--- # System prepended metadata title: Deployment strategy tags: [K8S] --- # Deployment strategy * Kubernetes 在計算 availableReplicas 數值時不考慮終止過程中的 Pod， availableReplicas 的值一定介於 replicas - maxUnavailable 和 replicas + maxSurge 之間。 因此，你可能在上線期間看到 Pod 個數比預期的多，Deployment 所消耗的總的資源也大於 replicas + maxSurge 個 Pod 所用的資源，直到被終止的 Pod 所設定的 terminationGracePeriodSeconds 到期為止。 ``` # maxSurge、maxUnavailable 可以用數字和 % 宣告，如果使用數字宣告，單位就是 pod 的個數 # maxSurge 代表是在 rolling update 過程中可以創建的額外 Pod 的最大數量或百分比 # maxUnavailable 代表是在 rolling update 過程中允許不可用的 Pod 的最大數量或百分比 $ echo 'apiVersion: apps/v1 kind: Deployment metadata: creationTimestamp: null labels: app: test name: test spec: replicas: 5 selector: matchLabels: app: test strategy: rollingUpdate: maxSurge: 1 # 可以多出一個 pod maxUnavailable: 1 # 允許一個不可提供服務的 pod template: metadata: creationTimestamp: null labels: app: test spec: containers: - image: quay.io/cloudwalker/nginx name: nginx resources: {} status: {}' | kubectl apply -f - ``` * 使用 rollout 更新 deploy ``` $ kubectl rollout restart deploy test ``` * deployment 會去呼叫新的 replica 多長出一個 pod，之後就再叫舊的 replica 減少一個 pod，以此類推 ``` $ kubectl describe deploy test ...... Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal ScalingReplicaSet 54s deployment-controller Scaled up replica set test-6477f8d8fd to 5 Normal ScalingReplicaSet 33s deployment-controller Scaled up replica set test-6d7487958d to 1 Normal ScalingReplicaSet 33s deployment-controller Scaled down replica set test-6477f8d8fd to 4 from 5 Normal ScalingReplicaSet 32s deployment-controller Scaled up replica set test-6d7487958d to 2 from 1 Normal ScalingReplicaSet 30s deployment-controller Scaled down replica set test-6477f8d8fd to 3 from 4 Normal ScalingReplicaSet 30s deployment-controller Scaled up replica set test-6d7487958d to 3 from 2 Normal ScalingReplicaSet 28s deployment-controller Scaled down replica set test-6477f8d8fd to 2 from 3 Normal ScalingReplicaSet 28s deployment-controller Scaled up replica set test-6d7487958d to 4 from 3 Normal ScalingReplicaSet 26s deployment-controller Scaled down replica set test-6477f8d8fd to 1 from 2 Normal ScalingReplicaSet 22s (x2 over 26s) deployment-controller (combined from similar events): Scaled down replica set test-6477f8d8fd to 0 from 1 ``` * 刪除 deployment ``` $ kubectl delete deploy test ``` ### 測試 maxSurge 設為 2 ``` $ echo 'apiVersion: apps/v1 kind: Deployment metadata: creationTimestamp: null labels: app: test name: test spec: replicas: 5 selector: matchLabels: app: test strategy: rollingUpdate: maxSurge: 2 maxUnavailable: 1 template: metadata: creationTimestamp: null labels: app: test spec: containers: - image: quay.io/cloudwalker/nginx name: nginx resources: {} status: {}' | kubectl apply -f - ``` * 使用 rollout 更新 deploy ``` $ kubectl rollout restart deploy test ``` * 可以發現 deployment 第一次呼叫新的 replica 會直接多兩個 pod，但是由於刪除舊的 pod 只有一個，因此第二次新的 replica 只有長出一個 pod。 * pod 數量需要符合 replicas - maxUnavailable 和 replicas + maxSurge 之間，以此題為例， pod 數量就是 4~7 之間。 ``` $ kubectl describe deploy test ...... Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal ScalingReplicaSet 46s deployment-controller Scaled up replica set test-6477f8d8fd to 5 Normal ScalingReplicaSet 18s deployment-controller Scaled up replica set test-77b9c86d to 2 Normal ScalingReplicaSet 18s deployment-controller Scaled down replica set test-6477f8d8fd to 4 from 5 Normal ScalingReplicaSet 17s deployment-controller Scaled up replica set test-77b9c86d to 3 from 2 Normal ScalingReplicaSet 15s deployment-controller Scaled down replica set test-6477f8d8fd to 3 from 4 Normal ScalingReplicaSet 15s deployment-controller Scaled up replica set test-77b9c86d to 4 from 3 Normal ScalingReplicaSet 11s deployment-controller Scaled down replica set test-6477f8d8fd to 2 from 3 Normal ScalingReplicaSet 11s deployment-controller Scaled up replica