zh-trans content/en/blog/_posts/2019-11-26-cloud-native-java-controller-sdk.md (#18526)
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Kubernetes Prow Robot
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layout: blog
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title: "使用 Java 开发一个 Kubernetes controller"
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date: 2019-11-26
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slug: Develop-A-Kubernetes-Controller-in-Java
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---
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<!--
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---
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layout: blog
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title: "Develop a Kubernetes controller in Java"
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date: 2019-11-26
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slug: Develop-A-Kubernetes-Controller-in-Java
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---
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-->
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<!--
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**Authors:** Min Kim (Ant Financial), Tony Ado (Ant Financial)
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-->
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**作者:** Min Kim (蚂蚁金服), Tony Ado (蚂蚁金服)
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<!--
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The official [Kubernetes Java SDK](https://github.com/kubernetes-client/java) project
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recently released their latest work on providing the Java Kubernetes developers
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a handy Kubernetes controller-builder SDK which is helpful for easily developing
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advanced workloads or systems.
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-->
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[Kubernetes Java SDK](https://github.com/kubernetes-client/java) 官方项目最近发布了他们的最新工作，为 Java Kubernetes 开发人员提供一个便捷的 Kubernetes 控制器-构建器 SDK，它有助于轻松开发高级工作负载或系统。
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<!--
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## Overall
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Java is no doubt one of the most popular programming languages in the world but
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it's been difficult for a period time for those non-Golang developers to build up
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their customized controller/operator due to the lack of library resources in the
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community. In the world of Golang, there're already some excellent controller
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frameworks, for example, [controller runtime](https://github.com/kubernetes-sigs/controller-runtime),
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[operator SDK](https://github.com/operator-framework/operator-sdk). These
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existing Golang frameworks are relying on the various utilities from the
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[Kubernetes Golang SDK](https://github.com/kubernetes/client-go) proven to
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be stable over years. Driven by the emerging need of further integration into
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the platform of Kubernetes, we not only ported many essential toolings from the Golang
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SDK into the kubernetes Java SDK including informers, work-queues, leader-elections,
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etc. but also developed a controller-builder SDK which wires up everything into
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a runnable controller without hiccups.
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-->
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## 综述
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Java 无疑是世界上最流行的编程语言之一，但由于社区中缺少库资源，一段时间以来，那些非 Golang 开发人员很难构建他们定制的 controller/operator。在 Golang 的世界里，已经有一些很好的 controller 框架了，例如，[controller runtime](https://github.com/kubernetes-sigs/controller-runtime)，[operator SDK](https://github.com/operator-framework/operator-sdk)。这些现有的 Golang 框架依赖于 [Kubernetes Golang SDK](https://github.com/kubernetes/client-go) 提供的各种实用工具，这些工具经过多年证明是稳定的。受进一步集成到 Kubernetes 平台的需求驱动，我们不仅将 Golang SDK 中的许多基本工具移植到 kubernetes Java SDK 中，包括 informers、work-queues、leader-elections 等，也开发了一个控制器构建 SDK，它可以将所有东西连接到一个可运行的控制器中，而不会产生任何问题。
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<!--
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## Backgrounds
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Why use Java to implement Kubernetes tooling? You might pick Java for:
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- __Integrating legacy enterprise Java systems__: Many companies have their legacy
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systems or frameworks written in Java in favor of stability. We are not able to
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move everything to Golang easily.
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- __More open-source community resources__: Java is mature and has accumulated abundant open-source
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libraries over decades, even though Golang is getting more and more fancy and
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popular for developers. Additionally, nowadays developers are able to develop
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their aggregated-apiservers over SQL-storage and Java has way better support on SQLs.
