wuenping / kubernetes-cronhpa-controller

⏰kubernetes-cronhpa-controller is a HPA controller that allows to scale your workload based on time schedule.

kubernetes-cronhpa-controller

Overview

kubernetes-cronhpa-controller is a kubernetes cron horizontal pod autoscaler controller using crontab like scheme. You can use CronHorizontalPodAutoscaler with any kind object defined in kubernetes which support scale subresource(such as Deployment and StatefulSet).

Installation

1. install CRD

kubectl apply -f config/crds/autoscaling_v1beta1_cronhorizontalpodautoscaler.yaml

2. install RBAC settings

# create ClusterRole 
kubectl apply -f config/rbac/rbac_role.yaml

# create ClusterRolebinding and ServiceAccount 
kubectl apply -f config/rbac/rbac_role_binding.yaml

3. deploy kubernetes-cronhpa-controller

kubectl apply -f config/deploy/deploy.yaml

4. verify installation

kubectl get deploy kubernetes-cronhpa-controller -n kube-system -o wide 

➜  kubernetes-cronhpa-controller git:(master) ✗ kubectl get deploy kubernetes-cronhpa-controller -n kube-system
NAME                            DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
kubernetes-cronhpa-controller   1         1         1            1           49s

Example

Please try out the examples in the examples folder.

1. Deploy sample workload and cronhpa

kubectl apply -f examples/deployment_cronhpa.yaml 

2. Check deployment replicas

kubectl get deploy nginx-deployment-basic 

➜  kubernetes-cronhpa-controller git:(master) ✗ kubectl get deploy nginx-deployment-basic
NAME                     DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
nginx-deployment-basic   2         2         2            2           9s

3. Describe cronhpa status

kubectl describe cronhpa cronhpa-sample 

Name:         cronhpa-sample
Namespace:    default
Labels:       controller-tools.k8s.io=1.0
Annotations:  kubectl.kubernetes.io/last-applied-configuration:
                {"apiVersion":"autoscaling.alibabacloud.com/v1beta1","kind":"CronHorizontalPodAutoscaler","metadata":{"annotations":{},"labels":{"controll...
API Version:  autoscaling.alibabacloud.com/v1beta1
Kind:         CronHorizontalPodAutoscaler
Metadata:
  Creation Timestamp:  2019-04-14T10:42:38Z
  Generation:          1
  Resource Version:    4017247
  Self Link:           /apis/autoscaling.alibabacloud.com/v1beta1/namespaces/default/cronhorizontalpodautoscalers/cronhpa-sample
  UID:                 05e41c95-5ea2-11e9-8ce6-00163e12e274
Spec:
  Jobs:
    Name:         scale-down
    Schedule:     30 */1 * * * *
    Target Size:  1
    Name:         scale-up
    Schedule:     0 */1 * * * *
    Target Size:  3
  Scale Target Ref:
    API Version:  apps/v1beta2
    Kind:         Deployment
    Name:         nginx-deployment-basic
Status:
  Conditions:
    Job Id:           38e79271-9a42-4131-9acd-1f5bfab38802
    Last Probe Time:  2019-04-14T10:43:02Z
    Message:
    Name:             scale-down
    Schedule:         30 */1 * * * *
    State:            Submitted
    Job Id:           a7db95b6-396a-4753-91d5-23c2e73819ac
    Last Probe Time:  2019-04-14T10:43:02Z
    Message:
    Name:             scale-up
    Schedule:         0 */1 * * * *
    State:            Submitted
Events:               <none>

if the State of cronhpa job is Succeed that means the last execution is successful. Submitted means the cronhpa job is submitted to the cron engine but haven't be executed so far. Wait for 30s seconds and check the status.

