Kubernetes 不会在可用节点之间传播 Pod

Question

我有一个带有大小为 2 的单节点池的 GKE 集群。当我添加第三个节点时，没有任何 Pod 分发到第三个节点。

这是原始的 2 节点节点池：

$ kubectl get node
NAME                              STATUS    ROLES     AGE       VERSION
gke-cluster0-pool-d59e9506-b7nb   Ready     <none>    13m       v1.8.3-gke.0
gke-cluster0-pool-d59e9506-vp6t   Ready     <none>    18m       v1.8.3-gke.0

这是在原始节点池上运行的 pod：

$ kubectl get po -o wide --all-namespaces
NAMESPACE     NAME                                         READY     STATUS      RESTARTS   AGE       IP           NODE
default       attachment-proxy-659bdc84d-ckdq9             1/1       Running     0          10m       10.0.38.3    gke-cluster0-pool-d59e9506-vp6t
default       elasticsearch-0                              1/1       Running     0          4m        10.0.39.11   gke-cluster0-pool-d59e9506-b7nb
default       front-webapp-646bc49675-86jj6                1/1       Running     0          10m       10.0.38.10   gke-cluster0-pool-d59e9506-vp6t
default       kafka-0                                      1/1       Running     3          4m        10.0.39.9    gke-cluster0-pool-d59e9506-b7nb
default       mailgun-http-98f8d997c-hhfdc                 1/1       Running     0          4m        10.0.38.17   gke-cluster0-pool-d59e9506-vp6t
default       stamps-5b6fc489bc-6xtqz                      2/2       Running        3          10m       10.0.38.13   gke-cluster0-pool-d59e9506-vp6t
default       user-elasticsearch-6b6dd7fc8-b55xx           1/1       Running     0          10m       10.0.38.4    gke-cluster0-pool-d59e9506-vp6t
default       user-http-analytics-6bdd49bd98-p5pd5         1/1       Running     0          4m        10.0.39.8    gke-cluster0-pool-d59e9506-b7nb
default       user-http-graphql-67884c678c-7dcdq           1/1       Running     0          4m        10.0.39.7    gke-cluster0-pool-d59e9506-b7nb
default       user-service-5cbb8cfb4f-t6zhv                1/1       Running     0          4m        10.0.38.15   gke-cluster0-pool-d59e9506-vp6t
default       user-streams-0                               1/1       Running     0          4m        10.0.39.10   gke-cluster0-pool-d59e9506-b7nb
default       user-streams-elasticsearch-c64b64d6f-2nrtl   1/1       Running     3          10m       10.0.38.6    gke-cluster0-pool-d59e9506-vp6t
default       zookeeper-0                                  1/1       Running     0          4m        10.0.39.12   gke-cluster0-pool-d59e9506-b7nb
kube-lego     kube-lego-7799f6b457-skkrc                   1/1       Running     0          10m       10.0.38.5    gke-cluster0-pool-d59e9506-vp6t
kube-system   event-exporter-v0.1.7-7cb7c5d4bf-vr52v       2/2       Running     0          10m       10.0.38.7    gke-cluster0-pool-d59e9506-vp6t
kube-system   fluentd-gcp-v2.0.9-648rh                     2/2       Running     0          14m       10.0.38.2    gke-cluster0-pool-d59e9506-vp6t
kube-system   fluentd-gcp-v2.0.9-fqjz6                     2/2       Running     0          9m        10.0.39.2    gke-cluster0-pool-d59e9506-b7nb
kube-system   heapster-v1.4.3-6fc45b6cc4-8cl72             3/3       Running     0          4m        10.0.39.6    gke-cluster0-pool-d59e9506-b7nb
kube-system   k8s-snapshots-5699c68696-h8r75               1/1       Running     0          4m        10.0.38.16   gke-cluster0-pool-d59e9506-vp6t
kube-system   kube-dns-778977457c-b48w5                    3/3       Running     0          4m        10.0.39.5    gke-cluster0-pool-d59e9506-b7nb
kube-system   kube-dns-778977457c-sw672                    3/3       Running     0          10m       10.0.38.9    gke-cluster0-pool-d59e9506-vp6t
kube-system   kube-dns-autoscaler-7db47cb9b7-tjt4l         1/1       Running     0          10m       10.0.38.11   gke-cluster0-pool-d59e9506-vp6t
kube-system   kube-proxy-gke-cluster0-pool-d59e9506-b7nb   1/1       Running     0          9m        10.128.0.4   gke-cluster0-pool-d59e9506-b7nb
kube-system   kube-proxy-gke-cluster0-pool-d59e9506-vp6t   1/1       Running     0          14m       10.128.0.2   gke-cluster0-pool-d59e9506-vp6t
kube-system   kubernetes-dashboard-76c679977c-mwqlv        1/1       Running     0          10m       10.0.38.8    gke-cluster0-pool-d59e9506-vp6t
kube-system   l7-default-backend-6497bcdb4d-wkx28          1/1       Running     0          10m       10.0.38.12   gke-cluster0-pool-d59e9506-vp6t
kube-system   nginx-ingress-controller-78d546664f-gf6mx    1/1       Running     0          4m        10.0.39.3    gke-cluster0-pool-d59e9506-b7nb
kube-system   tiller-deploy-5458cb4cc-26x26                1/1       Running     0          4m        10.0.39.4    gke-cluster0-pool-d59e9506-b7nb

