在 kubernetes 初始部署中如何对副本进行排序

Question

我有一个 pod，它带有一个连接到外部数据库的应用程序服务器。为了冗余，我想运行多个 pods，因此我使用 rolingupdate 策略（maxSurge = 1 和 maxUnavailable = 1）将部署扩展到 3 个。

有时（大部分时间）pods 在第一次创建时失败，因为我使用的是 liquibase，并且所有 pods 尝试同时锁定数据库。

对我来说最简单的解决方案似乎是 pods 按顺序启动。所以启动 pod 1，等待 60 秒，然后启动 pod 2 等

这是一个有效的解决方案吗？我怎样才能在 k8s (v1.14) 中实现它？

这是 kubectl describe deploy 的输出：

Name:                   jx-apollon
Namespace:              jx-staging
CreationTimestamp:      Sun, 27 Oct 2019 21:28:07 +0100
Labels:                 chart=apollon-1.0.348
                        draft=draft-app
                        jenkins.io/chart-release=jx
                        jenkins.io/namespace=jx-staging
                        jenkins.io/version=4
Annotations:            deployment.kubernetes.io/revision: 3
                        jenkins.io/chart: env
                        kubectl.kubernetes.io/last-applied-configuration:
                          {"apiVersion":"extensions/v1beta1","kind":"Deployment","metadata":{"annotations":{"jenkins.io/chart":"env"},"labels":{"chart":"apollon-1.0...
Selector:               app=jx-apollon,draft=draft-app
Replicas:               0 desired | 0 updated | 0 total | 0 available | 0 unavailable
StrategyType:           RollingUpdate
MinReadySeconds:        0
RollingUpdateStrategy:  1 max unavailable, 1 max surge
Pod Template:
  Labels:  app=jx-apollon
           draft=draft-app
  Init Containers:
   postgres-listener-short:
    Image:      alpine
    Port:       <none>
    Host Port:  <none>
    Command:
      sh
      -c
      echo 'Waiting in init container for DB to become available.'; echo $DB; for i in $(seq 1 5); do echo 'nc ping' $i && nc -z -w3 $DB 5432 && echo 'DB is available, continuing now to application initialization.' && exit 0 || sleep 3; done; echo 'DB is not yet available.'; exit 1
    Environment:
      DB:    jx-apollon-postgresql-db-alias
    Mounts:  <none>
   postgres-listener-longer:
    Image:      alpine
    Port:       <none>
    Host Port:  <none>
    Command:
      sh
      -c
      echo 'Waiting in init container for DB to become available.'; echo $DB; for i in $(seq 1 100); do echo 'nc ping' $i && nc -z -w3 $DB 5432 && echo 'DB is available, continuing now to application initialization.' && exit 0 || sleep 3; done; echo 'DB is not yet available.'; exit 1
    Environment:
      DB:    jx-apollon-postgresql-db-alias
    Mounts:  <none>
  Containers:
   apollon:
    Image:       <redacted>
    Ports:       8080/TCP, 8443/TCP
    Host Ports:  0/TCP, 0/TCP
    Limits:
      cpu:     2
      memory:  6Gi
    Requests:
      cpu:      100m
      memory:   3584Mi
    Liveness:   http-get http://:8080/ delay=60s timeout=1s period=10s #success=1 #failure=3
    Readiness:  http-get http://:8080/ delay=0s timeout=1s period=10s #success=1 #failure=3
    Environment:
      DB:                 jx-apollon-postgresql-db-alias
      POSTGRES_PASSWORD:  <redacted>
      RULES_CLIENT:       demo
      _JAVA_OPTIONS:      -XX:+UseContainerSupport -XX:MaxRAMPercentage=90.0 -XX:+UseG1GC
    Mounts:               <none>
  Volumes:                <none>
Conditions:
  Type           Status  Reason
  ----           ------  ------
  Available      True    MinimumReplicasAvailable
OldReplicaSets:  <none>
NewReplicaSet:   jx-apollon-95b4c77cb (0/0 replicas created)
Events:          <none>

Answer 1

我将 initContainer 部分更改为这段代码，它一直等到它从 liquibase 创建的数据库更改日志锁 table 中读取错误值。

      initContainers:
      - name: postgres-listener
        image: postgres
        env:
        - name: DB
          value: jx-apollon-postgresql-db-alias
        command: ['sh', '-c', '\
         until psql -qtAX -h $DB -d postgres -c \ 
         "select count(locked) from databasechangeloglock where locked = false group by locked"; 
         do echo  waiting for dbchangeloglock of postgres db to be false; sleep 2; done;
         ']

在 kubernetes 初始部署中如何对副本进行排序

On kubernetes inital deployment how to sequence replica's

liquibase

kubernetes