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03 - Configuration (Flex Consumption)

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

Prerequisites

Tool Version Purpose
JDK 17+ Compile and run Java functions locally
Maven 3.6+ Build and package Java artifacts
Azure Functions Core Tools v4 Start local host and publish artifacts
Azure CLI 2.61+ Provision Azure resources and inspect app state

Flex Consumption plan basics

Flex Consumption (FC1) keeps serverless economics while adding VNet integration, configurable instance memory (512 MB to 4096 MB), and per-function scaling. Microsoft recommends it for many new apps.

What You'll Build

You will standardize Java runtime app settings for Flex Consumption, understand platform-managed vs user-managed settings, and verify effective configuration from Azure.

flowchart TD
    A[local.settings.json] --> B[App Settings in Azure]
    B --> C[Functions host]
    C --> D[Java 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": "java",
    "FUNCTIONS_EXTENSION_VERSION": "~4",
    "QueueStorage": "UseDevelopmentStorage=true",
    "EventHubConnection__fullyQualifiedNamespace": "placeholder.servicebus.windows.net"
  }
}

Step 2 - Configure app settings in Azure

az functionapp config appsettings set \
  --name "$APP_NAME" \
  --resource-group "$RG" \
  --settings \
    "APP_ENV=production" \
    "JAVA_OPTS=-Xmx512m"

FUNCTIONS_WORKER_RUNTIME is platform-managed

On Flex Consumption, FUNCTIONS_WORKER_RUNTIME is set by the platform during az functionapp create. You cannot override it via app settings. This differs from Consumption where you set it explicitly.

Step 3 - Set JVM and runtime guardrails

az functionapp config appsettings set \
  --name "$APP_NAME" \
  --resource-group "$RG" \
  --settings \
    "JAVA_OPTS=-Xmx512m -XX:+UseContainerSupport"

Step 4 - Validate pom.xml dependency and plugin

Ensure the Maven project includes the Azure Functions Java library:

<dependency>
    <groupId>com.microsoft.azure.functions</groupId>
    <artifactId>azure-functions-java-library</artifactId>
    <version>3.1.0</version>
</dependency>

And the Maven plugin for packaging:

<plugin>
    <groupId>com.microsoft.azure</groupId>
    <artifactId>azure-functions-maven-plugin</artifactId>
    <version>1.34.0</version>
    <configuration>
        <appName>${functionAppName}</appName>
        <resourceGroup>${functionResourceGroup}</resourceGroup>
        <runtime>
            <os>linux</os>
            <javaVersion>17</javaVersion>
        </runtime>
    </configuration>
</plugin>

Step 5 - Verify effective settings

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

Step 6 - Verify runtime behavior with info endpoint

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

{
  "name": "azure-functions-java-guide",
  "version": "1.0.0",
  "java": "17.0.14",
  "os": "Linux",
  "environment": "production",
  "functionApp": "func-jflex-04100144"
}

Verification

App settings output (showing key fields):

Name                                    Value
--------------------------------------  -----------------------------------------------
AzureWebJobsStorage                     DefaultEndpointsProtocol=https;AccountName=...
APPLICATIONINSIGHTS_CONNECTION_STRING   InstrumentationKey=<instrumentation-key>;...
APP_ENV                                 production
JAVA_OPTS                               -Xmx512m -XX:+UseContainerSupport
QueueStorage                            DefaultEndpointsProtocol=https;AccountName=...
EventHubConnection                      Endpoint=sb://placeholder.servicebus.windows.net/;...

Platform-managed settings

On Flex Consumption, FUNCTIONS_WORKER_RUNTIME and FUNCTIONS_EXTENSION_VERSION may not appear in the app settings list because they are managed by the platform.

Next Steps

Next: 04 - Logging and Monitoring

See Also

Sources