383 lines
20 KiB
Markdown
383 lines
20 KiB
Markdown
---
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title: "概述"
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description: >
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Kubernetes 是一个可移植、可扩展的开源平台，用于管理容器化的工作负载和服务，方便进行声明式配置和自动化。Kubernetes 拥有一个庞大且快速增长的生态系统，其服务、支持和工具的使用范围广泛。
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content_type: concept
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weight: 20
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card:
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name: concepts
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weight: 10
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anchors:
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- anchor: "#why-you-need-kubernetes-and-what-can-it-do"
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title: 为什么选择 Kubernetes?
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no_list: true
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---
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<!--
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reviewers:
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- bgrant0607
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- mikedanese
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title: "Overview"
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description: >
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Kubernetes is a portable, extensible, open source platform for managing containerized workloads and services, that facilitates both declarative configuration and automation. It has a large, rapidly growing ecosystem. Kubernetes services, support, and tools are widely available.
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content_type: concept
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weight: 20
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card:
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name: concepts
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weight: 10
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anchors:
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- anchor: "#why-you-need-kubernetes-and-what-can-it-do"
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title: Why Kubernetes?
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no_list: true
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-->
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<!-- overview -->
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<!--
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This page is an overview of Kubernetes.
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-->
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此页面是 Kubernetes 的概述。
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<!-- body -->
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<!--
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Kubernetes is a portable, extensible, open source platform for managing containerized
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workloads and services, that facilitates both declarative configuration and automation.
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It has a large, rapidly growing ecosystem. Kubernetes services, support, and tools are widely available.
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-->
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Kubernetes 是一个可移植、可扩展的开源平台，用于管理容器化的工作负载和服务，可促进声明式配置和自动化。
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Kubernetes 拥有一个庞大且快速增长的生态，其服务、支持和工具的使用范围相当广泛。
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<!--
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The name Kubernetes originates from Greek, meaning helmsman or pilot. K8s as an abbreviation
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results from counting the eight letters between the "K" and the "s". Google open-sourced the
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Kubernetes project in 2014. Kubernetes combines
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[over 15 years of Google's experience](/blog/2015/04/borg-predecessor-to-kubernetes/) running
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production workloads at scale with best-of-breed ideas and practices from the community.
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-->
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**Kubernetes** 这个名字源于希腊语，意为“舵手”或“飞行员”。k8s 这个缩写是因为 k 和 s 之间有八个字符的关系。
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Google 在 2014 年开源了 Kubernetes 项目。
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Kubernetes 建立在 [Google 大规模运行生产工作负载十几年经验](https://research.google/pubs/pub43438)的基础上，
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结合了社区中最优秀的想法和实践。
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<!--
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## Going back in time
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Let's take a look at why Kubernetes is so useful by going back in time.
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-->
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## 时光回溯 {#going-back-in-time}
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让我们回顾一下为何 Kubernetes 能够裨益四方。
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<!--
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-->
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<!--
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**Traditional deployment era:**
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Early on, organizations ran applications on physical servers. There was no way to define
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resource boundaries for applications in a physical server, and this caused resource
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allocation issues. For example, if multiple applications run on a physical server, there
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can be instances where one application would take up most of the resources, and as a result,
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the other applications would underperform. A solution for this would be to run each application
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on a different physical server. But this did not scale as resources were underutilized, and it
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was expensive for organizations to maintain many physical servers.
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-->
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**传统部署时代：**
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早期，各个组织是在物理服务器上运行应用程序。
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由于无法限制在物理服务器中运行的应用程序资源使用，因此会导致资源分配问题。
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例如，如果在同一台物理服务器上运行多个应用程序，
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则可能会出现一个应用程序占用大部分资源的情况，而导致其他应用程序的性能下降。
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一种解决方案是将每个应用程序都运行在不同的物理服务器上，
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但是当某个应用程序资源利用率不高时，剩余资源无法被分配给其他应用程序，
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而且维护许多物理服务器的成本很高。
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<!--
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**Virtualized deployment era:** As a solution, virtualization was introduced. It allows you
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to run multiple Virtual Machines (VMs) on a single physical server's CPU. Virtualization
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allows applications to be isolated between VMs and provides a level of security as the
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information of one application cannot be freely accessed by another application.
