Azure TimerTrigger Function

Important

For a general information about building and deploying Azure Functions with Spring Cloud Function, consult the Azure Adapter documentation.

Spring Cloud Function example for implementing Timer trigger for Azure Functions.

Running Locally

Note

To run locally on top of Azure Functions, and to deploy to your live Azure environment, you will need Azure Functions Core Tools installed along with the Azure CLI (see here) as well as the Use Azurite emulator for local Azure Storage development. For the emulator you can run a docker container (see below) or use the Visual-Studio-Code extension.

Here is how ot start the Azure emulator as docker container:

docker run --name azurite --rm -p 10000:10000 -p 10001:10001 -p 10002:10002 mcr.microsoft.com/azure-storage/azurite

Then build and run the sample:

./mvnw clean package
./mvnw azure-functions:run

The timer triggers the function every minute. In result the the uppercase Spring Cloud Function is called and uppercase the timeInfo and logs it into the context.

[2022-10-11T08:53:00.011Z] Execution Context Log - TimeInfo: {"Schedule":{"AdjustForDST":true},"ScheduleStatus":{"Last":"2022-10-11T10:52:00.003967+02:00","Next":"2022-10-11T10:53:00+02:00","LastUpdated":"2022-10-11T10:52:00.003967+02:00"},"IsPastDue":false}

The executeExpRetry handler demonstrates how to handle errors using the Retry policies. Sample emulates 3 errors on the first 3 executions and then continues as expected.

Running on Azure

Make sure you are logged in your Azure account.

az login

Build and deploy

./mvnw clean package
./mvnw azure-functions:deploy

Implementation details

The spring-cloud-function-adapter-azure dependency activates the AzureFunctionInstanceInjector:

<dependency>
	<groupId>org.springframework.cloud</groupId>
	<artifactId>spring-cloud-function-adapter-azure</artifactId>
</dependency>

(Version 4.x.x or higher)

The uppercase function with signature Function<Message<String>, Void> uppercase() is defined as @Bean in the TimeTriggerDemoApplication context.

	@Bean
	public Consumer<Message<String>> uppercase() {
		return message -> {
			String timeInfo = message.getPayload();
			String value = timeInfo.toUpperCase();

			logger.info("Timer is triggered with TimeInfo: " + value);

			// (Optionally) access and use the Azure function context.
			ExecutionContext context = (ExecutionContext) message.getHeaders().get(UppercaseHandler.EXECUTION_CONTEXT);
			context.getLogger().info("Execution Context Log - TimeInfo: " + value);

			// No response.
		};
	}

Tip	The uppercase function does not return value (e.g. Void output type) and is backed by java.util.Consumer.

The UppercaseHandler (marked as Spring @Component) implements the Azure function using the Azure Function Java API. Furthermore as Spring component the UppercaseHandler leverages the Spring configuration and programming model to inject the necessary services required by the functions.

@Component
public class UppercaseHandler {

    public static String EXECUTION_CONTEXT = "executionContext";

    @Autowired
    private Consumer<Message<String>> uppercase;

    @FunctionName("uppercase")
    public void execute(@TimerTrigger(name = "keepAliveTrigger", schedule = "0 */1 * * * *") String timerInfo,
            ExecutionContext context) {

        Message<String> message = MessageBuilder
                .withPayload(timerInfo)
                .setHeader(EXECUTION_CONTEXT, context)
                .build();

        this.uppercase.accept(message);
    }
}

Notes

• Change the spring-boot-maven-plugin to tiny in favor of the azure-functions-maven-plugin jar packaging.

• Add "AzureWebJobsStorage": "UseDevelopmentStorage=true" to the local.settings.json.