AWS Batch array jobs now support array size environment variable

AWS Batch now exposes array size as a container environment variable of an array child job. With this feature, customers can use array size in the logic of their applications (e.g. to divide data between jobs for parallel processing). AWS Batch customers can now access array size via AWS\_BATCH\_JOB\_ARRAY\_SIZE environment variable. Visit [job environment variables](https://docs.aws.amazon.com/batch/latest/userguide/job%5Fenv%5Fvars.html) page of AWS Batch user guide for more details. Array size environment variable is now supported in all [AWS Regions](https://aws.amazon.com/about-aws/global-infrastructure/regional-product-services/) where AWS Batch is currently available. To learn more about AWS Batch, see the [AWS Batch User Guide](https://docs.aws.amazon.com/batch/latest/userguide/what-is-batch.html).