[SPARK-49714] Add Java 21-based SparkPi example

[dongjoon-hyun]

What changes were proposed in this pull request?

This PR aims to add Java 21-based SparkPi example.

Why are the changes needed?

Apache Spark starts to publish Java 21-based image from Today (2024-09-19). This new example will illustrate how to use it.

• [SPARK-49703] Publish Java 21 Docker image for preview1 spark-docker#69

Does this PR introduce any user-facing change?

No, this is a new example.

How was this patch tested?

Manual review.

$ kubectl apply -f examples/pi-java21.yaml 

$ kubectl get sparkapp NAME CURRENT STATE AGE pi-java21 ResourceReleased 28s 

$ kubectl describe sparkapp pi-java21 Name: pi-java21 Namespace: default Labels: <none> Annotations: <none> API Version: spark.apache.org/v1alpha1 Kind: SparkApplication Metadata: Creation Timestamp: 2024-09-19T04:08:16Z Finalizers: sparkapplications.spark.apache.org/finalizer Generation: 2 Resource Version: 95294 UID: 2bc46e8d-6339-4867-9a28-6552c6c471e5 Spec: Application Tolerations: Application Timeout Config: Driver Ready Timeout Millis: 300000 Driver Start Timeout Millis: 300000 Executor Start Timeout Millis: 300000 Force Termination Grace Period Millis: 300000 Termination Requeue Period Millis: 2000 Instance Config: Init Executors: 0 Max Executors: 0 Min Executors: 0 Resource Retain Policy: OnFailure Restart Config: Max Restart Attempts: 3 Restart Backoff Millis: 30000 Restart Policy: Never Deployment Mode: ClusterMode Driver Args: Jars: local:///opt/spark/examples/jars/spark-examples.jar Main Class: org.apache.spark.examples.SparkPi Runtime Versions: Scala Version: 2.13 Spark Version: 4.0.0-preview1 Spark Conf: spark.dynamicAllocation.enabled: true spark.dynamicAllocation.maxExecutors: 3 spark.dynamicAllocation.shuffleTracking.enabled: true spark.kubernetes.authenticate.driver.serviceAccountName: spark spark.kubernetes.container.image: apache/spark:4.0.0-preview1-java21-scala spark.log.structuredLogging.enabled: false Status: Current Attempt Summary: Attempt Info: Id: 0 Current State: Current State Summary: ResourceReleased Last Transition Time: 2024-09-19T04:08:33.316041381Z State Transition History: 0: Current State Summary: Submitted Last Transition Time: 2024-09-19T04:08:16.584629470Z Message: Spark application has been created on Kubernetes Cluster. 1: Current State Summary: DriverRequested Last Transition Time: 2024-09-19T04:08:17.269457304Z Message: Requested driver from resource scheduler. 2: Current State Summary: DriverStarted Last Transition Time: 2024-09-19T04:08:17.809898304Z Message: Driver has started running. 3: Current State Summary: DriverReady Last Transition Time: 2024-09-19T04:08:17.810393971Z Message: Driver has reached ready state. 4: Current State Summary: RunningHealthy Last Transition Time: 2024-09-19T04:08:17.828526471Z Message: Application is running healthy. 5: Current State Summary: Succeeded Last Transition Time: 2024-09-19T04:08:33.241514089Z Message: Spark application completed successfully. 6: Current State Summary: ResourceReleased Last Transition Time: 2024-09-19T04:08:33.316041381Z Events: <none> 

Was this patch authored or co-authored using generative AI tooling?

No.

[dongjoon-hyun]

cc @viirya

[dongjoon-hyun]

Thank you! Merged to main.