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03 - Configuration (Dedicated)

Apply environment settings, runtime configuration, and host-level options so the same artifact can run across environments.

Prerequisites

Tool Version Purpose
.NET SDK 8.0 (LTS) Build and run isolated worker functions
Azure Functions Core Tools v4 Start local host and publish artifacts
Azure CLI 2.61+ Provision Azure resources and inspect app state

Dedicated plan basics

Dedicated (App Service Plan) runs on pre-provisioned compute with predictable cost. Always On keeps the host loaded for non-HTTP triggers. Supports VNet integration and deployment slots on eligible SKUs. No execution timeout limit.

What You'll Build

You will standardize .NET isolated worker app settings for Dedicated, keep environment-specific values outside the artifact, and verify effective configuration from Azure.

flowchart TD
    A[local.settings.json] --> B[App Settings in Azure]
    B --> C[Functions host]
    C --> D[dotnet-isolated worker startup]
    D --> E[Function method behavior]

Steps

Step 1 - Baseline local settings

The reference app includes a local.settings.json.example template:

{
  "IsEncrypted": false,
  "Values": {
    "AzureWebJobsStorage": "UseDevelopmentStorage=true",
    "FUNCTIONS_WORKER_RUNTIME": "dotnet-isolated",
    "QueueStorage": "UseDevelopmentStorage=true",
    "EventHubConnection": "Endpoint=sb://placeholder.servicebus.windows.net/;SharedAccessKeyName=placeholder;SharedAccessKey=cGxhY2Vob2xkZXI=;EntityPath=events"
  }
}

Local vs Azure settings

local.settings.json is used only for local development. In Azure, app settings are stored as environment variables in the Function App configuration.

Step 2 - Configure app settings in Azure

az functionapp config appsettings set \
  --name "$APP_NAME" \
  --resource-group "$RG" \
  --settings \
    "APP_ENV=production" \
    "AZURE_FUNCTIONS_ENVIRONMENT=Production"

Step 3 - Set runtime guardrails

az functionapp config appsettings set \
  --name "$APP_NAME" \
  --resource-group "$RG" \
  --settings \
    "FUNCTIONS_EXTENSION_VERSION=~4" \
    "FUNCTIONS_WORKER_RUNTIME=dotnet-isolated"

Step 4 - Enable Always On for non-HTTP triggers

az functionapp config set \
  --name "$APP_NAME" \
  --resource-group "$RG" \
  --always-on true

Always On is critical for Dedicated

Without Always On, the app may unload after idle periods, causing timer and queue triggers to stop firing. Always On is available on Basic (B1) and higher SKUs.

Step 5 - Review Program.cs for isolated hosting

Ensure the host builder uses the ASP.NET Core integration model:

using Microsoft.Azure.Functions.Worker;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

var host = new HostBuilder()
    .ConfigureFunctionsWebApplication()
    .ConfigureServices(services =>
    {
        services.AddApplicationInsightsTelemetryWorkerService();
        services.ConfigureFunctionsApplicationInsights();
    })
    .Build();

host.Run();

Isolated worker model

The .NET isolated worker uses ConfigureFunctionsWebApplication() with ASP.NET Core integration. HTTP functions use HttpRequest and IActionResult from ASP.NET Core, and logging is constructor-injected with ILogger<T>.

Step 6 - Verify effective settings

az functionapp config appsettings list \
  --name "$APP_NAME" \
  --resource-group "$RG" \
  --output table

Step 7 - Verify runtime behavior with info endpoint

curl --request GET "https://$APP_NAME.azurewebsites.net/api/info"

The /api/info endpoint reads environment variables at runtime, confirming the deployed configuration:

{
  "name": "azure-functions-dotnet-guide",
  "version": "1.0.0",
  "dotnet": ".NET 8.0.23",
  "os": "Linux",
  "environment": "production",
  "functionApp": "func-dnetded-04100301"
}

Verification

App settings output (showing key fields):

Name                                      Value                                                SlotSetting
----------------------------------------  ---------------------------------------------------  -----------
FUNCTIONS_WORKER_RUNTIME                  dotnet-isolated                                      False
FUNCTIONS_EXTENSION_VERSION               ~4                                                   False
APP_ENV                                   production                                           False
AZURE_FUNCTIONS_ENVIRONMENT               Production                                           False
AzureWebJobsStorage                       DefaultEndpointsProtocol=https;AccountName=...       False
APPLICATIONINSIGHTS_CONNECTION_STRING     InstrumentationKey=<instrumentation-key>;...          False
QueueStorage                              DefaultEndpointsProtocol=https;AccountName=...       False
EventHubConnection                        Endpoint=sb://placeholder.servicebus.windows.net/;...False

Sensitive values in app settings

Connection strings and keys appear in the output. In production, use Azure Key Vault references instead of storing secrets directly in app settings.

Next Steps

Next: 04 - Logging and Monitoring

See Also

Sources