主打一手「Pod」管理。
一、背景
分佈式系統的一大優勢:可以針對不同的服務制定不同的管理策略,比如發佈、更新、下線,會根據服務自身的特點採取相應的措施;
如果服務的流量小,通常採取單服務部署即可,並且可以限定其資源分配;
如果服務的流量大並且是核心的能力,通常會採用集羣的方式管理,資源分配上也會更加的傾斜,從而保證核心應用的穩定性;
這種管理策略雖然很合理,但是從技術角度來看,其實現的複雜程度度也相對較高,在Kubenetes中可以使用Deployment組件簡化服務的編排難度;
二、Deployment組件
1、簡介
通過Deployment控制器,可以對應用進行快速的編排,比如聲明Pod的發佈方式,更新和回滾策略,維持Pod副本數量;
實際上控制器並不會直接管理Pod,而是通過管理ReplicaSet間接實現Pod管理,ReplicaSet是在後臺管理的Pod,在應用部署後可以查看相關的配置文件來驗證該流程;
2、語法說明
作爲K8S的工作負載(運行的應用程序)資源,Deployment爲Pod和ReplicaSet提供聲明式的管理能力;
這裏只是一個簡單的Deployment的yaml文件,作爲生產環境中最常用的部署方式,更多的細節可以參考K8S文檔;
三、基礎用例
1、創建操作
Deployment資源腳本,容器使用【auto-serve:latest】鏡像文件;
apiVersion: apps/v1
kind: Deployment
metadata:
name: serve-deployment
labels:
app: auto-serve
spec:
replicas: 2
selector:
matchLabels:
app: auto-serve
template:
metadata:
labels:
app: auto-serve
spec:
containers:
- name: auto-serve
image: auto-serve:latest
imagePullPolicy: Never
ports:
- containerPort: 8082
執行創建,然後在命令行或者控制檯界面查看相關結果;
kubectl apply -f serve-deployment.yaml
2、查看信息
查看指定【serve-deployment】信息;
kubectl get deployment/serve-deployment
NAME READY UP-TO-DATE AVAILABLE AGE
serve-deployment 2/2 2 2 5s
查看指定【serve-deployment】描述信息;
kubectl describe deployment/serve-deployment
Name: serve-deployment
Labels: app=auto-serve
Annotations: deployment.kubernetes.io/revision: 1
Selector: app=auto-serve
Replicas: 2 desired | 2 updated | 2 total | 2 available | 0 unavailable
StrategyType: RollingUpdate
Pod Template:
Labels: app=auto-serve
Containers:
auto-serve:
Image: auto-serve:latest
Port: 8082/TCP
Host Port: 0/TCP
Conditions:
Type Status Reason
---- ------ ------
Available True MinimumReplicasAvailable
Progressing True NewReplicaSetAvailable
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal ScalingReplicaSet 10m deployment-controller Scaled up replica set serve-deployment-f6f6c5bbd to 2
可以在控制檯界面查看【ReplicaSet】,或者直接從腳本文件查看相關信息;
查看上線狀態
kubectl rollout status deployment/serve-deployment
deployment "serve-deployment" successfully rolled out
查看【ReplicaSet】
kubectl get rs
NAME DESIRED CURRENT READY AGE
serve-deployment-f6f6c5bbd 2 2 2 12m
查看【Pod】
kubectl get pods
NAME READY STATUS RESTARTS AGE
serve-deployment-f6f6c5bbd-d8k6v 1/1 Running 0 15m
serve-deployment-f6f6c5bbd-hs6h5 1/1 Running 0 15m
3、更新操作
提供【auto-serve】多個版本的鏡像文件,用來模擬最常見的鏡像更新動作;
更新爲【1.1.1】鏡像版本
kubectl set image deployment/serve-deployment auto-serve=auto-serve:1.1.1
查看描述信息
kubectl describe deployment/serve-deployment
Name: serve-deployment
Labels: app=auto-serve
Annotations: 【deployment.kubernetes.io/revision: 2】對比此處和初次發佈的描述
Selector: app=auto-serve
Replicas: 2 desired | 2 updated | 2 total | 2 available | 0 unavailable
RollingUpdateStrategy: 25% max unavailable, 25% max surge
Pod Template:
Labels: app=auto-serve
Containers:
auto-serve:
Image: auto-serve:1.1.1 【鏡像已更新】
Port: 8082/TCP
Conditions:
Type Status Reason
---- ------ ------
Available True MinimumReplicasAvailable
Progressing True NewReplicaSetAvailable
NewReplicaSet: serve-deployment-6d9cd7f8c6 (2/2 replicas created)
4、刪除操作