然后我将另一个节点添加到节点池中：

gcloud container clusters resize cluster0 --node-pool pool --size 3

第三个已添加并准备就绪：

NAME                              STATUS    ROLES     AGE       VERSION
gke-cluster0-pool-d59e9506-1rzm   Ready     <none>    3m        v1.8.3-gke.0
gke-cluster0-pool-d59e9506-b7nb   Ready     <none>    14m       v1.8.3-gke.0
gke-cluster0-pool-d59e9506-vp6t   Ready     <none>    19m       v1.8.3-gke.0

但是，除了属于的 pod 之外，没有任何 podDaemonSet被调度到添加的节点上：

$ kubectl get po -o wide --all-namespaces
NAMESPACE     NAME                                         READY     STATUS      RESTARTS   AGE       IP           NODE
default       attachment-proxy-659bdc84d-ckdq9             1/1       Running     0          17m       10.0.38.3    gke-cluster0-pool-d59e9506-vp6t
default       elasticsearch-0                              1/1       Running     0          10m       10.0.39.11   gke-cluster0-pool-d59e9506-b7nb
default       front-webapp-646bc49675-86jj6                1/1       Running     0          17m       10.0.38.10   gke-cluster0-pool-d59e9506-vp6t
default       kafka-0                                      1/1       Running     3          11m       10.0.39.9    gke-cluster0-pool-d59e9506-b7nb
default       mailgun-http-98f8d997c-hhfdc                 1/1       Running     0          10m       10.0.38.17   gke-cluster0-pool-d59e9506-vp6t
default       stamps-5b6fc489bc-6xtqz                      2/2       Running        3          16m       10.0.38.13   gke-cluster0-pool-d59e9506-vp6t
default       user-elasticsearch-6b6dd7fc8-b55xx           1/1       Running     0          17m       10.0.38.4    gke-cluster0-pool-d59e9506-vp6t
default       user-http-analytics-6bdd49bd98-p5pd5         1/1       Running     0          10m       10.0.39.8    gke-cluster0-pool-d59e9506-b7nb
default       user-http-graphql-67884c678c-7dcdq           1/1       Running     0          10m       10.0.39.7    gke-cluster0-pool-d59e9506-b7nb
default       user-service-5cbb8cfb4f-t6zhv                1/1       Running     0          10m       10.0.38.15   gke-cluster0-pool-d59e9506-vp6t
default       user-streams-0                               1/1       Running     0          10m       10.0.39.10   gke-cluster0-pool-d59e9506-b7nb
default       user-streams-elasticsearch-c64b64d6f-2nrtl   1/1       Running     3          17m       10.0.38.6    gke-cluster0-pool-d59e9506-vp6t
default       zookeeper-0                                  1/1       Running     0          10m       10.0.39.12   gke-cluster0-pool-d59e9506-b7nb
kube-lego     kube-lego-7799f6b457-skkrc                   1/1       Running     0          17m       10.0.38.5    gke-cluster0-pool-d59e9506-vp6t
kube-system   event-exporter-v0.1.7-7cb7c5d4bf-vr52v       2/2       Running     0          17m       10.0.38.7    gke-cluster0-pool-d59e9506-vp6t