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-->
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**虚拟化部署时代：**
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因此，虚拟化技术被引入了。虚拟化技术允许你在单个物理服务器的 CPU 上运行多台虚拟机（VM）。
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虚拟化能使应用程序在不同 VM 之间被彼此隔离，且能提供一定程度的安全性，
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因为一个应用程序的信息不能被另一应用程序随意访问。
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<!--
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Virtualization allows better utilization of resources in a physical server and allows
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better scalability because an application can be added or updated easily, reduces
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hardware costs, and much more. With virtualization you can present a set of physical
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resources as a cluster of disposable virtual machines.
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Each VM is a full machine running all the components, including its own operating
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system, on top of the virtualized hardware.
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-->
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虚拟化技术能够更好地利用物理服务器的资源，并且因为可轻松地添加或更新应用程序，
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而因此可以具有更高的可扩缩性，以及降低硬件成本等等的好处。
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通过虚拟化，你可以将一组物理资源呈现为可丢弃的虚拟机集群。
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每个 VM 是一台完整的计算机，在虚拟化硬件之上运行所有组件，包括其自己的操作系统。
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<!--
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**Container deployment era:** Containers are similar to VMs, but they have relaxed
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isolation properties to share the Operating System (OS) among the applications.
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Therefore, containers are considered lightweight. Similar to a VM, a container
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has its own filesystem, share of CPU, memory, process space, and more. As they
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are decoupled from the underlying infrastructure, they are portable across clouds
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and OS distributions.
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-->
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**容器部署时代：**
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容器类似于 VM，但是更宽松的隔离特性，使容器之间可以共享操作系统（OS）。
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因此，容器比起 VM 被认为是更轻量级的。且与 VM 类似，每个容器都具有自己的文件系统、CPU、内存、进程空间等。
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由于它们与基础架构分离，因此可以跨云和 OS 发行版本进行移植。
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<!--
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Containers have become popular because they provide extra benefits, such as:
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-->
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容器因具有许多优势而变得流行起来，例如：
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<!--
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* Agile application creation and deployment: increased ease and efficiency of
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container image creation compared to VM image use.
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* Continuous development, integration, and deployment: provides for reliable
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and frequent container image build and deployment with quick and efficient
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rollbacks (due to image immutability).
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* Dev and Ops separation of concerns: create application container images at
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build/release time rather than deployment time, thereby decoupling
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applications from infrastructure.
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* Observability: not only surfaces OS-level information and metrics, but also
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application health and other signals.
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* Environmental consistency across development, testing, and production: runs
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the same on a laptop as it does in the cloud.
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* Cloud and OS distribution portability: runs on Ubuntu, RHEL, CoreOS, on-premises,
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on major public clouds, and anywhere else.
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* Application-centric management: raises the level of abstraction from running an
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OS on virtual hardware to running an application on an OS using logical resources.
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* Loosely coupled, distributed, elastic, liberated micro-services: applications are
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broken into smaller, independent pieces and can be deployed and managed dynamically –
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not a monolithic stack running on one big single-purpose machine.
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* Resource isolation: predictable application performance.
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* Resource utilization: high efficiency and density.
