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Kubernetes Restart Operator: periodically restart common Kubernetes resources using the `kubectl rollout restart` command.

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cron-restart

The Kubernetes Restart Operator is designed to periodically restart common Kubernetes resources using the kubectl rollout restart command. This operator supports Deployments, StatefulSets, DaemonSets, and other resources that can be restarted using this command.

Features

  • Scheduled Restarts: Automatically restart resources on a predefined schedule.
  • Resource Support: Works with any resource that supports kubectl rollout restart.
  • Custom Schedules: Define custom restart schedules using Cron syntax.
  • Flexible Time Configuration: Supports skipping specified dates and run once.

Prerequisites

  • go version v1.22.0+
  • docker version 17.03+.
  • kubectl version v1.11.3+.
  • Access to a Kubernetes v1.11.3+ cluster.
  • Helm 3 (for installation via Helm).

Installation

Using Helm

  1. Package the Helm Chart:

    helm package cron-restart

  2. Install the operator:

    helm install cronrestart cron-restart-0.1.0.tgz -n kube-system

Usage

Try out the examples in the examples folder.

  1. Deploy resources in deployment_cronrestart.yaml

    kubectl apply -f deployment_cronrestart.yaml

  2. Check the status of the deployment

    ➜  examples kubectl get deploy nginx-deployment-basic
NAME                     READY   UP-TO-DATE   AVAILABLE   AGE
nginx-deployment-basic   2/2     2            2           2m2s

  3. Check the restart event

    ➜  examples kubectl describe deploy nginx-deployment-basic
Name:                   nginx-deployment-basic
Namespace:              default
CreationTimestamp:      Mon, 03 Mar 2025 11:22:31 +0800
Labels:                 app=nginx
Annotations:            deployment.kubernetes.io/revision: 2
Selector:               app=nginx
Replicas:               2 desired | 2 updated | 2 total | 2 available | 0 unavailable
StrategyType:           RollingUpdate
MinReadySeconds:        0
RollingUpdateStrategy:  25% max unavailable, 25% max surge
Pod Template:
Labels:       app=nginx
Annotations:  kubectl.kubernetes.io/restartedAt: 2025-03-03T11:30:00+08:00
Containers:
   nginx:
   Image:         nginx:1.7.9
   Port:          80/TCP
   Host Port:     0/TCP
   Environment:   <none>
   Mounts:        <none>
Volumes:         <none>
Node-Selectors:  <none>
Tolerations:     <none>
Conditions:
Type           Status  Reason
----           ------  ------
Available      True    MinimumReplicasAvailable
Progressing    True    NewReplicaSetAvailable
OldReplicaSets:  nginx-deployment-basic-84df99548d (0/0 replicas created)
NewReplicaSet:   nginx-deployment-basic-58ddd489d (2/2 replicas created)
Events:
Type    Reason             Age    From                   Message
----    ------             ----   ----                   -------
Normal  ScalingReplicaSet  8m15s  deployment-controller  Scaled up replica set nginx-deployment-basic-84df99548d to 2
Normal  ScalingReplicaSet  46s    deployment-controller  Scaled up replica set nginx-deployment-basic-58ddd489d to 1
Normal  ScalingReplicaSet  45s    deployment-controller  Scaled down replica set nginx-deployment-basic-84df99548d to 1
Normal  ScalingReplicaSet  45s    deployment-controller  Scaled up replica set nginx-deployment-basic-58ddd489d to 2
Normal  ScalingReplicaSet  44s    deployment-controller  Scaled down replica set nginx-deployment-basic-84df99548d to 0

