Wednesday, September 18, 2019
Kubernetes 1.16: Custom Resources, Overhauled Metrics, and Volume Extensions
Authors: Kubernetes 1.16 Release Team
We’re pleased to announce the delivery of Kubernetes 1.16, our third release of 2019! Kubernetes 1.16 consists of 31 enhancements: 8 enhancements moving to stable, 8 enhancements in beta, and 15 enhancements in alpha.
Major Themes
Custom resources
CRDs are in widespread use as a Kubernetes extensibility mechanism and have been available in beta since the 1.7 release. The 1.16 release marks the graduation of CRDs to general availability (GA).
Overhauled metrics
Kubernetes has previously made extensive use of a global metrics registry to register metrics to be exposed. By implementing a metrics registry, metrics are registered in more transparent means. Previously, Kubernetes metrics have been excluded from any kind of stability requirements.
Volume Extension
There are quite a few enhancements in this release that pertain to volumes and volume modifications. Volume resizing support in CSI specs is moving to beta which allows for any CSI spec volume plugin to be resizable.
Additional Enhancements
Custom Resources Reach General Availability
CRDs have become the basis for extensions in the Kubernetes ecosystem. Started as a ground-up redesign of the ThirdPartyResources prototype, they have finally reached GA in 1.16 with apiextensions.k8s.io/v1, as the hard-won lessons of API evolution in Kubernetes have been integrated. As we transition to GA, the focus is on data consistency for API clients.
As you upgrade to the GA API, you’ll notice that several of the previously optional guard rails have become required and/or default behavior. Things like structural schemas, pruning unknown fields, validation, and protecting the *.k8s.io group are important for ensuring the longevity of your APIs and are now much harder to accidentally miss. Defaulting is another important part of API evolution and that support will be on by default for CRD.v1. The combination of these, along with CRD conversion mechanisms are enough to build stable APIs that evolve over time, the same way that native Kubernetes resources have changed without breaking backward-compatibility.
Updates to the CRD API won’t end here. We have ideas for features like arbitrary subresources, API group migration, and maybe a more efficient serialization protocol, but the changes from here are expected to be optional and complementary in nature to what’s already here in the GA API. Happy operator writing!
Details on how to work with custom resources can be found in the Kubernetes documentation.
Opening Doors With Windows Enhancements
Beta: Enhancing the workload identity options for Windows containers
Active Directory Group Managed Service Account (GMSA) support is graduating to beta and certain annotations that were introduced with the alpha support are being deprecated. GMSA is a specific type of Active Directory account that enables Windows containers to carry an identity across the network and communicate with other resources. Windows containers can now gain authenticated access to external resources. In addition, GMSA provides automatic password management, simplified service principal name (SPN) management, and the ability to delegate the management to other administrators across multiple servers.
Adding support for RunAsUserName as an alpha release. The RunAsUserName is a string specifying the windows identity (or username) in Windows to run the entrypoint of the container and is a part of the newly introduced windowsOptions component of the securityContext (WindowsSecurityContextOptions).
Alpha: Improvements to setup & node join experience with kubeadm
Introducing alpha support for kubeadm, enabling Kubernetes users to easily join (and reset) Windows worker nodes to an existing cluster the same way they do for Linux nodes. Users can utilize kubeadm to prepare and add a Windows node to cluster. When the operations are complete, the node will be in a Ready state and able to run Windows containers. In addition, we will also provide a set of Windows-specific scripts to enable the installation of prerequisites and CNIs ahead of joining the node to the cluster.
Alpha: Introducing support for Container Storage Interface (CSI)
Introducing CSI plugin support for out-of-tree providers, enabling Windows nodes in a Kubernetes cluster to leverage persistent storage capabilities for Windows-based workloads. This significantly expands the storage options of Windows workloads, adding onto a list that included FlexVolume and in-tree storage plugins. This capability is achieved through a host OS proxy that enables the execution of privileged operations on the Windows node on behalf of containers.
Introducing Endpoint Slices
The release of Kubernetes 1.16 includes an exciting new alpha feature: Endpoint Slices. These provide a scalable and extensible alternative to Endpoints resources. Behind the scenes, these resources play a big role in network routing within Kubernetes. Each network endpoint is tracked within these resources, and kube-proxy uses them for generating proxy rules that allow pods to communicate with each other so easily in Kubernetes.
Providing Greater Scalability
A key goal for Endpoint Slices is to enable greater scalability for Kubernetes Services. With the existing Endpoints resources, a single resource must include network endpoints representing all pods matching a Service. As Services start to scale to thousands of pods, the corresponding Endpoints resources become quite large. Simply adding or removing one endpoint from a Service at this scale can be quite costly. As the Endpoints resource is updated, every piece of code watching Endpoints will need to be sent a full copy of the resource. With kube-proxy running on every node in a cluster, a copy needs to be sent to every single node. At a small scale, this is not an issue, but it becomes increasingly noticeable as clusters get larger.
