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03 - Configuration (Dedicated)

Manage environment settings, runtime options, and host behavior per environment.

Prerequisites

  • You completed 02 - First Deploy.
  • Your function app $APP_NAME is deployed and running on the Dedicated plan.

What You'll Build

  • Apply required app settings for the Node.js worker and runtime extension.
  • Tune host-level timeout behavior appropriate for Dedicated plan characteristics.
  • Validate effective settings in Azure.

Infrastructure Context

Plan: Dedicated (B1) | Timeout: Unlimited (-1) | Always On: ✅

Dedicated plans support unlimited function timeout (functionTimeout: -1), unlike Consumption (5/10 min) and Premium (30/60 min defaults). This makes Dedicated ideal for long-running workloads.

flowchart LR
    CLI[Azure CLI] -->|appsettings set| FA[Function App\nDedicated B1]

    subgraph CONFIG["App Settings"]
        RT["FUNCTIONS_WORKER_RUNTIME=node"]
        EXT["FUNCTIONS_EXTENSION_VERSION=~4"]
        MEM["node --max-old-space-size=4096"]
        TIMEOUT["functionTimeout: -1\n(unlimited)"]
    end

    FA --> CONFIG

    style FA fill:#ff8c00,color:#fff
    style CONFIG fill:#E3F2FD,stroke:#1976D2

Steps

  1. Configure app settings.

    az functionapp config appsettings set \
  --name "$APP_NAME" \
  --resource-group "$RG" \
  --settings \
    "FUNCTIONS_WORKER_RUNTIME=node" \
    "FUNCTIONS_EXTENSION_VERSION=~4" \
    "languageWorkers__node__arguments=--max-old-space-size=4096"

    Expected output (abridged):

    Name                                    SlotSetting    Value
--------------------------------------  -------------  -------------------------
FUNCTIONS_WORKER_RUNTIME                False          node
FUNCTIONS_EXTENSION_VERSION             False          ~4
languageWorkers__node__arguments        False          --max-old-space-size=4096

    FUNCTIONS_WORKER_RUNTIME on Dedicated

    On Dedicated plans, FUNCTIONS_WORKER_RUNTIME can be set via az functionapp config appsettings set without issues. On Flex Consumption, this setting is platform-managed and cannot be changed via CLI.

  2. Configure host timeout.

    The host.json file in your project root controls timeout behavior. For Dedicated plans, set functionTimeout to -1 for unlimited execution:

    {
  "version": "2.0",
  "functionTimeout": "-1"
}

    Timeout values by plan

    Plan Default Timeout Maximum
    Consumption 5 min 10 min
    Premium 30 min 60 min (unlimited with host.json)
    Dedicated 30 min Unlimited (-1)

  3. Validate effective config.

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

    Expected output (abridged):

    Name                                         Value
-------------------------------------------  -----------------------------------
FUNCTIONS_WORKER_RUNTIME                     node
FUNCTIONS_EXTENSION_VERSION                  ~4
AzureWebJobsStorage                          DefaultEndpointsProtocol=https;...
APPLICATIONINSIGHTS_CONNECTION_STRING        InstrumentationKey=...
EventHubConnection__fullyQualifiedNamespace  placeholder.servicebus.windows.net
QueueStorage                                 DefaultEndpointsProtocol=https;...
WEBSITE_RUN_FROM_PACKAGE                     1
languageWorkers__node__arguments             --max-old-space-size=4096

    WEBSITE_RUN_FROM_PACKAGE

    Dedicated plans automatically set WEBSITE_RUN_FROM_PACKAGE=1 for zip-based deployments. This setting is not required on Consumption or Flex Consumption.

  4. Review Dedicated-specific configuration notes.

    • Always On: Enable via portal or Bicep (alwaysOn: true) for non-HTTP triggers (timer, queue, blob). Without Always On, the app may idle and miss timer/queue events.
    • No content share: Unlike Premium and Consumption, Dedicated does not use WEBSITE_CONTENTAZUREFILECONNECTIONSTRING or WEBSITE_CONTENTSHARE.
    • Memory tuning: --max-old-space-size=4096 sets Node.js heap to 4 GB. Adjust based on your B1 (1.75 GB RAM) or S1/P1v3 tier.

Verification

The table confirms required Node.js worker settings are applied to the deployed app. Verify:

  • FUNCTIONS_WORKER_RUNTIME is node
  • FUNCTIONS_EXTENSION_VERSION is ~4
  • languageWorkers__node__arguments includes --max-old-space-size
  • WEBSITE_RUN_FROM_PACKAGE is 1

See Also

Sources