CCE CronHPA Controller Description

Component introduction

The CCE-CronHPA-Controller (CronHPA Controller) allows users to define scheduled scaling rules via CRD. For applications with clear periodic workload patterns, it provides pre-scaling capabilities through the Container Cron Horizontal Pod Autoscaler.

Component function

• Scheduled scaling of the specified count of workload replicas

Application scenarios

• Cluster resources are managed based on a predefined schedule. CronHPA automatically initiates scaling-up or scaling-down actions at scheduled time points by configuring a series of tasks.
• Make sure system resources are appropriately configured and adjusted during spikes in user traffic to prevent service disruptions caused by scale-up delays.

Usage restrictions

• Only support Kubernetes clusters of v1.16 and above

Install component

1. Sign in to the Baidu AI Cloud official website and enter the management console.
2. Select Product Services > Cloud Native > Cloud Container Engine (CCE) to enter the CCE management console.
3. Click Cluster Management - Cluster List in the left navigation pane.
4. Click on the target cluster name in the Cluster List page to navigate to the cluster management page.
5. On the Cluster Management page, click Component Management.
6. In the component management list, select the CCE CronHPA Controller component and click Install
7. Click the OK button to finalize the component installation.

Deployment status

For installing the CCE CronHPA Controller component, the following objects will be deployed in the Kubernetes cluster:

Use

When deploying CronHPA to the cluster using YAML, the CCE CronHPA Controller monitors the CronHPA creation event and executes the corresponding logic.

Example of CronHPA template

1apiVersion: cce.baidubce.com/v1
2kind: CronHPA
3metadata:
4  name: cronhpa-sample
5spec:
6   scaleTargetRef:
7      apiVersion: apps/v1
8      kind: Deployment
9      name: nginx-deployment-basic
10   excludeDates:
11   - "* * * 15 11 *"
12   - "* * * 1 11 *"
13   crons:
14   - name: "scale-down"
15     schedule: "30 */1 * * * *"
16     targetSize: 1
17     runOnce: true
18   - name: "scale-up"
19     schedule: "01 */1 * * * *"
20     targetSize: 3

Introduction to deployment parameters

Among them, schedule and excludeDates need to be configured in the following format:

Special symbol description

• An asterisk (*) indicates that the field can match all possible values. For example, if an asterisk is used in the 5th field (month), it signifies every month.
• Slash (/) indicates an increment interval. For example, if the value of the first field (minutes) is 3-59/15, it means execution starts at the 3rd minute of each hour and repeats once every 15 minutes thereafter (i.e., executed at 3, 18, 33, 48 timepoints). This can also be expressed as: 3/15
• A comma (,) is used to specify enumerated values. For instance, if the value in the 6th field is MON,WED,FRI, it denotes execution on Monday, Wednesday, and Friday.
• Hyphen (-) indicates a range. For example, value of 9-17 in the third field means every hour from 9 am to 5 pm (including 9 and 17)
• Question mark (?) is only used for day of month and day of week. \ indicates no specified value and can be used to replace *

Example of cron

• Execute every 5 seconds: /5 * * * ?
• Execute every 1 minute: 0 /1 * * ?
• Execute once daily at 23:00: 0 0 23 * * ?
• Execute once daily at 1:00 AM: 0 0 1 * * ?
• Execute once at 1:00 AM on the 1st day of each month: 0 0 1 1 * ?
• Execute once at the 26th, 29th and 33rd minutes of each hour: 0 26,29,33 * * * ?
• Execute daily at 0:00, 13:00, 18:00, and 21:00: 0 0 0,13,18,21 * * ?

Example of CronHPA scaling for common objects

To apply CronHPA to a normal workload, you only need to configure the spec.scaleTargetRef field to the information of the workload. The following is a specific example of CronHPA scaling deployment:

1---
2apiVersion: apps/v1
3kind: Deployment
4metadata:
5  name: nginx-deployment-basic
6  labels:
7    app: nginx
8spec:
9  replicas: 2
10  selector:
11    matchLabels:
12      app: nginx
13  template:
14    metadata:
15      labels:
16        app: nginx
17    spec:
18      containers:
19      - name: nginx
20        image: nginx
21        ports:
22        - containerPort: 80
23---
24apiVersion: cce.baidubce.com/v1
25kind: CronHPA
26metadata:
27  name: cronhpa-sample
28spec:
29 scaleTargetRef: //Configure to the information of the above deployment
30    apiVersion: apps/v1
31    kind: Deployment
32    name: nginx-deployment-basic
33  crons:
34  - name: "scale-down"
35    schedule: "30 */1 * * * *"
36    targetSize: 1
37  - name: "scale-up"
38    schedule: "01 */1 * * * *"
39    targetSize: 3

CronHPA compatibility with HPA

It can be seen from the template definitions of CronHPA and HPA:

• Both CronHPA and HPA access the scaling object through the scaleTargetRef field.
• CronHPA adjusts the replica count periodically based on crontab rules.
• HPA determines scaling requirements based on resource utilization.

If both CronHPA and HPA are set, there will be a scenario where CronHPA and HPA operate on the same scaleTargetRef at the same time. CronHPA and HPA are independent of each other and cannot perceive each other. The later operation will overwrite the earlier one. For example, after a scheduled scale-up is completed, it may be scaled down due to low resource utilization. Therefore, when the object to be scaled is referenced by HPA, to avoid conflicts between HPA and CronHPA that cause the result to be overwritten, you need to configure spec.scaleTargetRef to the corresponding HPA object. In this way, CronHPA can perceive the status of HPA and adjust the replica count by adjusting the upper and lower limits of HPA.

Here are some specific scenario examples that are compatible with CronHPA and HPA to achieve scheduled scaling:

The following is a specific yaml example of CronHPA compatible with HPA:

1---
2apiVersion: autoscaling/v1
3kind: HorizontalPodAutoscaler
4metadata:
5  name: nginx-deployment-basic-hpa
6  namespace: default
7spec:
8  scaleTargetRef:
9    apiVersion: apps/v1
10    kind: Deployment
11    name: nginx-deployment-basic
12  minReplicas: 1
13  maxReplicas: 10
14  targetCPUUtilizationPercentage: 50
15---
16apiVersion: cce.baidubce.com/v1
17kind: CronHPA
18metadata:
19  name: cronhpa-sample
20spec:
21 scaleTargetRef:// Configure to the HPA object
22    apiVersion: autoscaling/v1
23    kind: HorizontalPodAutoscaler
24    name: nginx-deployment-basic-hpa
25  crons:
26    - name: "scale-down"
27      schedule: "30 */1 * * * *"
28      targetSize: 5
29      runOnce: false
30    - name: "scale-up"
31      schedule: "01 */1 * * * *"
32      targetSize: 10
33      runOnce: false

Version records