kube-system   fluentd-gcp-v2.0.9-648rh                     2/2       Running     0          20m       10.0.38.2    gke-cluster0-pool-d59e9506-vp6t
kube-system   fluentd-gcp-v2.0.9-8tb4n                     2/2       Running     0          4m        10.0.40.2    gke-cluster0-pool-d59e9506-1rzm
kube-system   fluentd-gcp-v2.0.9-fqjz6                     2/2       Running     0          15m       10.0.39.2    gke-cluster0-pool-d59e9506-b7nb
kube-system   heapster-v1.4.3-6fc45b6cc4-8cl72             3/3       Running     0          11m       10.0.39.6    gke-cluster0-pool-d59e9506-b7nb
kube-system   k8s-snapshots-5699c68696-h8r75               1/1       Running     0          10m       10.0.38.16   gke-cluster0-pool-d59e9506-vp6t
kube-system   kube-dns-778977457c-b48w5                    3/3       Running     0          11m       10.0.39.5    gke-cluster0-pool-d59e9506-b7nb
kube-system   kube-dns-778977457c-sw672                    3/3       Running     0          17m       10.0.38.9    gke-cluster0-pool-d59e9506-vp6t
kube-system   kube-dns-autoscaler-7db47cb9b7-tjt4l         1/1       Running     0          17m       10.0.38.11   gke-cluster0-pool-d59e9506-vp6t
kube-system   kube-proxy-gke-cluster0-pool-d59e9506-1rzm   1/1       Running     0          4m        10.128.0.3   gke-cluster0-pool-d59e9506-1rzm
kube-system   kube-proxy-gke-cluster0-pool-d59e9506-b7nb   1/1       Running     0          15m       10.128.0.4   gke-cluster0-pool-d59e9506-b7nb
kube-system   kube-proxy-gke-cluster0-pool-d59e9506-vp6t   1/1       Running     0          20m       10.128.0.2   gke-cluster0-pool-d59e9506-vp6t
kube-system   kubernetes-dashboard-76c679977c-mwqlv        1/1       Running     0          17m       10.0.38.8    gke-cluster0-pool-d59e9506-vp6t
kube-system   l7-default-backend-6497bcdb4d-wkx28          1/1       Running     0          17m       10.0.38.12   gke-cluster0-pool-d59e9506-vp6t
kube-system   nginx-ingress-controller-78d546664f-gf6mx    1/1       Running     0          11m       10.0.39.3    gke-cluster0-pool-d59e9506-b7nb
kube-system   tiller-deploy-5458cb4cc-26x26                1/1       Running     0          11m       10.0.39.4    gke-cluster0-pool-d59e9506-b7nb

到底是怎么回事？为什么 Pod 没有传播到添加的节点上？我原以为 pod 会分发到第三个节点。我怎样才能让工作负载传播到这个第三个节点？

从技术上讲，就清单资源请求而言，我的整个应用程序适合一个节点。但是当添加第二个节点时，应用程序被分发到第二个节点。所以我认为当我添加第三个节点时，pod 也会被调度到该节点上。但这不是我所看到的。只有DaemonSets 被调度到第三个节点上。我试过扩大和缩小节点池无济于事。

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更新

两个抢占式节点重新启动，现在所有 Pod 都在一个节点上。这是怎么回事？增加资源请求是使它们分散的唯一方法吗？

Answer 1

这是预期的行为。新的 Pod 将被安排到空节点上，但运行中的 Pod 不会自动移动。kubernetes 调度器通常对重新调度 Pod 持保守态度，因此它不会无缘无故地这样做。Pod 可以是有状态的（如 db），因此 kubernetes 不想杀死和重新调度 Pod。

有一个正在开发的项目可以满足您的需求：https : //github.com/kubernetes-incubator/descheduler 我没有使用过它，但它正在社区积极开发中。