[zh-cn] translate 2024-08-15-consistent-read-from-cache.md

Co-authored-by: Qiming Teng <tengqm@outlook.com>

content/zh-cn/blog/_posts/2024-08-15-consistent-read-from-cache.md

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+---
+layout: blog
+title: 'Kubernetes v1.31：通过基于缓存的一致性读加速集群性能'
+date: 2024-08-15
+slug: consistent-read-from-cache-beta
+author: >
+  Marek Siarkowicz (Google)
+translator: >
+  [Jin Li](https://github.com/qlijin) (UOS)
+---
+<!--
+layout: blog
+title: 'Kubernetes v1.31: Accelerating Cluster Performance with Consistent Reads from Cache'
+date: 2024-08-15
+slug: consistent-read-from-cache-beta
+author: >
+  Marek Siarkowicz (Google)
+->
+
+<!--
+Kubernetes is renowned for its robust orchestration of containerized applications,
+but as clusters grow, the demands on the control plane can become a bottleneck.
+A key challenge has been ensuring strongly consistent reads from the etcd datastore,
+requiring resource-intensive quorum reads.
+-->
+Kubernetes 以其强大的容器化应用编排能力而闻名，但随着集群规模扩大，
+对控制平面的需求可能成为性能瓶颈。其中一个主要挑战是确保从
+etcd 数据存储进行强一致性读，这通常需要资源密集型仲裁读取操作。
+
+<!--
+Today, the Kubernetes community is excited to announce a major improvement:
+_consistent reads from cache_, graduating to Beta in Kubernetes v1.31.
+
+### Why consistent reads matter
+-->
+今天，Kubernetes 社区很高兴地宣布一个重大改进：**基于缓存的一致性读**，
+已在 Kubernetes v1.31 中晋升至 Beta 阶段。
+
+### 为什么一致性读如此重要   {#why-consistent-reads-matter}
+
+<!--
+Consistent reads are essential for ensuring that Kubernetes components have an accurate view of the latest cluster state.
+Guaranteeing consistent reads is crucial for maintaining the accuracy and reliability of Kubernetes operations,
+enabling components to make informed decisions based on up-to-date information.
+In large-scale clusters, fetching and processing this data can be a performance bottleneck,
+especially for requests that involve filtering results.
+-->
+一致性读是确保 Kubernetes 组件准确了解最新集群状态的关键。
+保证一致性读对于保持 Kubernetes 操作准确性和可靠性至关重要，
+使组件能够根据最新信息做出明智决策。
+在大型集群中，数据的获取和处理往往会成为性能瓶颈，特别是那些需要过滤结果的请求。
+
+<!--
+While Kubernetes can filter data by namespace directly within etcd,
+any other filtering by labels or field selectors requires the entire dataset to be fetched from etcd and then filtered in-memory by the Kubernetes API server.
+This is particularly impactful for components like the kubelet,
+which only needs to list pods scheduled to its node - but previously required the API Server and etcd to process all pods in the cluster.
+-->
+虽然 Kubernetes 可以直接在 etcd 中按命名空间过滤数据，但如果按标签或字段选择器过滤，
+则需要从 etcd 获取整个数据集，然后由 Kubernetes API 服务器在内存中执行过滤操作。
+这对 Kubelet 等组件的影响尤为显著，因为 Kubelet 现在仅需列出调度到其节点的 Pod，
+而之前却需要 API 服务器和 etcd 处理集群中所有的 Pod。
+
+<!--
+### The breakthrough: Caching with confidence
+
+Kubernetes has long used a watch cache to optimize read operations.
+The watch cache stores a snapshot of the cluster state and receives updates through etcd watches.
+However, until now, it couldn't serve consistent reads directly, as there was no guarantee the cache was sufficiently up-to-date.
+-->
+### 突破：自信地缓存   {#the-breakthrough-Caching-with-confidence}
+
+Kubernetes 长期以来一直使用监视缓存来优化读取操作。
+监视缓存保存集群状态的快照，并通过对 etcd 的监视获取更新。
+然而，直到现在,它无法直接支持一致性读，因为没有机制保证缓存是最新的。
+
+<!--
+The _consistent reads from cache_ feature addresses this by leveraging etcd's
+[progress notifications](https://etcd.io/docs/v3.5/dev-guide/interacting_v3/#watch-progress)
+mechanism.
+These notifications inform the watch cache about how current its data is compared to etcd.
+When a consistent read is requested, the system first checks if the watch cache is up-to-date.
+-->
+**基于缓存的一致性读** 特性通过使用 etcd 的
+[进度通知](https://etcd.io/docs/v3.5/dev-guide/interacting_v3/#watch-progress)
+机制来解决这一问题。这些通知会向监视缓存说明其数据与 etcd 相比的新旧状态。
+当发出一致性读请求时，系统会首先检查监视缓存是否为最新状态。
+
+<!--