As a simple example, in a cluster with 5,000 nodes and a 1MB Endpoints object, any update would result in approximately 5GB transmitted (that’s enough to fill a DVD). This becomes increasingly significant given how frequently Endpoints can change during events like rolling updates on Deployments.
With Endpoint Slices, network endpoints for a Service are split into multiple resources, significantly decreasing the amount of data required for updates at scale. By default, Endpoint Slices are limited to 100 endpoints each.
For example, let’s take a cluster with 20,000 network endpoints spread over 5,000 nodes. Updating a single endpoint will be much more efficient with Endpoint Slices since each one includes only a tiny portion of the total number of network endpoints. Instead of transferring a big Endpoints object to each node, only the small Endpoint Slice that’s been changed has to be transferred. The net effect is that approximately 200x less data needs to be transferred for this update.
| Endpoints | Endpoint Slices | |
| # of resources | 1 | 20k / 100 = 200 |
| # of network endpoints stored | 1 * 20k = 20k | 200 * 100 = 20k |
| size of each resource | 20k * const = ~2.0 MB | 100 * const = ~10 kB |
| watch event data transferred | ~2.0MB * 5k = 10GB | ~10kB * 5k = 50MB |
The second primary goal for Endpoint Slices was to provide a resource that would be highly extensible and useful across a wide variety of use cases. One of the key additions with Endpoint Slices involves a new topology attribute. By default, this will be populated with the existing topology labels used throughout Kubernetes indicating attributes such as region and zone. Of course, this field can be populated with custom labels as well for more specialized use cases.
Endpoint Slices also include greater flexibility for address types. Each contains a list of addresses. An initial use case for multiple addresses would be to support dual stack endpoints with both IPv4 and IPv6 addresses.
The Kubernetes documentation has a lot more information about Endpoint Slices. There’s also a great KubeCon talk that provides more information on the initial rationale for developing Endpoint Slices. As an alpha feature in Kubernetes 1.16, they will not be enabled by default, but the docs cover how to enable them in your cluster.
Notable Feature Updates
- Topology Manager, a new Kubelet component, aims to co-ordinate resource assignment decisions to provide optimized resource allocations.
- IPv4/IPv6 dual-stack enables the allocation of both IPv4 and IPv6 addresses to Pods and Services.
- Extensions for Cloud Controller Manager Migration.
- Continued deprecation of extensions/v1beta1, apps/v1beta1, and apps/v1beta2 APIs. These extensions are now retired in 1.16!
Availability
Kubernetes 1.16 is available for download on GitHub. To get started with Kubernetes, check out these interactive tutorials. You can also easily install 1.16 using kubeadm.
Release Team
This release is made possible through the efforts of hundreds of individuals who contributed both technical and non-technical content. Special thanks to the release team led by Lachlan Evenson, Principal Program Manager at Microsoft. The 32 individuals on the release team coordinated many aspects of the release, from documentation to testing, validation, and feature completeness.
As the Kubernetes community has grown, our release process represents an amazing demonstration of collaboration in open source software development. Kubernetes continues to gain new users at a rapid pace. This growth creates a positive feedback cycle where more contributors commit code creating a more vibrant ecosystem. Kubernetes has had over 32,000 individual contributors to date and an active community of more than 66,000 people.
Release Mascot
The Kubernetes 1.16 release crest was loosely inspired by the Apollo 16 mission crest. It represents the hard work of the release-team and the community alike and is an ode to the challenges and fun times we shared as a team throughout the release cycle. Many thanks to Ronan Flynn-Curran of Microsoft for creating this magnificent piece.
Kubernetes Updates
Project Velocity
The CNCF has continued refining DevStats, an ambitious project to visualize the myriad contributions that go into the project. K8s DevStats illustrates the breakdown of contributions from major company contributors, as well as an impressive set of preconfigured reports on everything from individual contributors to pull request lifecycle times. This past year, 1,147 different companies and over 3,149 individuals contribute to Kubernetes each month. Check out DevStats to learn more about the overall velocity of the Kubernetes project and community.
Ecosystem
- The Kubernetes project leadership created the Security Audit Working Group to oversee the very first third-part Kubernetes security audit, in an effort to improve the overall security of the ecosystem.
- The Kubernetes Certified Service Providers program (KCSP) reached 100 member companies, ranging from the largest multinational cloud, enterprise software, and consulting companies to tiny startups.
- The first Kubernetes Project Journey Report was released, showcasing the massive growth of the project.
