前言
定時伸縮（cronhpa）是很多開發者在解決負載週期性時最常用的方法，通過類似crontab的語法可以在一個時間點定時觸發伸縮活動。crontab的語義表達是很強大的，但是也存在語法複雜，執行計劃容易被打斷等問題。為了解決上述的問題，定時伸縮（cronhpa）提供了運維模式，支持通過運維頁面來查看底層排隊的定時任務，同時也提供了API接口用於開發者自研的平臺接入與集成。
定時伸縮組件運維模式介紹
當通過ACK的應用目錄或者開源社區的模板下發最新版本定時伸縮組件（cronhpa）後，默認在8000端口就已經開啟了運維模式。我們先給定時伸縮組件（cronhpa）創建一個svc用來訪問運維頁面。
apiVersion: v1
kind: Service
metadata:
name: kubernetes-cronhpa-controller
namespace: kube-system
spec:
ports:
- port: 80
protocol: TCP
targetPort: 8000
selector:
app: ack-kubernetes-cronhpa-controller
sessionAffinity: None
type: ClusterIP此時，在本地我們可以通過執行kubectl proxy --port=8080啟動proxy模式，再在本地瀏覽器中輸入http://localhost:8080/api/v1/namespaces/kube-system/services/kubernetes-cronhpa-controller/proxy/ 即可訪問運維管理頁面。
讓我們來解析下這個頁面中展現的字段和使用的方式。
- CronHPA：定時伸縮CRD的名字。
- Namespace：定時伸縮CRD的命名空間。
- Id：伸縮任務的唯一Id，這個Id的作用是唯一決定一個任務的信息。
當CRD中出現了JobId與底層CronEngine中的Id不匹配的情況，說明CRD中的任務沒有及時被下發到底層的定時執行引擎中，此時就需要特別關注下定時伸縮（cronhpa）組件穩定性的問題了。
- Pre：上一次任務執行的時間，如果這個數值是初始時間（0001-01-01 00:00:00 +0000 UTC）說明任務還沒有被執行過。
- Next：下一次任務執行的時間，用來確認定時引擎中是否已經有正確排隊的任務。
通常情況下，我們只需要通過頁面大盤確認下發的作業已經存在，並且Pre/Next這兩個字段是正常的狀態，基本就可以確認定時任務可以正常執行了。如果開發者有自己的運維管理系統，可以使用API的方式進行接入。接口地址：http://localhost:8080/api/v1/namespaces/kube-system/services/kubernetes-cronhpa-controller/proxy/api.json
[
{
"Schedule": {
"Second": 1073741824,
"Minute": 10376293541461622783,
"Hour": 9223372036871553023,
"Dom": 9223372041149743102,
"Month": 9223372036854783998,
"Dow": 9223372036854775935
},
"Next": "2021-03-15T18:53:30+08:00",
"Prev": "2021-03-15T18:52:30+08:00",
"Job": {
"TargetRef": {
"RefName": "nginx-deployment-basic",
"RefNamespace": "default",
"RefKind": "Deployment",
"RefGroup": "apps",
"RefVersion": "v1"
},
"HPARef": {
"kind": "CronHorizontalPodAutoscaler",
"apiVersion": "autoscaling.alibabacloud.com/v1beta1",
"metadata": {
"name": "cronhpa-sample",
"namespace": "default",
"selfLink": "/apis/autoscaling.alibabacloud.com/v1beta1/namespaces/default/cronhorizontalpodautoscalers/cronhpa-sample",
"uid": "54dc98fe-b311-4763-8d99-25a93bdf5c74",
"resourceVersion": "770255389",
"generation": 2,
"creationTimestamp": "2021-03-15T10:49:46Z",
"labels": {
"controller-tools.k8s.io": "1.0"
},
"annotations": {
"kubectl.kubernetes.io/last-applied-configuration": "{\"apiVersion\":\"autoscaling.alibabacloud.com/v1beta1\",\"kind\":\"CronHorizontalPodAutoscaler\",\"metadata\":{\"annotations\":{},\"labels\":{\"controller-tools.k8s.io\":\"1.0\"},\"name\":\"cronhpa-sample\",\"namespace\":\"default\"},\"spec\":{\"jobs\":[{\"name\":\"scale-down\",\"schedule\":\"30 */1 * * * *\",\"targetSize\":1},{\"name\":\"scale-up\",\"schedule\":\"01 */1 * * * *\",\"targetSize\":3}],\"scaleTargetRef\":{\"apiVersion\":\"apps/v1\",\"kind\":\"Deployment\",\"name\":\"nginx-deployment-basic\"}}}\n"
}
},
"spec": {
"scaleTargetRef": {
"apiVersion": "apps/v1",
"kind": "Deployment",
"name": "nginx-deployment-basic"
},
"jobs": [
{
"name": "scale-down",
"schedule": "30 */1 * * * *",
"targetSize": 1
},
{
"name": "scale-up",
"schedule": "01 */1 * * * *",
"targetSize": 3
}
]
},
"status": {
"scaleTargetRef": {
"apiVersion": "apps/v1",
