nim-app

Containerized sample Nim application powered by Prologue.

We deploy the application to AWS App Runner and proxy traffic to it via Cloudflare.

Build and run locally

docker build -t nim-app:v1 .
docker run --init -it -p 8080:8080 --rm nim-app:v1

Host the app with AWS App Runner (public endpoint)

⚠️ This guide is a work in progress, and may be incomplete

ℹ️ This requires an AWS account and will incur some App Runner and ECR costs.

1. Create AWS ECR repository to host the container images

   ℹ️ We configure ECR image tags as MUTABLE, to leverage the App Runner autodeployment feature

   aws cloudformation deploy --template-file aws/ecr-repo.yml --stack-name nim-app-ecr --parameter-overrides Name=nim-app
   ecr_repository="$(aws cloudformation describe-stacks --stack-name nim-app-ecr | jq -r '.Stacks[0].Outputs[] | select(.OutputKey == "Uri") | .OutputValue')"
   ecr_registry="${ecr_repository%%/nim-app}"

2. Build, tag and push the docker image to the ECR repository

   aws ecr get-login-password | docker login --username AWS --password-stdin $ecr_registry
   docker build -t nim-app:v1 .
   docker tag nim-app:v1 $ecr_repository:v1
   docker push $ecr_repository:v1

3. Deploy the app as AWS App Runner service

   ℹ️ We create the autoscaling configuration using AWS CLI, because CloudFormation does not yet support this functionality

   autoscaling_config_arn="$(aws apprunner create-auto-scaling-configuration --auto-scaling-configuration-name nim-app \
       --max-concurrency 100 --min-size 1 --max-size 2 | jq -r '.AutoScalingConfiguration.AutoScalingConfigurationArn')"
   aws cloudformation deploy --template-file aws/app-runner.yml --capabilities CAPABILITY_NAMED_IAM \
       --stack-name nim-app-runner --parameter-overrides Image="$ecr_repository:v1" AutoScalingConfigArn=$autoscaling_config_arn
   service_arn="$(aws cloudformation describe-stacks --stack-name nim-app-runner | jq -r '.Stacks[0].Outputs[] | select(.OutputKey == "Arn") | .OutputValue')"
   echo "Service URL: https://$(aws cloudformation describe-stacks --stack-name nim-app-runner | jq -r '.Stacks[0].Outputs[] | select(.OutputKey == "Url") | .OutputValue')"

4. Try changing the hello handler code in src/app.nim, then build, tag and push the v1 image again, and observe result

Proxy traffic to the App Runner service through Cloudflare

This requires a Cloudflare account and website.

1. Associate custom DNS domain (e.g. app.example.com) to the App Runner service

   ℹ️ We use AWS CLI here, because CloudFormation does not yet support this functionality

   aws apprunner associate-custom-domain --service-arn $service_arn --domain-name <domain> --no-enable-www-subdomain
   aws apprunner describe-custom-domains --service-arn $service_arn | jq -r '.CustomDomains[0].CertificateValidationRecords[]'

2. Create DNS records in Cloudflare DNS and configure SSL/TLS

   • Login to Cloudflare dashboard
   • Navigate to <website> → DNS → Records
   • Select Add record and create a DNS Only CNAME record for all the validation records from step 1
   • Select Add record and create a Proxied (orange clouded) CNAME record for <domain>, pointing to the App Runner service URL
   • Navigate to <website> → SSL/TLS → Overview
   • Ensure that encryption mode is Full (strict)

3. Test the app at https://<domain

Tear down all resources

1. Delete Cloudflare DNS records

   • Login to Cloudflare dashboard
   • Navigate to <website> → DNS → Records
   • Delete the associated certificate validation and proxy CNAME records

2. Remove AWS resources

   aws cloudformation delete-stack --stack-name nim-app-runner
   aws cloudformation wait stack-delete-complete --stack-name nim-app-runner
   aws apprunner delete-auto-scaling-configuration --auto-scaling-configuration-arn $autoscaling_config_arn
   for digest in $(aws ecr list-images --repository-name nim-app | jq -r '.imageIds[].imageDigest'); do
       aws ecr batch-delete-image --repository-name nim-app --image-ids imageDigest=$digest
   done
   aws cloudformation delete-stack --stack-name nim-app-ecr
   aws cloudformation wait stack-delete-complete --stack-name nim-app-ecr

TODOs

• Explore use of AWS C++ SDK from Nim (calling e.g. DynamoDB)
  • https://nim-lang.org/docs/manual.html#implementation-specific-pragmas-importcpp-pragma