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serverless-webapp-kotlin

Use Azure Serverless stack to build a full-fledged web application with both backend and frontend hosted inside a same mono repo.

CI/CD pipeline is implemented using GitHub actions for both backend and frontend app including related serverless cloud infrastructure for backend and frontend. Infrastructure as code(IAC) for both frontend and backend infra is written using Bicep

Application builds a React static web app, which talks to a bunch of APIs hosted via Azure API Management and talking to azure functions written in kotlin, Azure storage and Azure Cosmo DB and Azure Cognitive services as backends. Feature of web application itself is simple. Since that is not the main purpose here. User can basically upload an image with a metadata. Then if user want, they can try uploading another image from another flow, and try to find face in it. If it's found in Cosmo DB, then we return the metadata.

Demos:

Architecture diagram for the application

Architecture

Demo

Demo

Pre-requisite

Either install tools listed below or use Github codespaces.

Initialization

Given pre requisite are already configured, lets get started to initialize local environment.

  1. Set environment variables.

    AZURE_TENANT=<<tenant-id>>
SUBSCRIPTION_ID=<<subscription-id>>

AZURE_REGION=<<region>>
RESOURCE_GROUP=<<new resource group name>>

# Required if custom domain needs to be configured for the app, else set as empty
DNS_ZONE=<<custom domain that you own>>

  2. Login into azure

    # Complete login on the browser window which opens up after below command
az login --tenant $AZURE_TENANT
az account set --subscription $SUBSCRIPTION_ID

# Set default resource group and region. If you don't want to set default, make sure to pass this in relevant commands later.
az config set defaults.location=$AZURE_REGION defaults.group=$RESOURCE_GROUP

Deploy core infrastructure resources

  1. In core infra setup, resources which are common to both frontend and backend are deployed. Primarily this is used to create a resource group where both frontend and backend resources will be created. If you plan to configure custom domain name for the app, Azure DNS zone can also be created.

    az deployment sub create -f core/bicep/main.bicep -n core-infra -p resourceGroup=$RESOURCE_GROUP location=$AZURE_REGION dnsZoneName=$DNS_ZONE

  2. !!OPTIONAL!! If DNS Zone is specified for custom domain, update your DNS registrar with created DNS zone name server info. You can get name server info by running below command.

    az network dns zone show --name $DNS_ZONE -o jsonc

Deploy frontend infrastructure and application

  1. Before deploying frontend infrastructure, make sure the subscription is enabled for Microsoft.Cdn namespace.

    az provider register --namespace Microsoft.Cdn

  2. Deploy frontend infrastructure which includes storage account for static website hosting and Azure CDN. Depending on if you specify DNS zone as well, it will attempt to configure custom domain with the CDN as wel with CDN managed certificate. By default, IAC will configure custom domain with app.$DNS_ZONE

    az deployment group create -f frontend/bicep/main.bicep --name app-frontend -p dnsZoneName=$DNS_ZONE

FRONTEND_STORAGE=$(az deployment group show --name app-frontend --output tsv --query 'properties.outputs.storageAccountNameForFrontEndArtifacts.value')

FRONTEND_URL=$(az deployment group show --name app-frontend --output tsv --query 'properties.outputs.cdnEndpointHostName.value')

echo $FRONTEND_STORAGE
echo $FRONTEND_URL

    Next, Go to the azure portal and navigate to Azure CDN endpoint created. Under custom domain, enable custom https and use cdn managed.

    CDN-cert

  3. Deploy frontend application

    cd frontend
npm ci --legacy-peer-deps
npm run build --if-present

az storage blob upload-batch --account-name $FRONTEND_STORAGE --auth-mode key -d '$web' -s build/. --overwrite

cd ..

    At this point the frontend site should be up and running. Navigate to the FRONTEND_URL. If in case, It's still not up, probably CDN purge is required. Execute below command to purge the CDN profile.

    az cdn endpoint purge --content-paths / --ids $(az cdn endpoint list --profile-name $(az cdn profile list -o tsv --query [0].name) -o tsv --query [0].id)

Deploy backend infrastructure and application

Now that the frontend application should be up and running, let get started to deploy the backend infrastructure and application. Backend infrastructure exposes REST apis using Azure API management backed by azure functions. It also uses storage account blob containers to store images and Azure cosmo DB for metadata etc. Azure Cognitive service face api is used to perform recognition.

  1. Deploy backend infrastructure.

    az deployment group create -f backend/bicep/main.bicep --name app-backend -p originHostForFrontend=$FRONTEND_URL createApim=true dnsName=$DNS_ZONE

  2. !!OPTIONAL!! Configure custom domain with APIM Managed Certificate, which is still in public preview. This step is required only if you are using custom domain as well to configure the app. By default, IAC will configure custom domain with api.$DNS_ZONE. Because free managed cert for APIM is still in preview, we need to do perform some steps manually in console.

