feat(batch): array jobs — real child containers + parent aggregation (batch 3)

[vieiralucas]

Summary

AWS Batch batch 3 — array jobs (the highest-demand Batch feature after real execution).

• SubmitJob with arrayProperties.size = N spawns N child jobs <parent>:<index>, each a real container with AWS_BATCH_JOB_ARRAY_INDEX injected so it selects its slice of work, launched on the ECS engine via the batch-2 path.
• The array parent's status + arrayProperties.statusSummary aggregate the children live at DescribeJobs time — SUCCEEDED only when every child exits 0, FAILED if any child failed once all are terminal, else RUNNING/PENDING.
• Refactored the ECS-launch-or-park logic into a shared launch_job (single + array submits).

Test plan

• Unit (13): array spawn + parent aggregation, status-summary terminal logic, AWS_BATCH_JOB_ARRAY_INDEX injection, plus existing control-plane/resource-mapping.
• Docker-gated e2e: array_job_runs_every_child_and_parent_succeeds — array size 3 runs three real alpine containers → parent SUCCEEDED, statusSummary.SUCCEEDED == 3. Passes locally.
• cargo clippy -p fakecloud-batch -p fakecloud-e2e --all-targets -- -D warnings clean. Docs updated.

Next

Job dependencies (dependsOn), retry strategies + timeouts, then a CloudFormation AWS::Batch::* provisioner + tfacc.

---

Summary by cubic

Add AWS Batch array jobs: SubmitJob with arrayProperties.size spawns real child containers and the parent aggregates live status. Also refactors the ECS launch flow into a shared launch_job used by single and array submits.

• New Features

  • SubmitJob with arrayProperties.size=N spawns N real child jobs <parent>:<index>, each with AWS_BATCH_JOB_ARRAY_INDEX.
  • Parent aggregates at DescribeJobs: SUCCEEDED only if all children exit 0; FAILED if any failed once all are terminal; otherwise RUNNING/PENDING.

• Refactors

  • Extracted ECS launch/park logic into launch_job, shared by single and array submits.

^{Written for commit 8ffa257. Summary will update on new commits.}