+If the cache is not up-to-date, the system queries etcd for progress notifications until it's confirmed that the cache is sufficiently fresh.
+Once ready, the read is efficiently served directly from the cache,
+which can significantly improve performance,
+particularly in cases where it would require fetching a lot of data from etcd.
+This enables requests that filter data to be served from the cache,
+with only minimal metadata needing to be read from etcd.
+-->
+如果缓存未更新到最新状态，系统会通过查询 etcd 的进度通知，直到确认缓存已经足够新。
+一旦缓存就绪，读取操作就可以直接从缓存中高效地获取数据，这可以显著提升性能，
+尤其是在需要从 etcd 获取大量数据的场景下。这种方式支持通过缓存处理数据过滤请求，
+仅需从 etcd 读取少量的元数据。
+
+<!--
+**Important Note:** To benefit from this feature, your Kubernetes cluster must be running etcd version 3.4.31+ or 3.5.13+.
+For older etcd versions, Kubernetes will automatically fall back to serving consistent reads directly from etcd.
+
+### Performance gains you'll notice
+
+This seemingly simple change has a profound impact on Kubernetes performance and scalability:
+-->
+**重要提示：** 要享受此特性带来的好处，你的 Kubernetes 集群需运行
+etcd 版本 3.4.31+ 或 3.5.13+。对于较早版本的 Etcd，Kubernetes
+将自动回退为直接从 etcd 提供一致性读。
+
+### 你将注意到的性能提升   {#performance-gains-youll-notice}
+
+这个看似简单的改动，对 Kubernetes 的性能和可扩展性有着深远影响:
+
+<!--
+* **Reduced etcd Load:** Kubernetes v1.31 can offload work from etcd,
+  freeing up resources for other critical operations.
+* **Lower Latency:** Serving reads from cache is significantly faster than fetching
+  and processing data from etcd. This translates to quicker responses for components,
+  improving overall cluster responsiveness.
+* **Improved Scalability:** Large clusters with thousands of nodes and pods will
+  see the most significant gains, as the reduction in etcd load allows the
+  control plane to handle more requests without sacrificing performance.
+-->
+* **降低 etcd 负载：** Kubernetes v1.31 可以将部分工作从 etcd 分载出去，
+  为其他关键操作释放资源。
+* **更低的延迟：** 从缓存读取数据的速度显著快于从 etcd 获取并处理数据。
+  这使组件的响应速度更快，提升了集群整体的响应能力。
+* **增强的可扩展性：** 拥有数千个节点和 Pod 的大型集群将获得最显著的性能增益，
+  因为 etcd 负载的降低使得控制平面可以在不牺牲性能的情况下处理更多请求。
+
+<!--
+**5k Node Scalability Test Results:** In recent scalability tests on 5,000 node
+clusters, enabling consistent reads from cache delivered impressive improvements:
+
+* **30% reduction** in kube-apiserver CPU usage
+* **25% reduction** in etcd CPU usage
+* **Up to 3x reduction** (from 5 seconds to 1.5 seconds) in 99th percentile pod LIST request latency
+-->
+**5 千节点扩缩容测试结果：** 在最近针对 5,000 节点集群的扩缩容测试中，
+启用基于缓存的一致性读带来了显著提升：
+
+* **kube-apiserver CPU 使用率降低 30%**
+* **etcd CPU 使用率降低 25%**
+* **第 99 百分位的 Pod 列表请求延迟出现了高至 3 倍的减少（从 5 秒降至 1.5 秒）**
+
+<!--
+### What's next?
+
+With the graduation to beta, consistent reads from cache are enabled by default,
+offering a seamless performance boost to all Kubernetes users running a supported
+etcd version.
+
+Our journey doesn't end here. Kubernetes community is actively exploring
+pagination support in the watch cache, which will unlock even more performance
+optimizations in the future.
+-->
+## 下一步是什么？   {#whats-next}
+
+随着基于缓存的一致性读特性晋升至 Beta 版，该特性已默认启用，为所有使用受支持 etcd
+版本的 Kubernetes 用户提供了无缝的性能提升。
+
+我们的探索并未止步于此。Kubernetes 社区正积极研究在监视缓存中加入分页支持，
+未来有望带来更多性能优化。
+
+<!--
+### Getting started
+
+Upgrading to Kubernetes v1.31 and ensuring you are using etcd version 3.4.31+ or
+3.5.13+ is the easiest way to experience the benefits of consistent reads from
+cache.
+If you have any questions or feedback, don't hesitate to reach out to the Kubernetes community.
+-->
+### 开始使用   {#getting-started}
+
+升级到 Kubernetes v1.31 并确保使用 etcd 版本 3.4.31+ 或 3.5.13+，
+是体验基于缓存的一致性读优势的最简单方法。如果有任何问题或反馈，不要犹豫，
+随时联系 Kubernetes 社区。
+
+<!--
+**Let us know how** _consistent reads from cache_ **transforms your Kubernetes experience!**
+
+Special thanks to @ah8ad3 and @p0lyn0mial for their contributions to this feature!
+-->
+请让我们知道**基于缓存的一致性读**如何改善了你的 Kubernetes 体验！
+
+特别感谢 @ah8ad3 和 @p0lyn0mial 对这一特性做出的贡献！