   │   │   ├── index.ts        # `sendEmail` lambda Serverless configuration
│   │   │   ├── mock.json       # `sendEmail` lambda input parameter, if any, for local invocation
│   │   │   └── schema.ts       # `sendEmail` lambda input event JSON-Schema
│   │   ├── webhook
│   │   │   ├── handler.ts      # `webhook` lambda source code
│   │   │   ├── index.ts        # `webhook` lambda Serverless configuration
│   │   │   ├── mock.json       # `webhook` lambda input parameter, if any, for local invocation
│   │   │   └── schema.ts       # `webhook` lambda input event JSON-Schema
│   │   │
│   │   ├── keyStoreModule.ts   # This module connects to stored secrets and keys using Parameter Store provided by Systems Manager in AWS.
│   │   ├── db.ts               # mongodb database connection abstactions.
│   │   └── index.ts            # Import/export of all lambda configurations
│   │
│   └── libs                    # Lambda shared code
│       └── apiGateway.ts       # API Gateway specific helpers
│       └── handlerResolver.ts  # Sharable library for resolving lambda handlers
│       └── lambda.ts           # Lambda middleware
│
├── package.json
├── serverless.ts               # Serverless service file
├── tsconfig.json               # Typescript compiler configuration
├── tsconfig.paths.json         # Typescript paths
└── webpack.config.js           # Webpack configuration

3rd party libraries

• json-schema-to-ts - uses JSON-Schema definitions used by API Gateway for HTTP request validation to statically generate TypeScript types in your lambda's handler code base
• middy - middleware engine for Node.Js lambda. This template uses http-json-body-parser to convert API Gateway event.body property, originally passed as a stringified JSON, to its corresponding parsed object
• @serverless/typescript - provides up-to-date TypeScript definitions for your serverless.ts service file