Add blog post for job tracking with finalizers GA

content/en/blog/_posts/2022-12-01-scalable-job-tracking-ga/index.md

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+---
+layout: blog
+title: "Scalable Job tracking goes GA to support massively parallel batch workloads"
+date: 2022-12-01
+slug: "scalable-job-tracking-ga"
+---
+
+**Authors:** Aldo Culquicondor (Google)
+
+The Kubernetes 1.26 release includes a stable implementation of the Job
+controller that can reliably track a large amount of Jobs with high levels of
+parallelism. SIG Apps have worked on this foundational improvement, under
+the feature gate `JobTrackingWithFinalizers`, since Kubernetes 1.22. After
+multiple iterations and scale verifications, this is now the default
+implementation of the Job controller.
+
+Paired with the Indexed [completion mode](/docs/concepts/workloads/controllers/job/#completion-mode),
+the Job controller can handle massively parallel batch Jobs, supporting up to
+100 thousand concurrent Pods.
+
+The new implementation also enables better control over failures and retries,
+such as [Pod failure policy](/docs/concepts/workloads/controllers/job/#pod-failure-policy)
+
+## The problem with the legacy implementation
+
+Generally, Kubernetes workload controllers, such as ReplicaSet or StatefulSet
+rely on the existence of Pods or other objects in the API to determine the
+status of the Workload and whether replacements are needed.
+For example, if a Pod that belonged to a ReplicaSet terminates or ceases to
+exist, the ReplicaSet controller needs to create a replacement Pod to satisfy
+the `.spec.replicas` field.
+
+Since its inception, the Job controller also relied on the existence on Pods
+to track Job status. However, a Job has [completion](/docs/concepts/workloads/controllers/job/#completion-mode)
+and [failure handling](/docs/concepts/workloads/controllers/job/#handling-pod-and-container-failures)
+policies. The Job controller needs to know under which circumstances a Pod
+finished to determine whether to create a replacement Pod or mark the Job as
+completed or failed. As a result, the Job
+controller depended on Pods, even terminated ones, to remain in the API in order
+to keep track of the status.
+
+This dependency made the tracking of Job status unreliable, because Pods can be
+deleted from the API for a number of reasons, including:
+- The garbage collector removing orphan Pods when a Node goes down.
+- The garbage collector removing terminated Pods when they reach a treshhold.
+- The Kubernetes scheduler preempting a Pod to accomodate higher priority Pods.
+- The taint manager evicting a Pod that doesn't tolerate a `NoExecute` taint.
+- External controllers, not included as part of Kubernetes, or humans deleting
+  Pods.
+
+## How did we solve the problem?
+
+
+
+## How do I use this feature?
+
+
+
+## Deprecation notices
+
+In Kubernetes 1.21, we [introduced Indexed Jobs](/blog/2021/04/19/introducing-indexed-jobs/)
+as a simple way of setting up parallel Jobs.