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

2019.06.11

欢迎参加在上海举行的贡献者峰会

Author: Josh Berkus (Red Hat)

连续第二年，我们将在 KubeCon China 之前举行一天的 贡献者峰会。 不管您是否已经是一名 Kubernetes 贡献者，还是想要加入社区队伍，贡献一份力量，都请考虑注册参加这次活动。 这次峰会将于六月 24 号，在上海世博中心（和 KubeCon 的举办地点相同）举行， 一天的活动将包含“现有贡献者活动”，以及“新贡献者工作坊”和“文档小组活动”。

现有贡献者活动

去年的贡献者节之后，我们的团队收到了很多反馈意见，很多亚洲和大洋洲的贡献者也想要针对当前贡献者的峰会内容。 有鉴于此，我们在今年的安排中加入了当前贡献者的主题。

尽管我们还没有一个完整的时间安排，下面是当前贡献者主题所会包含的话题：

• 如何撰写 Kubernetes 改进议案 (KEP)
• 代码库研习
• 本地构建以及测试调试
• 不写代码的贡献机会
• SIG-Azure 面对面交流
• SIG-Scheduling 面对面交流
• 其他兴趣小组的面对面机会

整个计划安排将会在完全确定之后，整理放在社区页面上。

如果您的 SIG 想要在 Kubecon Shanghai 上进行面对面的交流，请联系 Josh Berkus。

新贡献者工作坊

参与过去年新贡献者工作坊（NCW）的学生觉得这项活动非常的有价值， 这项活动也帮助、引导了很多亚洲和大洋洲的开发者更多地参与到 Kubernetes 社区之中。

“这次活动可以让人一次快速熟悉社区。”其中的一位参与者提到。

如果您之前从没有参与过 Kubernetes 的贡献，或者只是做过一次或两次贡献，都请考虑注册参加新贡献者工作坊。

“熟悉了从 CLA 到 PR 的整个流程，也认识结交了很多贡献者。”另一位开发者提到。

文档小组活动

文档小组的新老贡献者都会聚首一天，讨论如何提升文档质量，以及将文档翻译成更多的语言。 如果您对翻译文档，将这些知识和信息翻译成中文和其他语言感兴趣的话，请在这里注册，报名参加文档小组活动。

参与之前

不论您参与的是哪一项活动，所有人都需要在到达贡献者峰会前签署 Kubernetes CLA。 您也同时需要考虑带一个合适的笔记本电脑，帮助文档写作或是编程开发。