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-->
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* 敏捷应用程序的创建和部署：与使用 VM 镜像相比，提高了容器镜像创建的简便性和效率。
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* 持续开发、集成和部署：通过快速简单的回滚（由于镜像不可变性），
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提供可靠且频繁的容器镜像构建和部署。
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* 关注开发与运维的分离：在构建、发布时创建应用程序容器镜像，而不是在部署时，
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从而将应用程序与基础架构分离。
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* 可观察性：不仅可以显示 OS 级别的信息和指标，还可以显示应用程序的运行状况和其他指标信号。
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* 跨开发、测试和生产的环境一致性：在笔记本计算机上也可以和在云中运行一样的应用程序。
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* 跨云和操作系统发行版本的可移植性：可在 Ubuntu、RHEL、CoreOS、本地、
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Google Kubernetes Engine 和其他任何地方运行。
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* 以应用程序为中心的管理：提高抽象级别，从在虚拟硬件上运行 OS 到使用逻辑资源在 OS 上运行应用程序。
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* 松散耦合、分布式、弹性、解放的微服务：应用程序被分解成较小的独立部分，
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并且可以动态部署和管理 - 而不是在一台大型单机上整体运行。
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* 资源隔离：可预测的应用程序性能。
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* 资源利用：高效率和高密度。
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<!--
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## Why you need Kubernetes and what it can do {#why-you-need-kubernetes-and-what-can-it-do}
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-->
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## 为什么需要 Kubernetes，它能做什么？ {#why-you-need-kubernetes-and-what-can-it-do}
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<!--
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Containers are a good way to bundle and run your applications. In a production
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environment, you need to manage the containers that run the applications and
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ensure that there is no downtime. For example, if a container goes down, another
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container needs to start. Wouldn't it be easier if this behavior was handled by a system?
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-->
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容器是打包和运行应用程序的好方式。在生产环境中，
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你需要管理运行着应用程序的容器，并确保服务不会下线。
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例如，如果一个容器发生故障，则你需要启动另一个容器。
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如果此行为交由给系统处理，是不是会更容易一些？
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<!--
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That's how Kubernetes comes to the rescue! Kubernetes provides you with a framework
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to run distributed systems resiliently. It takes care of scaling and failover for
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your application, provides deployment patterns, and more. For example: Kubernetes
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can easily manage a canary deployment for your system.
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-->
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这就是 Kubernetes 要来做的事情！
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Kubernetes 为你提供了一个可弹性运行分布式系统的框架。
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Kubernetes 会满足你的扩展要求、故障转移你的应用、提供部署模式等。
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例如，Kubernetes 可以轻松管理系统的 Canary (金丝雀) 部署。
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<!--
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Kubernetes provides you with:
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-->
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Kubernetes 为你提供：
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<!--
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* **Service discovery and load balancing**
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Kubernetes can expose a container using the DNS name or using their own IP address.
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If traffic to a container is high, Kubernetes is able to load balance and distribute
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the network traffic so that the deployment is stable.
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-->
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* **服务发现和负载均衡**
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Kubernetes 可以使用 DNS 名称或自己的 IP 地址来暴露容器。
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如果进入容器的流量很大，
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Kubernetes 可以负载均衡并分配网络流量，从而使部署稳定。
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<!--
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* **Storage orchestration**
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Kubernetes allows you to automatically mount a storage system of your choice, such as
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local storages, public cloud providers, and more.
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-->
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* **存储编排**
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Kubernetes 允许你自动挂载你选择的存储系统，例如本地存储、公共云提供商等。
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<!--
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* **Automated rollouts and rollbacks**
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You can describe the desired state for your deployed containers using Kubernetes,
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and it can change the actual state to the desired state at a controlled rate.
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For example, you can automate Kubernetes to create new containers for your
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deployment, remove existing containers and adopt all their resources to the new container.
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-->
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* **自动部署和回滚**
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你可以使用 Kubernetes 描述已部署容器的所需状态，
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它可以以受控的速率将实际状态更改为期望状态。
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例如，你可以自动化 Kubernetes 来为你的部署创建新容器，
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删除现有容器并将它们的所有资源用于新容器。
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<!--
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* **Automatic bin packing**
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You provide Kubernetes with a cluster of nodes that it can use to run containerized tasks.
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You tell Kubernetes how much CPU and memory (RAM) each container needs. Kubernetes can fit
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containers onto your nodes to make the best use of your resources.