  4. Check controller's log

    ➜  examples kubectl logs -n kube-system kubernetes-cronrestarter-controller-86689855c9-mjplw
2025-03-03T11:08:43+08:00	INFO	setup	starting manager
2025-03-03T11:08:43+08:00	INFO	starting server	{"name": "health probe", "addr": "[::]:8081"}
2025-03-03T11:08:43+08:00	INFO	Starting EventSource	{"controller": "cronrestarter", "controllerGroup": "autorestart.uni.com", "controllerKind": "CronRestarter", "source": "kind source: *v1.CronRestarter"}
2025-03-03T11:08:43+08:00	INFO	Starting Controller	{"controller": "cronrestarter", "controllerGroup": "autorestart.uni.com", "controllerKind": "CronRestarter"}
2025-03-03T11:08:43+08:00	INFO	Starting workers	{"controller": "cronrestarter", "controllerGroup": "autorestart.uni.com", "controllerKind": "CronRestarter", "worker count": 1}
I0303 11:18:43.776888       1 cronmanager.go:98] GC loop started every 10m0s
I0303 11:22:31.342943       1 cronrestarter_controller.go:73] Start to handle cronRestarter cronrestart-sample in default namespace
I0303 11:22:31.345413       1 cronmanager.go:48] cronRestarter job restart of cronRestarter cronrestart-sample in default created, 1 active jobs exist
I0303 11:22:31.354147       1 cronrestarter_controller.go:73] Start to handle cronRestarter cronrestart-sample in default namespace
I0303 11:28:43.762628       1 cronmanager.go:98] GC loop started every 10m0s
I0303 11:30:00.047956       1 cronrestarter_controller.go:73] Start to handle cronRestarter cronrestart-sample in default namespace
2025-03-03T11:30:00+08:00	DEBUG	events	cron restarter job restart executed successfully. Deployment nginx-deployment-basic in namespace default has been restarted successfully. job: restart id: 451ff9ef-31e7-4e90-b605-03c5d7d5c511	{"type": "Normal", "object": {"kind":"CronRestarter","namespace":"default","name":"cronrestart-sample","uid":"ee4e061c-f9f7-4631-8178-d1e8b8859fd0","apiVersion":"autorestart.uni.com/v1","resourceVersion":"16572"}, "reason": "Succeed"}

  5. Describe the cronrestarter

    ➜  examples kubectl describe cronrestarters cronrestart-sample
Name:         cronrestart-sample
Namespace:    default
Labels:       <none>
Annotations:  <none>
API Version:  autorestart.uni.com/v1
Kind:         CronRestarter
Metadata:
Creation Timestamp:  2025-03-03T03:22:31Z
Generation:          1
Resource Version:    16572
UID:                 ee4e061c-f9f7-4631-8178-d1e8b8859fd0
Spec:
Jobs:
   Name:      restart
   Schedule:  0 */10 * * * *
Restart Target Ref:
   API Version:  apps/v1
   Kind:         Deployment
   Name:         nginx-deployment-basic
Status:
Conditions:
   Job Id:           451ff9ef-31e7-4e90-b605-03c5d7d5c511
   Last Probe Time:  2025-03-03T03:30:00Z
   Message:          cron restarter job restart executed successfully. Deployment nginx-deployment-basic in namespace default has been restarted successfully. job: restart id: 451ff9ef-31e7-4e90-b605-03c5d7d5c511
   Name:             restart
   Run Once:         false
   Schedule:         0 */10 * * * *
   State:            Succeed
Restart Target Ref:
   API Version:  apps/v1
   Kind:         Deployment
   Name:         nginx-deployment-basic
Events:
Type    Reason   Age    From           Message
----    ------   ----   ----           -------
Normal  Succeed  5m58s  CronRestarter  cron restarter job restart executed successfully. Deployment nginx-deployment-basic in namespace default has been restarted successfully. job: restart id: 451ff9ef-31e7-4e90-b605-03c5d7d5c511

The State of the cronrestart job indicates its execution status. When the State is Succeed, it means the last execution was successful. When the State is Submitted, it means the cronrestart job has been submitted to the cron engine and is waiting to be executed. When the State is Failed, it means the last execution failed.