"kind": "Deployment",
"name": "nginx-deployment-basic"
},
"conditions": [
{
"name": "scale-down",
"jobId": "f68e5d16-f92b-4456-89d0-1da3ca36efa4",
"schedule": "30 */1 * * * *",
"targetSize": 1,
"runOnce": false,
"state": "Submitted",
"lastProbeTime": "2021-03-15T10:49:46Z",
"message": ""
},
{
"name": "scale-up",
"jobId": "8f611afa-ebde-4903-8c23-b323951b8757",
"schedule": "01 */1 * * * *",
"targetSize": 3,
"runOnce": false,
"state": "Submitted",
"lastProbeTime": "2021-03-15T10:49:46Z",
"message": ""
}
]
}
},
"DesiredSize": 1,
"Plan": "30 */1 * * * *",
"RunOnce": false
}
},
{
"Schedule": {
"Second": 2,
"Minute": 10376293541461622783,
"Hour": 9223372036871553023,
"Dom": 9223372041149743102,
"Month": 9223372036854783998,
"Dow": 9223372036854775935
},
"Next": "2021-03-15T18:54:01+08:00",
"Prev": "2021-03-15T18:53:01+08:00",
"Job": {
"TargetRef": {
"RefName": "nginx-deployment-basic",
"RefNamespace": "default",
"RefKind": "Deployment",
"RefGroup": "apps",
"RefVersion": "v1"
},
"HPARef": {
"kind": "CronHorizontalPodAutoscaler",
"apiVersion": "autoscaling.alibabacloud.com/v1beta1",
"metadata": {
"name": "cronhpa-sample",
"namespace": "default",
"selfLink": "/apis/autoscaling.alibabacloud.com/v1beta1/namespaces/default/cronhorizontalpodautoscalers/cronhpa-sample",
"uid": "54dc98fe-b311-4763-8d99-25a93bdf5c74",
"resourceVersion": "770255389",
"generation": 2,
"creationTimestamp": "2021-03-15T10:49:46Z",
"labels": {
"controller-tools.k8s.io": "1.0"
},
"annotations": {
"kubectl.kubernetes.io/last-applied-configuration": "{\"apiVersion\":\"autoscaling.alibabacloud.com/v1beta1\",\"kind\":\"CronHorizontalPodAutoscaler\",\"metadata\":{\"annotations\":{},\"labels\":{\"controller-tools.k8s.io\":\"1.0\"},\"name\":\"cronhpa-sample\",\"namespace\":\"default\"},\"spec\":{\"jobs\":[{\"name\":\"scale-down\",\"schedule\":\"30 */1 * * * *\",\"targetSize\":1},{\"name\":\"scale-up\",\"schedule\":\"01 */1 * * * *\",\"targetSize\":3}],\"scaleTargetRef\":{\"apiVersion\":\"apps/v1\",\"kind\":\"Deployment\",\"name\":\"nginx-deployment-basic\"}}}\n"
}
},
"spec": {
"scaleTargetRef": {
"apiVersion": "apps/v1",
"kind": "Deployment",
"name": "nginx-deployment-basic"
},
"jobs": [
{
"name": "scale-down",
"schedule": "30 */1 * * * *",
"targetSize": 1
},
{
"name": "scale-up",
"schedule": "01 */1 * * * *",
"targetSize": 3
}
]
},
"status": {
"scaleTargetRef": {
"apiVersion": "apps/v1",
"kind": "Deployment",
"name": "nginx-deployment-basic"
},
"conditions": [
{
"name": "scale-down",
"jobId": "f68e5d16-f92b-4456-89d0-1da3ca36efa4",
"schedule": "30 */1 * * * *",
"targetSize": 1,
"runOnce": false,
"state": "Submitted",
"lastProbeTime": "2021-03-15T10:49:46Z",
"message": ""
},
{
"name": "scale-up",
"jobId": "8f611afa-ebde-4903-8c23-b323951b8757",
"schedule": "01 */1 * * * *",
"targetSize": 3,
"runOnce": false,
"state": "Submitted",
"lastProbeTime": "2021-03-15T10:49:46Z",
"message": ""
}
]
}
},
"DesiredSize": 3,
"Plan": "01 */1 * * * *",
"RunOnce": false
}
}
]最後
通過運維頁面和API，開發者可以很好地洞悉定時伸縮（cronhpa）組件的底層狀態，提供更確切的伸縮保障。如果對於運維模式有更多的建議，請提交到社區。
