Merge pull request #39653 from wzshiming/blog/introducing-kwok

Blog post introducing kwok

Author: k8s-ci-robot

content/en/blog/_posts/2023-03-01-introducing-kwok/index.md

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+---
+layout: blog
+title: "Introducing KWOK: Kubernetes WithOut Kubelet"
+date: 2023-03-01
+slug: introducing-kwok
+canonicalUrl: https://kubernetes.dev/blog/2023/03/01/introducing-kwok/
+---
+
+**Author:** Shiming Zhang (DaoCloud), Wei Huang (Apple), Yibo Zhuang (Apple)
+
+<img style="float: right; display: inline-block; margin-left: 2em; max-width: 15em;" src="/blog/2023/03/01/introducing-kwok/kwok.svg" alt="KWOK logo" />
+
+Have you ever wondered how to set up a cluster of thousands of nodes just in seconds, how to simulate real nodes with a low resource footprint, and how to test your Kubernetes controller at scale without spending much on infrastructure?
+
+If you answered "yes" to any of these questions, then you might be interested in KWOK, a toolkit that enables you to create a cluster of thousands of nodes in seconds.
+
+## What is KWOK?
+
+KWOK stands for Kubernetes WithOut Kubelet. So far, it provides two tools:
+
+`kwok`
+: `kwok` is the cornerstone of this project, responsible for simulating the lifecycle of fake nodes, pods, and other Kubernetes API resources.
+
+`kwokctl`
+: `kwokctl` is a CLI tool designed to streamline the creation and management of clusters, with nodes simulated by `kwok`.
+
+## Why use KWOK?
+
+KWOK has several advantages:
+
+- **Speed**: You can create and delete clusters and nodes almost instantly, without waiting for boot or provisioning.
+- **Compatibility**: KWOK works with any tools or clients that are compliant with Kubernetes APIs, such as kubectl, helm, kui, etc.
+- **Portability**: KWOK has no specific hardware or software requirements. You can run it using pre-built images, once Docker or Nerdctl is installed. Alternatively, binaries are also available for all platforms and can be easily installed.
+- **Flexibility**: You can configure different node types, labels, taints, capacities, conditions, etc., and you can configure different pod behaviors, status, etc. to test different scenarios and edge cases.
+- **Performance**: You can simulate thousands of nodes on your laptop without significant consumption of CPU or memory resources.
+
+## What are the use cases?
+
+KWOK can be used for various purposes:
+
+- **Learning**: You can use KWOK to learn about Kubernetes concepts and features without worrying about resource waste or other consequences. 
+- **Development**: You can use KWOK to develop new features or tools for Kubernetes without accessing to a real cluster or requiring other components.
+- **Testing**:
+  - You can measure how well your application or controller scales with different numbers of nodes and(or) pods.
+  - You can generate high loads on your cluster by creating many pods or services with different resource requests or limits.
+  - You can simulate node failures or network partitions by changing node conditions or randomly deleting nodes.
+  - You can test how your controller interacts with other components or features of Kubernetes by enabling different feature gates or API versions.
+
+## What are the limitations?
+
+KWOK is not intended to replace others completely. It has some limitations that you should be aware of:
+
+- **Functionality**: KWOK is not a kubelet and may exhibit different behaviors in areas such as pod lifecycle management, volume mounting, and device plugins. Its primary function is to simulate updates of node and pod status.
+- **Accuracy**: It's important to note that KWOK doesn't accurately reflect the performance or behavior of real nodes under various workloads or environments. Instead, it approximates some behaviors using simple formulas.
+- **Security**: KWOK does not enforce any security policies or mechanisms on simulated nodes. It assumes that all requests from the kube-apiserver are authorized and valid.
+
+## Getting started
+
+If you are interested in trying out KWOK, please check its [documents] for more details.
+
+{{< figure src="/blog/2023/03/01/introducing-kwok/manage-clusters.svg" alt="Animation of a terminal showing kwokctl in use" caption="Using kwokctl to manage simulated clusters" >}}
+
+## Getting Involved
+
+If you're interested in participating in future discussions or development related to KWOK, there are several ways to get involved:
+
+- Slack: [#kwok] for general usage discussion, [#kwok-dev] for development discussion. (visit [slack.k8s.io] for a workspace invitation)
+- Open Issues/PRs/Discussions in [sigs.k8s.io/kwok]
+
+We welcome feedback and contributions from anyone who wants to join us in this exciting project.
+
+[documents]: https://kwok.sigs.k8s.io/
+[sigs.k8s.io/kwok]: https://sigs.k8s.io/kwok/
+[#kwok]: https://kubernetes.slack.com/messages/kwok/
+[#kwok-dev]: https://kubernetes.slack.com/messages/kwok-dev/
+[slack.k8s.io]: https://slack.k8s.io/