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-->
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## 背景
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为什么要使用 Java 实现 kubernetes 工具？选择 Java 的原因可能是：
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- __集成遗留的企业级 Java 系统__：许多公司的遗留系统或框架都是用 Java 编写的，用以支持稳定性。我们不能轻易把所有东西搬到 Golang。
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- __更多开源社区的资源__：Java 是成熟的，并且在过去几十年中累计了丰富的开源库，尽管 Golang 对于开发人员来说越来越具有吸引力，越来越流行。此外，现在开发人员能够在 SQL 存储上开发他们的聚合-apiserver，而 Java 在 SQL 上有更好的支持。
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<!--
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## How to use?
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Take maven project as example, adding the following dependencies into your dependencies:
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-->
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## 如何去使用
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以 maven 项目为例，将以下依赖项添加到您的依赖中：
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```xml
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<dependency>
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<groupId>io.kubernetes</groupId>
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<artifactId>client-java-extended</artifactId>
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<version>6.0.1</version>
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</dependency>
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```
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<!--
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Then we can make use of the provided builder libraries to write your own controller.
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For example, the following one is a simple controller prints out node information
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on watch notification, see complete example [here](https://github.com/kubernetes-client/java/blob/master/examples/src/main/java/io/kubernetes/client/examples/ControllerExample.java):
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-->
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然后我们可以使用提供的生成器库来编写自己的控制器。例如，下面是一个简单的控制，它打印出关于监视通知的节点信息，请看完整的例子：
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```java
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...
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Reconciler reconciler = new Reconciler() {
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@Override
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public Result reconcile(Request request) {
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V1Node node = nodeLister.get(request.getName());
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System.out.println("triggered reconciling " + node.getMetadata().getName());
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return new Result(false);
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}
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};
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Controller controller =
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ControllerBuilder.defaultBuilder(informerFactory)
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.watch(
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(workQueue) -> ControllerBuilder.controllerWatchBuilder(V1Node.class, workQueue).build())
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.withReconciler(nodeReconciler) // required, set the actual reconciler
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.withName("node-printing-controller") // optional, set name for controller for logging, thread-tracing
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.withWorkerCount(4) // optional, set worker thread count
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.withReadyFunc( nodeInformer::hasSynced) // optional, only starts controller when the cache has synced up
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.build();
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```
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<!--
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If you notice, the new Java controller framework learnt a lot from the design of
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[controller-runtime](https://github.com/kubernetes-sigs/controller-runtime) which
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successfully encapsulates the complex components inside controller into several
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clean interfaces. With the help of Java Generics, we even move on a bit and simply
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the encapsulation in a better way.
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-->
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如果您留意，新的 Java 控制器框架很多地方借鉴于 [controller-runtime](https://github.com/kubernetes-sigs/controller-runtime) 的设计，它成功地将控制器内部的复杂组件封装到几个干净的接口中。在 Java 泛型的帮助下，我们甚至更进一步，以更好的方式简化了封装。
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<!--
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As for more advanced usage, we can wrap multiple controllers into a controller-manager
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or a leader-electing controller which helps deploying in HA setup. In a word, we can
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basically find most of the equivalence implementations here from Golang SDK and
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more advanced features are under active development by us.
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-->
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我们可以将多个控制器封装到一个 controller-manager 或 leader-electing controller 中，这有助于在 HA 设置中进行部署。
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<!--
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## Future steps
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The community behind the official Kubernetes Java SDK project will be focusing on
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providing more useful utilities for developers who hope to program cloud native
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Java applications to extend Kubernetes. If you are interested in more details,
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please look at our repo [kubernetes-client/java](https://github.com/kubernetes-client/java).
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Feel free to share also your feedback with us, through Issues or [Slack](http://kubernetes.slack.com/messages/kubernetes-client/).
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-->
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## 未来计划
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Kubernetes Java SDK 项目背后的社区将专注于为希望编写云原生 Java 应用程序来扩展 Kubernetes 的开发人员提供更有用的实用程序。如果您对更详细的信息感兴趣，请查看我们的仓库 [kubernetes-client/java](https://github.com/kubernetes-client/java)。请通过问题或 [Slack](http://kubernetes.slack.com/messages/kubernetes-client/) 与我们分享您的反馈。
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