➜  kubernetes-cronhpa-controller git:(master) kubectl describe cronhpa cronhpa-sample
Name:         cronhpa-sample
Namespace:    default
Labels:       controller-tools.k8s.io=1.0
Annotations:  kubectl.kubernetes.io/last-applied-configuration:
                {"apiVersion":"autoscaling.alibabacloud.com/v1beta1","kind":"CronHorizontalPodAutoscaler","metadata":{"annotations":{},"labels":{"controll...
API Version:  autoscaling.alibabacloud.com/v1beta1
Kind:         CronHorizontalPodAutoscaler
Metadata:
  Creation Timestamp:  2019-04-15T06:41:44Z
  Generation:          1
  Resource Version:    15673230
  Self Link:           /apis/autoscaling.alibabacloud.com/v1beta1/namespaces/default/cronhorizontalpodautoscalers/cronhpa-sample
  UID:                 88ea51e0-5f49-11e9-bd0b-00163e30eb10
Spec:
  Jobs:
    Name:         scale-down
    Schedule:     30 */1 * * * *
    Target Size:  1
    Name:         scale-up
    Schedule:     0 */1 * * * *
    Target Size:  3
  Scale Target Ref:
    API Version:  apps/v1beta2
    Kind:         Deployment
    Name:         nginx-deployment-basic
Status:
  Conditions:
    Job Id:           84818af0-3293-43e8-8ba6-6fd3ad2c35a4
    Last Probe Time:  2019-04-15T06:42:30Z
    Message:          cron hpa job scale-down executed successfully
    Name:             scale-down
    Schedule:         30 */1 * * * *
    State:            Succeed
    Job Id:           f8579f11-b129-4e72-b35f-c0bdd32583b3
    Last Probe Time:  2019-04-15T06:42:20Z
    Message:
    Name:             scale-up
    Schedule:         0 */1 * * * *
    State:            Submitted
Events:
  Type    Reason   Age   From                            Message
  ----    ------   ----  ----                            -------
  Normal  Succeed  5s    cron-horizontal-pod-autoscaler  cron hpa job scale-down executed successfully

🍻Cheers! It works.

Implementation Details

The following is an example of a CronHorizontalPodAutoscaler.

apiVersion: autoscaling.alibabacloud.com/v1beta1
kind: CronHorizontalPodAutoscaler
metadata:
  labels:
    controller-tools.k8s.io: "1.0"
  name: cronhpa-sample
  namespace: default 
spec:
   scaleTargetRef:
      apiVersion: apps/v1beta2
      kind: Deployment
      name: nginx-deployment-basic
   jobs:
   - name: "scale-down"
     schedule: "30 */1 * * * *"
     targetSize: 1
   - name: "scale-up"
     schedule: "0 */1 * * * *"
     targetSize: 3

The scaleTargetRef is the field to specify workload to scale. If the workload supports scale subresource(such as Deployment and StatefulSet), CronHorizontalPodAutoscaler should work well. CronHorizontalPodAutoscaler support multi cronhpa job in one spec.

The cronhpa job spec need three fields:

• name
  name should be unique in one cronhpa spec. You can distinguish different job execution status by job name.

• schedule
  The scheme of schedule is similar with crontab. kubernetes-cronhpa-controller use an enhanced cron golang lib （go-cron） which support more expressive rules.

  The cron expression format is as 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  | * / , - ?    
  

  Asterisk ( * )

  The asterisk indicates that the cron expression will match for all values of the field; e.g., using an asterisk in the 5th field (month) would indicate every month.

  Slash ( / )

  Slashes are used to describe increments of ranges. For example 3-59/15 in the 1st field (minutes) would indicate the 3rd minute of the hour and every 15 minutes thereafter. The form "*/..." is equivalent to the form "first-last/...", that is, an increment over the largest possible range of the field. The form "N/..." is accepted as meaning "N-MAX/...", that is, starting at N, use 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) would mean Mondays, Wednesdays and Fridays.

  Hyphen ( - )

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

  Question mark ( ? )

  Question mark may be used instead of '*' for leaving either day-of-month or day-of-week blank.

  more schedule scheme please check this doc.

• targetSize TargetSize is the size you desired to scale when the scheduled time arrive.

Common Question

• Cloud kubernetes-cronhpa-controller and HPA work together?
  Yes and no is the answer. kubernetes-cronhpa-controller can work together with hpa. But if the desired replicas is independent. So when the HPA min replicas reached kubernetes-cronhpa-controller will ignore the replicas and scale down and later the HPA controller will scale it up.

Contributing

Please check CONTRIBUTING.md

License

This software is released under the Apache 2.0 license.