postgresql – 在Kubernetes集群上管理数据库迁移

我有一个基于Kubernetes的应用程序,由多个服务(和pod)管理,带有掌舵图.

Postgres用作所有服务的数据库.

当应用程序升级到更新版本时,我通过initContainers运行数据库迁移脚本.

当迁移脚本需要对DB的独占访问(应终止所有其他连接)时,会出现此问题,否则会阻止脚本.

理想的解决方案是停止所有pod,运行迁移并重新创建它们.但我不确定如何使用Kubernetes正确实现它.

TNX

解决方法

Ideal solution would be to stop all pods,run the migration and
recreate them. But I am not sure how to achieve it properly with
Kubernetes.

我从其中一条评论中看到你使用Helm,所以我想提出一个利用Helm钩子的解决方案：

Helm provides a hook mechanism to allow chart developers to intervene
at certain points in a release’s life cycle. For example,you can use
hooks to:

• Load a ConfigMap or Secret during install before any other charts are
  loaded.

• Execute a Job to back up a database before installing a new
  chart,and then execute a second job after the upgrade in order to
  restore data.

• Run a Job before deleting a release to gracefully take a
  service out of rotation before removing it.

https://github.com/kubernetes/helm/blob/master/docs/charts_hooks.md

您可以将迁移打包为k8s作业,并利用预安装或升级前挂钩来运行作业.这些钩子在渲染模板后运行,但在Kubernetes中创建任何新资源之前运行.因此,您的迁移将在部署Pod之前运行.

要在运行迁移之前删除部署,请使用较低的helm.sh/hook-weight创建第二个预安装/升级前挂钩,以删除目标部署：

apiVersion: batch/v1
kind: Job
metadata:
  name: "pre-upgrade-hook1"
  annotations:
    "helm.sh/hook": pre-upgrade
    "helm.sh/hook-weight": "-1"
    "helm.sh/hook-delete-policy": hook-succeeded
spec:
  template:
    metadata:
      name: "pre-upgrade-hook1"
    spec:
      restartPolicy: Never
      serviceAccountName: "<an SA with delete RBAC permissions>"
      containers:
      - name: kubectl
        image: "lachlanevenson/k8s-kubectl:latest"
        command: ["delete","deployment","deploy1","deploy2"]

较低的钩子重量将确保此作业在迁移作业之前运行.这将确保以下一系列事件：

>你运行头盔升级
>具有最低挂钩权重的helm挂钩运行并删除相关部署
>第二个钩子运行并运行您的迁移
>您的图表将安装新的Deployments,Pods等.

只需确保将所有相关的部署保留在同一个图表中.