Configuration

The following example demonstrates how to configure a CronRestarter.

apiVersion: autorestart.uni.com/v1
kind: CronRestarter
metadata:
  name: cronrestart-sample
spec:
  restartTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: nginx-deployment-basic
  excludeDates:
   # exclude November 10th
   - "* * * 10 11 *"
   # exclude every Friday 
   - "* * * * * 5"
  jobs:
    - name: "restart"
      runOnce: false
      schedule: "0 */10 * * * *"
    - name: "special-restart"
      runOnce: true
      schedule: "@date 2025-4-1 11:11:11"

restartTargetRef

The restartTargetRef field specifies the workload to restart. If the workload supports the kubectl rollout restart command (such as Deployment and StatefulSet), CronRestarter should work well. Additionally, CronRestarter supports multiple cronrestart jobs in a single spec.

excludeDates

The excludeDates field is an array of dates. The job will skip execution when the date matches. The minimum unit is a day. If you want to skip a specific date (e.g., November 10th), you can specify the excludeDates field as follows:

  excludeDates:
  - "* * * 10 11 *"

jobs

The Job spec for cronrestart requires three fields:

  • name name should be unique within a single cronrestart spec. You can distinguish different job execution statuses by their job names.
  • runOnce If runOnce is set to true, the job will run only once and exit after the first execution.
  • schedule The format of schedule is similar to that of crontab. The kubernetes-cronrestarter-controller uses an enhanced cron library in Go （go-cron） which supports more expressive rules.

cron expression

The cron expression format is described below:

Field name Mandatory? Allowed values Allowed special characters
Seconds Yes 0-59 * / , -
Minutes Yes 0-59 * / , -
Hours Yes 0-23 * / , -
Day of month Yes 1-31 * / , - ?
Month Yes 1-12 or JAN-DEC * / , -
Day of week Yes 0-6 or SUN-SAT * / , - ?

Special Characters

  • Asterisk ( * )

    • The asterisk indicates that the cron expression will match for all values of the field. For example, using an asterisk in the 5th field (month) means every month.

  • Slash ( / )

    • Slashes are used to describe increments of ranges. For example, 3-59/15 in the 1st field (minutes) means the 3rd minute of the hour and every 15 minutes thereafter. The form */... is equivalent to the form first-last/..., which means an increment over the largest possible range of the field. The form N/... means starting at N and using the increment until the end of that specific range. It does not wrap around.

  • Comma ( , )

    • Commas are used to separate items of a list. For example, using MON,WED,FRI in the 5th field (day of week) means Mondays, Wednesdays, and Fridays.

  • Hyphen ( - )

    • Hyphens are used to define ranges. For example, 9-17 means every hour between 9am and 5pm inclusive.

  • Question mark ( ? )

    • A question mark can be used instead of * to leave either day-of-month or day-of-week blank.

Predefined Schedules

You may use one of several predefined schedules in place of a cron expression:

Entry Description Equivalent To
@yearly (or @annually) Run once a year, midnight, Jan. 1st 0 0 1 1 *
@monthly Run once a month, midnight, first of month 0 0 1 * *
@weekly Run once a week, midnight between Sat/Sun 0 0 * * 0
@daily (or @midnight) Run once a day, midnight 0 0 * * *
@hourly Run once an hour, beginning of hour 0 * * * *

Intervals

You can also schedule a job to execute at fixed intervals, starting at the time it's added or when cron is run. This is supported by formatting the cron spec like this:

@every <duration>

where <duration> is a string accepted by time.ParseDuration (https://golang.org/pkg/time/#ParseDuration).

For example, @every 1h30m10s indicates a schedule that activates after 1 hour, 30 minutes, and 10 seconds, and then every interval after that.

Note: The interval does not take the job runtime into account. For example, if a job takes 3 minutes to run and is scheduled to run every 5 minutes, it will have only 2 minutes of idle time between each run.

For more scheduling options, please refer to the cron package documentation.

Specific Date (@date)

You can use a specific date to schedule a job for restarting workloads. This is useful for daily promotions, for example.

Entry Description Equivalent To
@date 2025-4-1 21:54:00 Run once when the date is reached 0 54 21 1 4 *

Contributing

Contributions are welcome! Please submit an issue or pull request to contribute to this project.

License

This project is licensed under the Apache License 2.0. See the LICENSE file for details.

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Kubernetes Restart Operator: periodically restart common Kubernetes resources using the `kubectl rollout restart` command.

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