AeroReserve Payment Service

This project contains source code and supporting files for the payment service, a serverless application that you can deploy with the SAM CLI. It includes the following files and folders.

lambda-function - Code for the application's Lambda function.
events - Invocation events that you can use to invoke the function.
lambda-function/tests - Unit tests for the application code.
template.yaml - A template that defines the application's AWS resources.

The application uses several AWS resources, including Lambda functions and an EventBridge rule. These resources are defined in the template.yaml file in this project. You can update the template to add AWS resources through the same deployment process that updates your application code.

When an event is received by the EventBridge rule (which collects AMQP messages from the message broker and forwards them to the Lambda function), the Lambda function is invoked. The function processes the event which contains the payment request id, and then publishes the payment response id to the message broker.

The Lambda function is written in Node.js and uses the amqplib library to interact with the message broker.

A secret called rabbitmq-credentials is used to store the RabbitMQ credentials. The Lambda function retrieves the credentials from the secret to connect to the message broker. It should contain the followin key/value pairs:

username - The username to authenticate with the RabbitMQ server.
password - The password to authenticate with the RabbitMQ server.
host - The hostname of the RabbitMQ server.

Deploy the application to AWS

The Serverless Application Model Command Line Interface (SAM CLI) is an extension of the AWS CLI that adds functionality for building and testing Lambda applications. It uses Docker to run your functions in an Amazon Linux environment that matches Lambda. It can also emulate your application's build environment and API.

To use the SAM CLI, you need the following tools.

SAM CLI - Install the SAM CLI
Node.js - Install Node.js 20, including the NPM package management tool.
Docker - Install Docker community edition

To build and deploy the payment reservation service for the first time, run the following in the shell:

sam build
sam deploy

The first command will build the source of your application. The second command will package and deploy your application to AWS.

We then need to deploy the CodePipeline that will build and deploy the application when changes are made to the source code. First, we have to create the resources needed for the pipeline. To do this, run the following in your shell:

sam pipeline init --bootstrap

A range of questions will be asked to configure the pipeline, do the following:

Select a pipeline template to get started: AWS Quick Start Pipeline Templates (1)
Select CI/CD system: AWS CodePipeline (5)
Which pipeline template would you like to use? Two-stage pipeline (1)
Do you want to go through stage setup process now? [Y/n]: For the rest of the questions, you can press enter to use the default values.

Once this completes the following resources were created in your account:

Pipeline IAM user
Pipeline execution role
CloudFormation execution role
Artifact bucket

For more information on how to deploy the pipeline, see the [AWS SAM Workshop]](https://catalog.workshops.aws/complete-aws-sam/en-US/module-4-cicd/module-4-cicd-codepipeline/50-sampipeinit).

Now you can create a new CloudFormation stack which will set up our CI/CD pipeline. We will use the sam deploy command to launch this new stack.

sam deploy -t codepipeline.yaml --stack-name aeroreserve-payment-service-pipeline --capabilities=CAPABILITY_IAM

Once the aeroreserve-payment-service-pipeline CloudFormation stack has completed, you will have a new CodePipeline pipeline. This pipeline will automatically build and deploy your application whenever you push changes to the source code repository.

Use the SAM CLI to build and test locally

Build your application with the sam build command.

aeroreserve-payment-service$ sam build

The SAM CLI installs dependencies defined in lambda-function/package.json, creates a deployment package, and saves it in the .aws-sam/build folder.

Test the function by invoking it directly with a test event. An event is a JSON document that represents the input that the function receives from the event source. A test is included in the events folder in this project.

Run the function locally and invoke it with the sam local invoke command.

aeroreserve-payment-service$ sam local invoke AeroReservePaymentServiceFunction --event events/event.json

Fetch, tail, and filter Lambda function logs

To simplify troubleshooting, SAM CLI has a command called sam logs. sam logs lets you fetch logs generated by your deployed Lambda function from the command line. In addition to printing the logs on the terminal, this command has several nifty features to help you quickly find the bug.

aeroreserve-payment-service$ sam logs -n AeroReservePaymentServiceFunction --stack-name aeroreserve-payment-service --tail

Unit tests

Tests can be defined in the lambda-function/tests folder in this project. Use NPM to install the Mocha test framework and run unit tests.

aeroreserve-payment-service$ cd lambda-function
lambda-function$ npm install
lambda-function$ npm run test

Cleanup

To delete the application that you created, use the AWS CLI.

sam delete --stack-name aeroreserve-payment-service

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