kubectl delete -f serve-deployment.yaml
四、進階用例
1、回滾操作
再次執行鏡像更新,這樣【serve-deployment】會有3個版本
kubectl set image deployment/serve-deployment auto-serve=auto-serve:2.2.2
查看歷史版本
kubectl rollout history deployment/serve-deployment
deployment.apps/serve-deployment
REVISION CHANGE-CAUSE
1 <none>
2 <none>
3 <none>
查看歷史版本2信息,【auto-serve】對應的鏡像版本是【1.1.1】
kubectl rollout history deployment/serve-deployment --revision=2
deployment.apps/serve-deployment with revision #2
Pod Template:
Labels: app=auto-serve
pod-template-hash=6d9cd7f8c6
Containers:
auto-serve:
Image: auto-serve:1.1.1
Port: 8082/TCP
Host Port: 0/TCP
Environment: <none>
Mounts: <none>
Volumes: <none>
回滾到上個版本,即鏡像【auto-serve:1.1.1】
kubectl rollout undo deployment/serve-deployment
deployment.apps/serve-deployment rolled back
回滾到指定版本,即鏡像【auto-serve:latest】
kubectl rollout undo deployment/serve-deployment --to-revision=1
2、伸縮操作
伸縮命令
kubectl scale deployment/serve-deployment --replicas=3
deployment.apps/serve-deployment scaled
查看【ReplicaSet】信息
kubectl get rs
NAME DESIRED CURRENT READY AGE
serve-deployment-6b47bf4db7 0 0 0 7m3s
serve-deployment-6d9cd7f8c6 0 0 0 7m17s
serve-deployment-f6f6c5bbd 3 3 3 8m10s
查看【Pod】信息
kubectl get pods
NAME READY STATUS RESTARTS AGE
serve-deployment-f6f6c5bbd-4rvhw 1/1 Running 0 4m13s
serve-deployment-f6f6c5bbd-bwg7s 1/1 Running 0 4m15s
serve-deployment-f6f6c5bbd-mv9wt 1/1 Running 0 2m21s
3、暫停與恢復
暫停發佈
kubectl rollout pause deployment/serve-deployment
deployment.apps/serve-deployment paused
查看信息描述
kubectl describe deployment/serve-deployment
Conditions:
Type Status Reason
---- ------ ------
Available True MinimumReplicasAvailable
Progressing Unknown DeploymentPaused 【注意此處的狀態】
執行更新
kubectl set image deployment/serve-deployment auto-serve=auto-serve:1.1.1
查看Pod,未觸發上線
恢復發佈,會自動執行上面的更新動作
kubectl rollout resume deployment/serve-deployment
查看【ReplicaSet】信息
kubectl get rs -o wide
NAME DESIRED CURRENT READY AGE CONTAINERS IMAGES
serve-deployment-6b47bf4db7 0 0 0 14m auto-serve auto-serve:2.2.2
serve-deployment-6d9cd7f8c6 3 3 3 15m auto-serve auto-serve:1.1.1
serve-deployment-f6f6c5bbd 0 0 0 16m auto-serve auto-serve:latest
查看【Pod】信息
kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE
serve-deployment-6d9cd7f8c6-m66cv 1/1 Running 0 2m9s 10.1.0.125 docker-desktop
serve-deployment-6d9cd7f8c6-sk2qv 1/1 Running 0 2m11s 10.1.0.124 docker-desktop
serve-deployment-6d9cd7f8c6-zj6p2 1/1 Running 0 2m8s 10.1.0.126 docker-desktop
五、狀態描述
Deployment有三個核心狀態來描述其生命週期的變化:「Progressing」進行中,「Complete」已完成,「Failed」失敗;
【Progressing】
Deployment處在部署或者伸縮過程中;
當Deployment執行這些任務期間:創建新的ReplicaSet;正在爲其最新的ReplicaSet擴容;正在爲其舊有的ReplicaSets縮容;新的Pod已經就緒或者可用;
【Complete】
具有以下特徵時會被標記爲已完成狀態;
Deployment關聯的所有副本都已更新到指定的最新版本,意味着此前請求的所有更新都已完成;Deployment關聯的所有副本都可用;未運行Deployment的舊副本;
【Failed】
Deployment可能會在嘗試部署其最新的ReplicaSet受挫,一直處於未完成狀態;
造成這種情況的因素很多,可能是:配額不足,就緒探測失敗,鏡像拉取錯誤,權限不足,限制範圍問題,應用程序運行時的配置錯誤;
六、參考源碼
文檔倉庫:
https://gitee.com/cicadasmile/butte-java-note
腳本倉庫:
https://gitee.com/cicadasmile/butte-auto-parent