This example shows simplified billing system in serverless architecture.

Comprehensive guide describing exactly the architecture, applied design patterns and technologies can be found on our blog in article Simplified billing system with AWS Lambda. Comparision: Kotlin + Micronaut vs Kotlin + Dagger vs vanilla Kotlin.

We encourage you to read, because in this README there is only a substitute for all information.

1. User uploads CSV file (with name structure CLIENTCODE_YEAR_MONTH_activeList.txt) with Beneficiaries (the sample file is located in the data-examples folder) to a specific data storage - asc-lab-serverless-input S3 Bucket.

2. The above action triggers a function (GenerateBillingItemsFunc) that is responsible for:

   • generating billing items (using prices from an external database - PriceList table in DynamoDB) and saving them in the table BillingItem;
   • sending message about the need to create a new invoice to invoice-generation-request-queue;

3. When a new message appears on the invoice-generation-request-queue, next function is triggered (GenerateInvoiceFunc). This function creates domain object Invoice and save this object in database (DynamoDB Invoices table) and send message to queues: invoice-print-request-queue and invoice-notification-request-queue.

4. When a new message appears on the invoice-print-request-queue, function PrintInvoiceFunc is triggered. This function uses external engine to PDF generation - JsReport and saves PDF file in asc-lab-serverless-printout S3 Bucket.

5. When a new message appears on the invoice-notification-request-queue, function NotifyInvoiceFunc is triggered. This function uses two external systems - SendGrid to email sending and Twilio to SMS sending.

Preparation

Deployment requires AWS CLI and Terraform

Before first deployment you need to initialize Terraform with

init.sh

Also you need to create some external accounts and informations

1. jsreportonline (https://jsreportonline.net/) - just username and password
2. SendGrid (https://sendgrid.com/) - API key
3. Twilio (https://www.twilio.com/) - Account SID and Auth Token

As a last step, you need to create variables file to give all the above information to Terraform. Create file billing.tfvars in main folder insides should looks like this:

jsreport_url = "https://some_user.jsreportonline.net/api/report"
jsreport_username = "some_user"
jsreport_password = "some_password"
sendgrid_api_key = "SG.rePNAA_AAAAaAA1aAAAi6w.r5AAAUZhyaaaUo7w0030MFAauAaTWvXw-n11mpAaqe0"
twilio_account_sid = "ACd111feb1c11f11111111cd1dd1111c11"
twilio_auth_token = "1ed1a11111b1af1111b111d1111dd11d"

Building and Deployment

Terraform should create all necessary infrastructure (S3 bucket, SQS Queues, DynamoDB Tables (with data)) and deploy lambdas code.

buildAndDeploy.sh

Testing

You should see S3 Bucket called asc-lab-serverless-input. Put there sample file and enjoy logs in AWS CloudWatch.

Disabling

SQS triggers can actively check queues for new messages. If you don't want to exceed your free tier, you can disable them using our Terraform configuration. Just run:

terraform apply -auto-approve -var-file="billing.tfvars" -var "active=false" terraform

To re-enable triggers run:

terraform apply -auto-approve -var-file="billing.tfvars" -var "active=true" terraform