aws-signup-notifications

Listen to SNS topic about signup events to organization. Send this event to REST endpoint together with information about other users that joined recently.

Prerequisites

Below instructions were tested on WSL2 - Ubuntu

Install Terraform

Use Ubuntu instructions from https://www.terraform.io/downloads

curl -fsSL https://apt.releases.hashicorp.com/gpg | sudo apt-key add -
sudo apt-add-repository "deb [arch=amd64] https://apt.releases.hashicorp.com $(lsb_release -cs) main"
sudo apt-get update && sudo apt-get install terraform

Verify installation. You shoud see something like:

terraform -v
Terraform v1.1.4
on linux_amd64

AWS CLI

Install

Install AWS CLI

sudo apt install awscli

Verify installation

aws --version

Configure

aws configure

Solution Architecture

Lambda functions are implemented in Java 8. Whole infrastructure and Lambda functions deployment is implemented with Terraform.

Below are main AWS resources used in this solution, listed in order of data flow.

AWS Resource	Name	Purpose
SQS queue	signups_queue	This queue is subscribed to SNS topic. In this way all notifications are put on the queue and no events are lost.
Lambda (Java)	signups_processing_function	Triggered by events from signups_queue. In 5 element batches.
DynamoDB table	Signups	Keeps signup events. Used to collect recent joiners in case signup_processing_function gets a batch of less than 4 records.
SQS queue	welcome_notifications_queue.fifo	Gets welcome notification events, deduplicated by notification receiver id. FIFO queue to enforce exactly-once processing
Lambda (Java)	notifications_sender_function	Triggered by events from welcome_notifications_queue.fifo in batch of 1 record. Sends notifications to REST endpoints. Tries 3 times in case of non 2xx response, then execution fails and new event is triggered again.

Deployment

Build Lambda Functions

In project root directory run

mvn clean install

Terraform deployment

Initialize Terraform

In project root directory run

cd terraform
terraform init

Export secret variables

export TF_VAR_sns_signups_arn=<ARN of SNS topic with signup events>
export TF_VAR_lambda_env_notification_joined_organization=<Name of organization/site/etc which users joined>
export TF_VAR_lambda_env_notification_sender=<Email address of notifications sender>
export TF_VAR_lambda_env_notification_rest=<REST endpoint for posting notification events>

Deploy infrastructure

To see planned changes run

terraform plan

To execute actual deployment run

terraform apply

Destroy resources

terraform destroy