cloudwatch: Arn.split cannot parse AWS Batch Job queue ARN

[kcrimson]

Describe the bug

I am trying to create a CloudWatch Alarm for AWS Batch queues. CDK synth produces the following CloudFormation template:

BatchWatchdogBatchWatchdogAlertsworkerm6gdlargeAlarm7BA82391:
    Type: AWS::CloudWatch::Alarm
    Properties:
      ActionsEnabled: false
      ComparisonOperator: GreaterThanOrEqualToThreshold
      DatapointsToAlarm: 3
      Dimensions:
        - Name: BatchJobQueue
          Value:
            Fn::Select:
              - 2
              - Fn::Split:
                  - /
                  - Fn::Select:
                      - 5
                      - Fn::Split:
                          - ":"
                          - Fn::Select:
                              - 1
                              - Fn::Split:
                                  - /
                                  - Fn::Select:
                                      - 5
                                      - Fn::Split:
                                          - ":"
                                          - Fn::GetAtt:
                                              - workerm6gdlargeJobQueue4AFBF4B1
                                              - JobQueueArn
      EvaluationPeriods: 5
      MetricName: TimeInQueue
      Namespace: benchmarking
      Period: 300
      Statistic: Average
      Tags:
        - Key: owner
          Value: benchmark
        - Key: project
          Value: benchmarking-batch-infrastructure
        - Key: stage
          Value: staging
      Threshold: 3600
      Unit: Seconds

Expected Behavior

What is expected is to set the value of the Alarm dimension to the AWS batch job queue name.

When I run this code as a code snippet, it extracts the resource name properly, but it generates an invalid CF template

|  Welcome to JShell -- Version 11.0.8
|  For an introduction type: /help intro

jshell> import software.amazon.awscdk.Arn;

jshell> import software.amazon.awscdk.ArnFormat

jshell> Arn.split("arn:aws:batch:us-east-1:111122223333:job-queue/JobQueueName",ArnFormat.SLASH_RESOURCE_SLASH_RESOURCE_NAME).getResourceName();
$3 ==> "JobQueueName"

Current Behavior

When I deploy this stack, I get the following error:

Failed resources:
benchmarking-batch-infrastructure-staging-eu-central-1 | 4:11:00 PM | CREATE_FAILED        | AWS::CloudWatch::Alarm         | BatchWatchdog/BatchWatchdogAlerts/worker-m6gd.large-Alarm (BatchWatchdogBatchWatchdogAlertsworkerm6gdlargeAlarm7BA82391) Template error: Fn::Select  cannot select nonexistent value at index 5

Reproduction Steps

The Java code which creates CloudWatch alarms, looks like this:

private void createAlarm(BatchJobQueue batchJobQueue) {
        var resourceName = Arn.split(batchJobQueue.getJobQueueName(), ArnFormat.SLASH_RESOURCE_SLASH_RESOURCE_NAME)
                .getResourceName();
        Alarm.Builder.create(this, batchJobQueue.getNode().getId() + "-Alarm")
                .actionsEnabled(false)
                .metric(Metric.Builder.create()
                        .namespace(BatchWatchDog.BENCHMARKING_METRIC_NAMESPACE)
                        .metricName(BatchWatchDog.TIME_IN_QUEUE_METRIC_NAME)
                        .dimensionsMap(Map.of(BatchWatchDog.BATCH_JOB_QUEUE_DIMENSION, resourceName))
                        .period(software.amazon.awscdk.Duration.minutes(5))
                        .unit(Unit.SECONDS)
                        .statistic(Stats.AVERAGE)
                        .build())
                .evaluationPeriods(5)
                .datapointsToAlarm(3)
                .threshold(Duration.ofHours(1).toSeconds())
                .comparisonOperator(ComparisonOperator.GREATER_THAN_OR_EQUAL_TO_THRESHOLD)
                .build();
    }

### Possible Solution

_No response_

### Additional Information/Context

_No response_

### CDK CLI Version

2.149.0

### Framework Version

_No response_

### Node.js Version

v20.15.1

### OS

Ubuntu  24.04 LTS

### Language

Java

### Language Version

Java 11

### Other information

_No response_

[pahud]

Looks like you are trying to createAlarm from your Java code with a BatchJobQueue and you need to find out the resourceName of that BatchJobQueue. And you are trying to Arn.split batchJobQueue.getJobQueueName() to get the resourceName.

My questions:

1. It's not clear what batchJobQueue.getJobQueueName() would return, I can't find this method in the CDK source. Is this your private function? Does it return a full ARN or just the job queue name? Arn.split() essentially splits the ARN, it can't handle the resource name.
2. Before you create the Alarm, are you able to CfnOutput the resourceName variable and make sure it is exactly what you need?

[github-actions]

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