gbaeke/aca_scaling.md

## aca_scaling.md

      
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              aca_scaling.md
            
          
    Azure Container Apps: Bicep and scaling

Azure Service Bus

Create namespace and topic:
az group create --name rg-aca --location northeurope

namespaceName=MyNameSpace$RANDOM
az servicebus namespace create --resource-group rg-aca --name $namespaceName --location northeurope
az servicebus topic create --resource-group rg-aca --namespace-name $namespaceName --name mytopic
Get connection string:
az servicebus namespace authorization-rule keys list --resource-group rg-aca --namespace-name $namespaceName --name RootManageSharedAccessKey --query primaryConnectionString --output tsv
You will need the connection string when you deploy with Bicep.
Deploy with Bicep

Save the bicep file below as main.bicep:
param image string = 'ghcr.io/gbaeke/super:1.0.5'
@secure()
param sbconnstr string

resource la 'Microsoft.OperationalInsights/workspaces@2021-06-01' = {
  name: 'la-aca' 
  location: resourceGroup().location
  properties: {
    retentionInDays: 30
    sku: {
      name: 'PerGB2018'
    }
  }
}


resource env 'Microsoft.Web/kubeEnvironments@2021-02-01' = {
  name: 'myenv'
  location: resourceGroup().location
  properties: {
    // not recognized but type is required
    type: 'managed'
    internalLoadBalancerEnabled:false
    appLogsConfiguration: {
      destination: 'log-analytics'
      logAnalyticsConfiguration: {
        customerId: la.properties.customerId
        sharedKey: la.listKeys().primarySharedKey
      }
    }
    }
  }

  resource frontContainerApp 'Microsoft.Web/containerApps@2021-03-01' = {
    name: 'front'
    location: resourceGroup().location
    kind: 'containerapp'
    properties: {
      kubeEnvironmentId: env.id
      configuration: {
        ingress: {
          external: true
          targetPort: 8080
        }
      }
      template: {
        containers: [
          {
            image: image
            name: 'super'
            env: [
              {
                name: 'WELCOME'
                value: 'Welcome to Container Apps'
              }
            ]
          }
        ]
        scale: {
          minReplicas: 0
          maxReplicas: 10
          rules: [
            {
            name: 'http-rule'
            http: {
              metadata: {
                concurrentRequests: '100'
              }
            }
            }
          ]
        }
      }
    }
  }

  resource pubSubContainerApp 'Microsoft.Web/containerApps@2021-03-01' = {
    name: 'pubsub'
    location: resourceGroup().location
    kind: 'containerapp'
    properties: {
      kubeEnvironmentId: env.id
      configuration: {
        ingress: {
          external: true
          targetPort: 8080
        }
        secrets: [
          {
            name: 'sbconnstr'
            value: sbconnstr
          }
        ]
      }
      template: {
        containers: [
          {
            image: image
            name: 'super'
            env: [
              {
                name: 'WELCOME'
                value: 'Welcome to Container Apps'
              }
            ]
          }
        ]
        scale: {
          minReplicas: 0
          maxReplicas: 10
          rules: [
            {
              name: 'topic-based-autoscaling'
              custom: {
                type: 'azure-servicebus'
                metadata: {
                  topicName: 'mytopic'
                  subscriptionName: 'pubsub'
                  messageCount: '2'
                }
                auth: [
                  {
                    secretRef: 'sbconnstr'
                    triggerParameter: 'connection'
                  }
                ]
              }

            }
          ]
        }
        dapr: {
          enabled: true
          appPort: 8080
          appId: 'pubsub'
          components: [
            {
              name: 'pubsub'
              type: 'pubsub.azure.servicebus'
              version: 'v1'
              metadata: [
                {
                  name: 'connectionString'
                  secretRef: 'sbconnstr'
                }
              ]
            }
          ]
        }
      }
    }
  }

To deploy the above to a resource group rg-aca, run:
az group create -n rg-aca -l northeurope

az deployment group create -n aca-deploy \
  -g rg-aca \
  --template-file ./main.bicep \
  -p sbconnstr='SB_CONNECTION_STRING'
Publish messages

Create a components folder and in that folder, create a file sd.yaml with the following content:
apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: sb
spec:
  type: pubsub.azure.servicebus
  version: v1
  metadata:
  - name: connectionString
    value: 'SERVICEBUS_CONNECTION_STRING'
On your computer with Dapr installed, use dapr run with the component in the components folder. Run the command from the folder that contains the components folder:
dapr run --dapr-http-port 3500 --app-id pubsubapp -d ./components

With the app running, run the following command to publish messages. The data you send with --data will be wrapped in a CloudEvents envelope.
while true; do dapr publish --publish-app-id pubsubapp --pubsub sb --topic mytopic --data '{"name":"geertje"}'; sleep 0.1; done

This publishes a message to the topic every tenth of a second. Adjust the timing with sleep as you see fit.
Revisions

To see the revisions of pubsub: az containerapp revision list -n pubsub -g rg-aca -o table
To get information about a revision: az containerapp revision show --app pubsub -n YOUR_REVISION -g rg-aca
Check the replicas: az containerapp revision show --app pubsub -n YOUR_REVISION -g rg-aca | jq .replicas
⚠️ Above command requires jq to be installed.
The number of revisions should be 10 if you are sending messages. If 0, start publishing again and start a watch on the replicas:
watch 'az containerapp revision show --app pubsub -n YOUR_REVISION -g rg-aca | jq .replicas'

When you stop publishing, the container app should be scaled to 0.