Environment Variables¶

Quick reference for Java Azure Functions operational workflows.

Topic/Command Groups¶

flowchart TD
    A[local.settings.json] --> B[App Settings]
    B --> C[Java worker startup]
    C --> D[Function behavior]

Variable	Purpose	Example
`FUNCTIONS_WORKER_RUNTIME`	Language worker selection	`java`
`FUNCTIONS_EXTENSION_VERSION`	Functions runtime version	`~4`
`AzureWebJobsStorage`	Trigger/binding storage	`UseDevelopmentStorage=true`
`APPLICATIONINSIGHTS_CONNECTION_STRING`	Telemetry destination	`InstrumentationKey=...`

Variable	Purpose	Example	Notes
`JAVA_HOME`	Java runtime location	Managed by platform	Do not override on Azure
`JAVA_OPTS`	JVM startup options	`-Xmx512m -XX:+UseG1GC`	Heap size, GC, and diagnostic flags
`FUNCTIONS_WORKER_JAVA_LOAD_APP_LIBS`	Load app libraries before worker libs	`true`	Useful for dependency conflict resolution
`WEBSITE_RUN_FROM_PACKAGE`	Run from immutable package	`1`	Recommended for production deployments

Common JAVA_OPTS configurations for Azure Functions:

Configuration	Value	Use case
Increase heap size	`-Xmx512m`	Memory-intensive processing
Use G1 GC	`-XX:+UseG1GC`	Balanced throughput and latency
Enable GC logging	`-Xlog:gc*`	Debug memory pressure (Java 11+)
Set timezone	`-Duser.timezone=UTC`	Consistent timestamp behavior

az functionapp config appsettings set --name $APP_NAME --resource-group $RG --settings "FUNCTIONS_WORKER_RUNTIME=java" "JAVA_OPTS=-Xmx512m"

CLI element	Explanation
Command(s)	`az functionapp config appsettings set`
Key flags	`--name`, `--resource-group`, `--settings`
Variables	`$APP_NAME`, `$RG`
Expected result	Azure CLI applies the configuration change; confirm the returned JSON or follow-up query shows the expected value.