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☑️ Ensure Rollout has revision history set

A Rollout's revision history is stored in the ReplicaSets it controls.

.spec.revisionHistoryLimit is an optional field that specifies the number of old ReplicaSets to retain to allow rollback. These old ReplicaSets consume resources in etcd and crowd the output of kubectl get rs. The configuration of each Deployment revision is stored in its ReplicaSets; therefore, once an old ReplicaSet is deleted, you lose the ability to rollback to that revision of Deployment. By default, 10 old ReplicaSets will be kept, however, its ideal value depends on the frequency and stability of new Deployments.

More specifically, setting this field to zero means that all old ReplicaSets with 0 replicas will be cleaned up. In this case, a new Deployment rollout cannot be undone, since its revision history is cleaned up.

Targeted objects by this rule (types of kind): Rollout

Complexity: medium (What does this mean?)


This rule will fail

If the revisionHistoryLimit key is not set, or set to a value of 0:

kind: Rollout
  revisionHistoryLimit: 0
kind: Rollout
  replicas: 5

Rule output in the CLI

$ datree test *.yaml

>> File: failExample.yaml
❌ Ensure Rollout has revision history set [1 occurrence]
💡 Incorrect value for key `revisionHistoryLimit` - value above 0 is required to enable rolling back from a failed deployment

How to fix this failure

Set the revisionHistoryLimit key with a non-zero value:

kind: Rollout
  revisionHistoryLimit: 3

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