set test-77b9c86d to 5 from 4 Normal ScalingReplicaSet 11s deployment-controller Scaled down replica set test-6477f8d8fd to 1 from 2 Normal ScalingReplicaSet 9s deployment-controller (combined from similar events): Scaled down replica set test-6477f8d8fd to 0 from 1 ``` * 刪除 deployment ``` $ kubectl delete deploy test ``` ### 測試 maxSurge 設為 1 maxUnavailable 設為 0 ``` $ echo 'apiVersion: apps/v1 kind: Deployment metadata: creationTimestamp: null labels: app: test name: test spec: replicas: 5 selector: matchLabels: app: test strategy: rollingUpdate: maxSurge: 1 maxUnavailable: 0 template: metadata: creationTimestamp: null labels: app: test spec: containers: - image: quay.io/cloudwalker/nginx name: nginx resources: {} status: {}' | kubectl apply -f - ``` ``` $ kubectl rollout restart deploy test ``` ``` $ kubectl describe deploy test ...... Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal ScalingReplicaSet 22s deployment-controller Scaled up replica set test-86f864c84c to 5 Normal ScalingReplicaSet 10s deployment-controller Scaled up replica set test-6c754cf5f6 to 1 Normal ScalingReplicaSet 8s deployment-controller Scaled down replica set test-86f864c84c to 4 from 5 Normal ScalingReplicaSet 8s deployment-controller Scaled up replica set test-6c754cf5f6 to 2 from 1 Normal ScalingReplicaSet 5s deployment-controller Scaled down replica set test-86f864c84c to 3 from 4 Normal ScalingReplicaSet 5s deployment-controller Scaled up replica set test-6c754cf5f6 to 3 from 2 Normal ScalingReplicaSet 3s deployment-controller Scaled down replica set test-86f864c84c to 2 from 3 Normal ScalingReplicaSet 3s deployment-controller Scaled up replica set test-6c754cf5f6 to 4 from 3 Normal ScalingReplicaSet 1s deployment-controller Scaled down replica set test-86f864c84c to 1 from 2 Normal ScalingReplicaSet 1s deployment-controller (combined from similar events): Scaled up replica set test-6c754cf5f6 to 5 from 4 ``` * 刪除 deployment ``` $ kubectl delete deploy test ``` ### 測試 maxSurge 設為 0 maxUnavailable 設為 1 ``` $ echo 'apiVersion: apps/v1 kind: Deployment metadata: creationTimestamp: null labels: app: test name: test spec: replicas: 1 selector: matchLabels: app: test strategy: rollingUpdate: maxSurge: 0 maxUnavailable: 1 template: metadata: creationTimestamp: null labels: app: test spec: containers: - image: quay.io/cloudwalker/nginx name: nginx resources: {} status: {}' | kubectl apply -f - ``` ``` $ kubectl rollout restart deploy test ``` * 會先刪除原本的 pod 在建立新的 pod ``` $ kubectl describe deploy test ...... Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal ScalingReplicaSet 37s deployment-controller Scaled up replica set test-86f864c84c to 5 Normal ScalingReplicaSet 23s deployment-controller Scaled down replica set test-86f864c84c to 4 from 5 Normal ScalingReplicaSet 23s deployment-controller Scaled up replica set test-5b97f75c85 to 1 from 0 Normal ScalingReplicaSet 20s deployment-controller Scaled down replica set test-86f864c84c to 3 from 4 Normal ScalingReplicaSet 20s deployment-controller Scaled up replica set test-5b97f75c85 to 2 from 1 Normal ScalingReplicaSet 18s deployment-controller Scaled down replica set test-86f864c84c to 2 from 3 Normal ScalingReplicaSet 18s deployment-controller Scaled up replica set test-5b97f75c85 to 3 from 2 Normal ScalingReplicaSet 16s deployment-controller Scaled down replica set test-86f864c84c to 1 from 2 Normal ScalingReplicaSet 16s deployment-controller Scaled up replica set test-5b97f75c85 to 4 from 3 Normal ScalingReplicaSet 14s (x2 over 14s) deployment-controller (combined from similar events): Scaled up replica set test-5b97f75c85 to 5 from 4 ``` ## 參考文件 https://medium.com/@bubu.tripathy/understanding-maxsurge-and-maxunavailable-4966dfafc8ba https://kubernetes.io/zh-cn/docs/concepts/workloads/controllers/deployment/