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-->
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* **自动完成装箱计算**
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你为 Kubernetes 提供许多节点组成的集群，在这个集群上运行容器化的任务。
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你告诉 Kubernetes 每个容器需要多少 CPU 和内存 (RAM)。
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Kubernetes 可以将这些容器按实际情况调度到你的节点上，以最佳方式利用你的资源。
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<!--
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* **Self-healing**
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Kubernetes restarts containers that fail, replaces containers, kills containers that don't
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respond to your user-defined health check, and doesn't advertise them to clients until they
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are ready to serve.
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-->
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* **自我修复**
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Kubernetes 将重新启动失败的容器、替换容器、杀死不响应用户定义的运行状况检查的容器，
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并且在准备好服务之前不将其通告给客户端。
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<!--
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* **Secret and configuration management**
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Kubernetes lets you store and manage sensitive information, such as passwords, OAuth tokens,
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and SSH keys. You can deploy and update secrets and application configuration without
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rebuilding your container images, and without exposing secrets in your stack configuration.
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-->
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* **密钥与配置管理**
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Kubernetes 允许你存储和管理敏感信息，例如密码、OAuth 令牌和 SSH 密钥。
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你可以在不重建容器镜像的情况下部署和更新密钥和应用程序配置，也无需在堆栈配置中暴露密钥。
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<!--
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* **Batch execution**
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In addition to services, Kubernetes can manage your batch and CI workloads, replacing containers that fail, if desired.
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* **Horizontal scaling**
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Scale your application up and down with a simple command, with a UI, or automatically based on CPU usage.
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* **IPv4/IPv6 dual-stack**
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Allocation of IPv4 and IPv6 addresses to Pods and Services
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* **Designed for extensibility**
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Add features to your Kubernetes cluster without changing upstream source code.
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-->
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* **批处理执行**
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除了服务外，Kubernetes 还可以管理你的批处理和 CI（持续集成）工作负载，如有需要，可以替换失败的容器。
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* **水平扩缩**
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使用简单的命令、用户界面或根据 CPU 使用率自动对你的应用进行扩缩。
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* **IPv4/IPv6 双栈**
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为 Pod（容器组）和 Service（服务）分配 IPv4 和 IPv6 地址。
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* **为可扩展性设计**
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在不改变上游源代码的情况下为你的 Kubernetes 集群添加功能。
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<!--
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## What Kubernetes is not
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-->
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## Kubernetes 不是什么 {#what-kubernetes-is-not}
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<!--
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Kubernetes is not a traditional, all-inclusive PaaS (Platform as a Service) system.
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Since Kubernetes operates at the container level rather than at the hardware level,
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it provides some generally applicable features common to PaaS offerings, such as
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deployment, scaling, load balancing, and lets users integrate their logging, monitoring,
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and alerting solutions. However, Kubernetes is not monolithic, and these default solutions
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are optional and pluggable. Kubernetes provides the building blocks for building developer
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platforms, but preserves user choice and flexibility where it is important.
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-->
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Kubernetes 不是传统的、包罗万象的 PaaS（平台即服务）系统。
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由于 Kubernetes 是在容器级别运行，而非在硬件级别，它提供了 PaaS 产品共有的一些普遍适用的功能，
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例如部署、扩展、负载均衡，允许用户集成他们的日志记录、监控和警报方案。
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但是，Kubernetes 不是单体式（monolithic）系统，那些默认解决方案都是可选、可插拔的。
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Kubernetes 为构建开发人员平台提供了基础，但是在重要的地方保留了用户选择权，能有更高的灵活性。
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|
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<!--
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Kubernetes:
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-->
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Kubernetes：
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<!--
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* Does not limit the types of applications supported. Kubernetes aims to support an
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extremely diverse variety of workloads, including stateless, stateful, and data-processing
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workloads. If an application can run in a container, it should run great on Kubernetes.
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* Does not deploy source code and does not build your application. Continuous Integration,
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Delivery, and Deployment (CI/CD) workflows are determined by organization cultures and
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preferences as well as technical requirements.