    Firstly, Navigate to azure portal --> resource group --> configured resource group --> APIM --> Select deployed APIM instance --> go to custom domain. Refer screenshot below. Copy the TXT record has value. Hostname value should be api.$DNS_ZONE. So if you domain name is contosohotels.com then put api.contosohotels.com. Click Add but Do not click save yet. We first need to configure dns records in the dns zone.

    APIM-CertNext, once you have TXT record hash copied, run below command:

    APIM=$(az deployment group show --name app-backend --output tsv --query 'properties.outputs.apiManagementName.value')

echo $APIM

az deployment group create  -f backend/bicep/apimManagedCert.bicep  --name app-backend-apim-cert -p dnsZoneName=$DNS_ZONE apimName=$APIM txtHash=<<Hash fetched from portal>>

    Now head back to the azure portal and click Save to complete custom domain initialization and for APIM to configure and issue free managed cert.

    Note: When configuring custom domain with APIM Managed cert, make sure to run subsequent deployment of backend infra with parameter createApim=false. Since managed cert is still in preview, part of the process has to be enabled manually from console rite now and running creation via ARM replaces manual configuration in APIM.

  3. Deploy the backend application written in kotlin via maven azure function plugin.

    FN_APP_NAME=$(az deployment group show --name app-backend --output tsv --query 'properties.outputs.functionAppName.value')

echo $FN_APP_NAME
mvn clean install -f backend/FaceApp/pom.xml -DappName=$FN_APP_NAME

mvn azure-functions:deploy -f backend/FaceApp/pom.xml -DresourceGroup=$RESOURCE_GROUP -DappName=$FN_APP_NAME

  4. Now that we have all the azure functions deployed, we need to configure event subscription for when any image is created in the image storage blob container it triggers an azure function to process that image.

    IMAGE_STORAGE=$(az deployment group show --name app-backend --output tsv --query 'properties.outputs.imageStorageAccountName.value')

echo $IMAGE_STORAGE

az deployment group create -f backend/bicep/eventSubscription.bicep  --name app-backend-event-subscription -p storageAccountName=$IMAGE_STORAGE functionApp=$FN_APP_NAME devSubscriptionUrl=''

  5. Fetch API related details to update it in the frontend application.

    FIND_IMAGE_URL=$(az deployment group show --name app-backend --output tsv --query 'properties.outputs.findPersonUrl.value')

UPLOAD_URL=$(az deployment group show --name app-backend --output tsv --query 'properties.outputs.uploadURl.value')

APIMID=$(az apim show -n $APIM --query id -o tsv)

CODE=$(az rest --method post  --uri ${APIMID}/subscriptions/face-app-frontend/listSecrets?api-version=2021-08-01 --query primaryKey -o tsv)

echo $FIND_IMAGE_URL
echo $UPLOAD_URL
echo $CODE

  6. Deploy the frontend app again with the update url of the backend APIs. Edit the file GlobalConstants.ts and update properties UPLOAD_URL and FIND_IMAGE in the constants along with code query param.

    cd frontend
npm run build --if-present
  
az storage blob upload-batch --account-name $FRONTEND_STORAGE --auth-mode key -d '$web' -s build/. --overwrite

cd ..

az cdn endpoint purge --content-paths / --ids $(az cdn endpoint list --profile-name $(az cdn profile list -o tsv --query [0].name) -o tsv --query [0].id)

echo $FRONTEND_URL

CONGRATULATIONS!! The application should be up and running with both frontend and backend functional.

Deployment using CI and CD

Application uses GitHub actions for deploying both infrastructure and application resources. All workflows can be found in .github folder.

Git actions uses Azure login action with OpenID Connect to authenticate with azure.

Setup app for OpenId Connect Auth

  1. Register and configure application for GitHub actions deployment.

    appId=$(az ad app create --display-name serverless-webapp-kotlin-oidc --query appId -otsv)

az ad sp create --id $appId --query appId -otsv

objectId=$(az ad app show --id $appId --query id -otsv)

cat <<EOF > body.json
{
    "name": "serverless-webapp-kotlin-federated-identity",
    "issuer": "https://token.actions.githubusercontent.com",
    "subject": "repo:Azure-samples/serverless-webapp-kotlin:ref:refs/heads/main",
    "description": "GitHub account federated identity",
    "audiences": [
        "api://AzureADTokenExchange"
    ]
}
EOF

az rest --method POST --uri "https://graph.microsoft.com/beta/applications/$objectId/federatedIdentityCredentials" --body @body.json

cat <<EOF > body.json
{
    "name": "serverless-webapp-kotlin-demo-env-fd",
    "issuer": "https://token.actions.githubusercontent.com",
    "subject": "repo:Azure-Samples/serverless-webapp-kotlin:environment:Demo",
    "description": "GitHub account federated identity for Demo Environment",
    "audiences": [
        "api://AzureADTokenExchange"
    ]
}
EOF

az rest --method POST --uri "https://graph.microsoft.com/beta/applications/$objectId/federatedIdentityCredentials" --body @body.json

az role assignment create --assignee $appId --role contributor --scope /subscriptions/$SUBSCRIPTION_ID
az role assignment create --assignee $appId --role 'User Access Administrator' --scope /subscriptions/$SUBSCRIPTION_ID

  2. Configure secrets details in GitHub repo as described here Create GitHub secrets. Use below values mapped to relevant secrets in GitHub. Use Github Environmentto store these values.

