Indexed Job

This KEP extends kubernetes with user-friendly support for running parallel jobs. Here, parallel means multiple pods per Job. Jobs can be: - Embarrassingly parallel, where the pods have no dependencies between each other. - Tightly coupled, where the Pods communicate among themselves to make progress kubernetes/kubernetes#99497 We propose the addition of completion indexes into the Pods of a *Job [with fixed completion count]* to support running embarrassingly parallel programs, with a focus on ease of use for workload partitioning. We call this new Job pattern an Indexed Job, because each Pod of the Job specializes to work on a particular index, as if the Pods where elements of an array. With the addition of a headless Service, Pods can address another Pod with a specific index with a DNS lookup, because the index is part of the hostname. [with fixed completion count]: https://kubernetes.io/docs/concepts/workloads/controllers/job/#parallel-jobs