Package com.microsoft.azure.functions.annotation

Annotation Type WarmupTrigger

@Retention(RUNTIME)
@Target(PARAMETER)
public @interface WarmupTrigger

The warmup trigger lets you define a function that's run when a new instance of your function app is started. You can use a warmup trigger to pre-load custom dependencies during the pre-warming process so your functions are ready to start processing requests immediately. Some actions for a warmup trigger might include opening connections, loading dependencies, or running any other custom logic before your app begins receiving traffic. The parameter type should be set as Object

The following example shows a Java function that logs the message body of the event hub trigger:

@FunctionName("Warmup")
 public void warmup(
    @WarmupTrigger Object warmupContext,
     final ExecutionContext context
 ) {
     context.getLogger().info("Function App instance is warm up");
 }

Since:

2.0.2

Optional Element Summary

Optional Elements

Modifier and Type	Optional Element	Description
java.lang.String	dataType	Defines how Functions runtime should treat the parameter value.
java.lang.String	name	The variable name used in function code for the request or request body.

Element Detail

name

java.lang.String name

The variable name used in function code for the request or request body.

Returns:

The variable name used in function code for the request or request body.

Default:

"warmupContext"

dataType

java.lang.String dataType

Defines how Functions runtime should treat the parameter value. Possible values are:

• "": get the value as a string, and try to deserialize to actual parameter type like POJO
• string: always get the value as a string
• binary: get the value as a binary data, and try to deserialize to actual parameter type byte[]

Returns:

The dataType which will be used by the Functions runtime.

Default:

""