KubeCon + CloudNativeCon
The Cloud Native Computing Foundation’s flagship conference gathers adopters and technologists from leading open source and cloud native communities in San Diego, California from November 18-21, 2019. Join Kubernetes, Prometheus, Envoy, CoreDNS, containerd, Fluentd, OpenTracing, gRPC, CNI, Jaeger, Notary, TUF, Vitess, NATS, Linkerd, Helm, Rook, Harbor, etcd, Open Policy Agent, CRI-O, and TiKV as the community gathers for four days to further the education and advancement of cloud native computing. Register today!
Webinar
Join members of the Kubernetes 1.16 release team on Oct 22, 2019 to learn about the major features in this release. Register here.
Get Involved
The simplest way to get involved with Kubernetes is by joining one of the many Special Interest Groups (SIGs) that align with your interests. Have something you’d like to broadcast to the Kubernetes community? Share your voice at our weekly community meeting, and through the channels below. Thank you for your continued feedback and support.
- Follow us on Twitter @Kubernetesio for latest updates
- Join the community discussion on Discuss
- Join the community on Slack
- Post questions (or answer questions) on Stack Overflow
- Share your Kubernetes story
2019.04.26
如何参与 Kubernetes 文档的本地化工作
作者: Zach Corleissen（Linux 基金会）
去年我们对 Kubernetes 网站进行了优化，加入了多语言内容的支持。贡献者们踊跃响应，加入了多种新的本地化内容：截至 2019 年 4 月，Kubernetes 文档有了 9 个不同语言的未完成版本，其中有 6 个是 2019 年加入的。在每个 Kubernetes 文档页面的上方，读者都可以看到一个语言选择器，其中列出了所有可用语言。
不论是完成度最高的中文版 v1.12，还是最新加入的葡萄牙文版 v1.14，各语言的本地化内容还未完成，这是一个进行中的项目。如果读者有兴趣对现有本地化工作提供支持，请继续阅读。
什么是本地化
翻译是以词表意的问题。而本地化在此基础之上，还包含了过程和设计方面的工作。
本地化和翻译很像，但是包含更多内容。除了进行翻译之外，本地化还要为编写和发布过程的框架进行优化。例如，Kubernetes.io 多数的站点浏览功能（按钮文字）都保存在单独的文件之中。所以启动新本地化的过程中，需要包含加入对特定文件中字符串进行翻译的工作。
本地化很重要，能够有效的降低 Kubernetes 的采纳和支持门槛。如果能用母语阅读 Kubernetes 文档，就能更轻松的开始使用 Kubernetes，并对其发展作出贡献。
如何启动本地化工作
不同语言的本地化工作都是单独的功能——和其它 Kubernetes 功能一致，贡献者们在一个 SIG 中进行本地化工作，分享出来进行评审，并加入项目。
贡献者们在团队中进行内容的本地化工作。因为自己不能批准自己的 PR，所以一个本地化团队至少应该有两个人——例如意大利文的本地化团队有两个人。这个团队规模可能很大：中文团队有几十个成员。
每个团队都有自己的工作流。有些团队手工完成所有的内容翻译；有些会使用带有翻译插件的编译器，并使用评审机来提供正确性的保障。SIG Docs 专注于输出的标准；这就给了本地化团队采用适合自己工作情况的工作流。这样一来，团队可以根据最佳实践进行协作，并以 Kubernetes 的社区精神进行分享。
为本地化工作添砖加瓦
如果你有兴趣为 Kubernetes 文档加入新语种的本地化内容，Kubernetes contribution guide 中包含了这方面的相关内容。
已经启动的的本地化工作同样需要支持。如果有兴趣为现存项目做出贡献，可以加入本地化团队的 Slack 频道，去做个自我介绍。各团队的成员会帮助你开始工作。
| 语种 | Slack 频道 |
|---|---|
| 中文 | #kubernetes-docs-zh |
| 英文 | #sig-docs |
| 法文 | #kubernetes-docs-fr |
| 德文 | #kubernetes-docs-de |
| 印地 | #kubernetes-docs-hi |
| 印度尼西亚文 | #kubernetes-docs-id |
| 意大利文 | #kubernetes-docs-it |
| 日文 | #kubernetes-docs-ja |
| 韩文 | #kubernetes-docs-ko |
| 葡萄牙文 | #kubernetes-docs-pt |
| 西班牙文 | #kubernetes-docs-es |
下一步？
最新的印地文本地化工作正在启动。为什么不加入你的语言？
身为 SIG Docs 的主席，我甚至希望本地化工作跳出文档范畴，直接为 Kubernetes 组件提供本地化支持。有什么组件是你希望支持不同语言的么？可以提交一个 Kubernetes Enhancement Proposal 来促成这一进步。