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* Does not provide application-level services, such as middleware (for example, message buses),
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data-processing frameworks (for example, Spark), databases (for example, MySQL), caches, nor
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cluster storage systems (for example, Ceph) as built-in services. Such components can run on
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Kubernetes, and/or can be accessed by applications running on Kubernetes through portable
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mechanisms, such as the [Open Service Broker](https://openservicebrokerapi.org/).
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-->
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* 不限制支持的应用程序类型。
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Kubernetes 旨在支持极其多种多样的工作负载，包括无状态、有状态和数据处理工作负载。
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如果应用程序可以在容器中运行，那么它应该可以在 Kubernetes 上很好地运行。
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* 不部署源代码，也不构建你的应用程序。
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持续集成（CI）、交付和部署（CI/CD）工作流取决于组织的文化和偏好以及技术要求。
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* 不提供应用程序级别的服务作为内置服务，例如中间件（例如消息中间件）、
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数据处理框架（例如 Spark）、数据库（例如 MySQL）、缓存、集群存储系统
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（例如 Ceph）。这样的组件可以在 Kubernetes 上运行，并且/或者可以由运行在
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Kubernetes 上的应用程序通过可移植机制（例如[开放服务代理](https://openservicebrokerapi.org/)）来访问。
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<!--
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||
* Does not dictate logging, monitoring, or alerting solutions. It provides some integrations
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as proof of concept, and mechanisms to collect and export metrics.
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* Does not provide nor mandate a configuration language/system (for example, Jsonnet). It provides
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a declarative API that may be targeted by arbitrary forms of declarative specifications.
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* Does not provide nor adopt any comprehensive machine configuration, maintenance, management,
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or self-healing systems.
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* Additionally, Kubernetes is not a mere orchestration system. In fact, it eliminates the need
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for orchestration. The technical definition of orchestration is execution of a defined workflow:
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first do A, then B, then C. In contrast, Kubernetes comprises a set of independent, composable
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||
control processes that continuously drive the current state towards the provided desired state.
|
||
It shouldn't matter how you get from A to C. Centralized control is also not required. This
|
||
results in a system that is easier to use and more powerful, robust, resilient, and extensible.
|
||
-->
|
||
* 不是日志记录、监视或警报的解决方案。
|
||
它集成了一些功能作为概念证明，并提供了收集和导出指标的机制。
|
||
* 不提供也不要求配置用的语言、系统（例如 jsonnet），它提供了声明性 API，
|
||
该声明性 API 可以由任意形式的声明性规范所构成。
|
||
* 不提供也不采用任何全面的机器配置、维护、管理或自我修复系统。
|
||
* 此外，Kubernetes 不仅仅是一个编排系统，实际上它消除了编排的需要。
|
||
编排的技术定义是执行已定义的工作流程：首先执行 A，然后执行 B，再执行 C。
|
||
而 Kubernetes 包含了一组独立可组合的控制过程，可以持续地将当前状态驱动到所提供的预期状态。
|
||
你不需要在乎如何从 A 移动到 C，也不需要集中控制，这使得系统更易于使用且功能更强大、
|
||
系统更健壮，更为弹性和可扩展。
|
||
|
||
## {{% heading "whatsnext" %}}
|
||
|
||
<!--
|
||
* Take a look at the [Kubernetes Components](/docs/concepts/overview/components/)
|
||
* Take a look at the [The Kubernetes API](/docs/concepts/overview/kubernetes-api/)
|
||
* Take a look at the [Cluster Architecture](/docs/concepts/architecture/)
|
||
* Ready to [Get Started](/docs/setup/)?
|
||
-->
|
||
* 查阅 [Kubernetes 组件](/zh-cn/docs/concepts/overview/components/)
|
||
* 查阅 [Kubernetes API](/zh-cn/docs/concepts/overview/kubernetes-api/)
|
||
* 查阅 [Cluster 架构](/zh-cn/docs/concepts/architecture/)
|
||
* 开始 [Kubernetes 的建置](/zh-cn/docs/setup/)吧！
|