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Winter Soldier

Winter Soldier can be used to

  • cleans up (delete) Kubernetes resources
  • reduce workload pods to 0

at user defined time of the day and conditions. Winter Soldier is an operator which expects conditions to be defined using CRD hibernator.

Motivation

Overtime Kubernetes clusters end up with workloads which have outlived their utility and add to the TCO of infrastructure. Some prominent use cases are

  1. Microservices in QA environment are not required during off-work hours or during weekends
  2. UAT environment is required only before releasing to production but is kept running because of time required to bring it up
  3. Workload created for POC purpose, eg - Kafka, Mongodb, SQL workload, are left running long after POC is done

Configuration

Actions

Winter Soldier supports two type of actions on the workload

Delete

This action can be used to delete any Kubernetes object. eg

spec:
 action: delete

Sleep

This condition can be used to change replicas of workload to 0. eg

spec:
  action: sleep

At the end of hibernation cycle it sets replica count of workload to same number as it was before hibernation.

Conditions

Hibernator uses gjson to select fields in Kubernetes objects and expr for conditions. Please check them out for advanced cases.

Objects can be included and excluded based on

  1. Label Selector
  2. Object Kind
  3. Name
  4. Namespace
  5. Any field in the kubernetes object
selectors:
- inclusions:
  - objectSelector:
      name: ""
      type: "deployment"
      fieldSelector:
      - AfterTime(Now(), AddTime(ParseTime({{metadata.creationTimestamp}}, '2006-01-02T15:04:05Z'), '10h'))
    namespaceSelector:
      name: "all"
  exclusions: 
  - objectSelector:
      name: ""
      type: "deployment"
    namespaceSelector:
      name: "kube-system"

The above example will select Deployment kind objects which have been created 10 hours ago across all namespaces excluding kube-system namespace. Winter soldier exposes following functions to handle time, cpu and memory.

  1. ParseTime - This function can be used to parse time. For eg to parse creationTimestamp use ParseTime({{metadata.creationTimestamp}}, '2006-01-02T15:04:05Z')
  2. AddTime - This can be used to add time. For eg AddTime(ParseTime({{metadata.creationTimestamp}}, '2006-01-02T15:04:05Z'), '-10h') ll add 10h to the time. Use d for day, h for hour, m for minutes and s for seconds. Use negative number to get earlier time.
  3. Now - This can be used to get current time.
  4. CpuToNumber - This can be used to compare CPU. For eg any({{spec.containers.#.resources.requests}}, { MemoryToNumber(.memory) < MemoryToNumber('60Mi')}) will check if any resource.requests is less than 60Mi

Time Range

This defines the execution time

spec:
  action: sleep
  timeRangesWithZone:
    reSyncInterval: 300 # in minutes
    timeZone: "Asia/Kolkata"
    timeRanges:
      - timeFrom: 00:00
        timeTo: 23:59:59
        weekdayFrom: Sat
        weekdayTo: Sun
      - timeFrom: 00:00
        timeTo: 08:00
        weekdayFrom: Mon
        weekdayTo: Fri
      - timeFrom: 20:00
        timeTo: 23:59:59
        weekdayFrom: Mon
        weekdayTo: Fri

Above settings will take action on Sat and Sun from 00:00 to 23:59:59, and on Mon-Fri from 00:00 to 08:00 and 20:00 to 23:59:59. If action:sleep then runs hibernate at timeFrom and unhibernate at timeTo. If action: delete then it will delete workloads at timeFrom and timeTo.

Other Configurations

  1. Pause - To pause execution
spec:
  pause: true
  1. PauseUntil - To pause execution
spec:
  pauseUntil: "Jan 2, 2026 3:04pm"
  1. Hibernate - Hibernates immediately till this flag is unset
spec:
  hibernate: true
  1. UnHiberbate - UnHibernates immediately till this flag is unset
spec:
  unhibernate: true

** Please Note: If both hibernate and unHibernate flag are set then hibernate flag is ignored