    # AZURE_SUBSCRIPTION_ID
echo $SUBSCRIPTION_ID 
# AZURE_TENANT_ID   
echo $AZURE_TENANT    
# AZURE_CLIENT_ID      
echo $appId

  3. Configure variables to be used by different actions with same names as mentioned below. If followed steps for setting up applications locally, these variables should already be present in local terminal. If not, fetch it from azure environment. Store these values in the same github environment created in previous step.

    # If using custom domain, name of the apex domain.
echo $DNS_ZONE
# Azure region where the resources are deployed.
echo $AZURE_REGION
# Resource group where resources are deployed
echo $RESOURCE_GROUP

  4. Create a variable at repository level with name DEFAULT_ENVIRONMENT and its value as environment created above. This helps to quickly deploy the setup to another subscription/tenant/resource group quickly. Just create a new environment with required details workflow should target and point DEFAULT_ENVIRONMENT at repo level to that environment.

  5. Make sure to execute these flows in order on initial setup. Below are different workflows:

    1. Core infrastructure. If using custom domain, make sure to update the DNS registrar with name server info of azure dns zone that will be create via this workflow.
    2. Frontend infrastructure
    3. Backend infrastructure
    4. Deploy backend application i.e. azure function app
    5. Prepare DNS zone records for APIM Managed Cert. This workflow is manually dispatched beacuse the managed cert on API is still in preview and some steps for setup needs to be done from console before this workflow can run.
    6. Deploy frontend application. Make sure to update frontend app with backend api details in GlobalConstants

Run applications locally

If you want to test azure functions locally, it's possible to do so. Functions are dependent on some cloud resources like CosmoDB, storage accounts etc. to function locally.

  1. Because functions are dependent on cloud resources, appropriate role assignments needs to be done for local logged inn cli user to the resources.

    LOCAL_USER_ID=$(az ad signed-in-user show -o tsv --query id)

az role assignment create --role 'Storage Queue Data Contributor' --assignee-object-id $LOCAL_USER_ID

az role assignment create --role 'Storage Blob Data Owner' --assignee-object-id $LOCAL_USER_ID 

az role assignment create --role 'Storage Account Contributor' --assignee-object-id $LOCAL_USER_ID

KV_NAME=$(az deployment group show --name app-backend --output tsv --query 'properties.outputs.kvName.value')

DB_ACC_NAME=$(az deployment group show --name app-backend --output tsv --query 'properties.outputs.dbAccountName.value')

az keyvault set-policy --secret-permissions all --name $KV_NAME --object-id $LOCAL_USER_ID

CUSTOM_ROLE_ID=$(az cosmosdb sql role definition list -a $DB_ACC_NAME -o tsv --query "[?typePropertiesType == 'CustomRole']|[0].id")

az cosmosdb sql role assignment create -p $LOCAL_USER_ID -d $CUSTOM_ROLE_ID -a $DB_ACC_NAME -s $DB_ACC_NAME

  2. Fetch the function app settings locally.

    cd backend/faceApp

func azure functionapp fetch-app-settings $FN_APP_NAME --output-file local.settings.json

mvn clean install -DappName=$FN_APP_NAME

mvn azure-functions:run -DresourceGroup=$RESOURCE_GROUP -DappName=$FN_APP_NAME

  3. Setup ngrok to create event subscription for when any image is created in the image storage blob container it triggers function locally to process that image.

    Follow this Run ngrok guide. Copy the HTTPS URL generated when ngrok is run. This value is used to determine the webhook endpoint on your computer exposed using ngrok.

    IMAGE_STORAGE=$(az deployment group show --name app-backend --output tsv --query 'properties.outputs.imageStorageAccountName.value')

echo $IMAGE_STORAGE

az deployment group create -f backend/bicep/eventSubscription.bicep --name app-backend-event-subscription -p storageAccountName=$IMAGE_STORAGE functionApp='' devSubscriptionUrl=<<replace with ngrok generated https url>>

  4. If needed to test end to end using frontend application as well, get the frontend app up and running as well in a separate terminal window. Open GlobalConstants.ts and update properties UPLOAD_URL and FIND_IMAGE to localhost urls

    cd frontend
npm run start

Security

See CONTRIBUTING for more information.

License

This library is licensed under the MIT-0 License. See the LICENSE file.

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