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K8S综述Return Parent

  • Kubernetes版本

    • 版本号：

    Kubernetes 版本号格式为 x.y.z，其中 x 为大版本号，y 为小版本号，z 为补丁版本号。版本号格式遵循 Semantic Versioning 规则。

    x大版本号: when you make incompatible API changes,

    y小版本号: when you add functionality in a backwards compatible manner,

    z补丁版本号： when you make backwards compatible bug fixes.

    • 各组件间协作对版本的要求

    kubelet： 版本号不能高于 kube-apiserver，最多可以比 kube-apiserver 低两个小版本。

    在 可用（HA）集群中， 多个 kube-apiserver 实例小版本号最多差1。

    kube-controller-manager、kube-scheduler 和 cloud-controller-manager 版本不能高于 kube-apiserver 版本号。最好它们的版本号与 kube-apiserver 保持一致，但允许比 kube-apiserver 低一个小版本。

    kubectl 可以比 kube-apiserver 高一个小版本，也可以低一个小版本。

    kubernetes版本发布计划见：https://github.com/kubernetes/sig-release/blob/master/releases/patch-releases.md

  • kubernetes可以支持对象的体量

    在 v1.21 版本中， Kubernetes 支持的最大节点数为 5000。具体的来说，v1.21 版本可以支持如下体量的对象：

    • 节点数不超过 5000
    • Pod 总数不超过 150000
    • 容器总数不超过 300000
    • 每个节点的 pod 数量不超过 100

  • kubernetes支持的容器运行时

    在Linux平台上， Kubernetes支持以下三种容器运行时：

    containerd: https://github.com/containerd/containerd

    CRI-O: https://github.com/cri-o/cri-o 由redhat,IBM等公司主导开发

    Docker: https://github.com/moby/moby

    Docker、CRI-O、containerd和runc之间的关系如下图所示：

    ![Diagram showing the relationships and dependencies between docker, Kubernetes, CRI-O, containerd and runc]avatar

  • K8S组件功能的状态

    A feature can be in Alpha, Beta or GA stage. An Alpha feature means:

    Alpha:

    • Disabled by default
    • Might be buggy. Enabling the feature may expose bugs.
    • Support for feature may be dropped at any time without notice.
    • The API may change in incompatible ways in a later software release without notice.
    • Recommended for use only in short-lived testing clusters, due to increased risk of bugs and lack of long-term support.

    Beta：

    • Enabled by default.
    • The feature is well tested. Enabling the feature is considered safe.
    • Support for the overall feature will not be dropped, though details may change.
    • The schema and/or semantics of objects may change in incompatible ways in a subsequent beta or stable release. When this happens, we will provide instructions for migrating to the next version. This may require deleting, editing, and re-creating API objects. The editing process may require some thought. This may require downtime for applications that rely on the feature.
    • Recommended for only non-business-critical uses because of potential for incompatible changes in subsequent releases. If you have multiple clusters that can be upgraded independently, you may be able to relax this restriction.

    GA(General Availability):

    A General Availability (GA) feature is also referred to as a stable feature

    • The feature is always enabled; you cannot disable it.
    • The corresponding feature gate is no longer needed.
    • Stable versions of features will appear in released software for many subsequent versions.

    Note: feature current stages of K8S ,look at: https://kubernetes.io/docs/reference/command-line-tools-reference/feature-gates/#feature-stages