# consensus algorithm

A consensus algorithm is a distributed-computing procedure that enables distributed processes or nodes to agree on a single value or decision despite failures or network interruptions.

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## 【etcd】读路径与一致性：ReadIndex、Serializable 与 Lease read

DevFeed: [【etcd】读路径与一致性：ReadIndex、Serializable 与 Lease read](<https://devfeed.tech/articles/etcd-readindex-serializable-lease-read-33990.md>)

Original publisher: [Read original article](<https://quant67.com/post/etcd/08-read-consistency/08-read-consistency.html>)

Author: Liao Tonglang

Published: 2026-08-26T00:00:00Z

Content type: tutorial

Language: zh

Sources: [土法炼钢 - 系统与基础设施](<https://devfeed.tech/sources/source-4.md>)

Topics: [etcd](<https://devfeed.tech/topics/etcd.md>), [Raft](<https://devfeed.tech/topics/raft.md>), [consensus algorithm](<https://devfeed.tech/topics/consensus-algorithm.md>), [Kubernetes](<https://devfeed.tech/topics/kubernetes.md>)

Tags: [consistency](<https://devfeed.tech/tags/consistency.md>), [distributed](<https://devfeed.tech/tags/distributed.md>), [etcd](<https://devfeed.tech/tags/etcd.md>), [follower](<https://devfeed.tech/tags/follower.md>), [k8s](<https://devfeed.tech/tags/k8s.md>), [keepalive](<https://devfeed.tech/tags/keepalive.md>), [kubernetes](<https://devfeed.tech/tags/kubernetes.md>), [lease](<https://devfeed.tech/tags/lease.md>), [linearizable](<https://devfeed.tech/tags/linearizable.md>), [raft](<https://devfeed.tech/tags/raft.md>), [readindex](<https://devfeed.tech/tags/readindex.md>), [resourceversion](<https://devfeed.tech/tags/resourceversion.md>), [revision](<https://devfeed.tech/tags/revision.md>), [serializable](<https://devfeed.tech/tags/serializable.md>), [ttl](<https://devfeed.tech/tags/ttl.md>), [v3-5](<https://devfeed.tech/tags/v3-5.md>), [v3-5-33](<https://devfeed.tech/tags/v3-5-33.md>)

### AI overview

This tutorial explains read consistency in etcd v3.5.33. It distinguishes default linearizable reads using ReadIndex, local Serializable reads that may be stale on followers, and Lease RPC reads handled by the leader outside the Raft log. It also discusses leader changes, apply-index waiting, follower forwarding, MVCC history reads, and implications for Kubernetes apiserver clients.

### Source excerpt

分列 etcd v3.5.33 三种读语义：默认线性一致读的 ReadIndex 循环、Serializable 本地读、Raft ReadOnlyLeaseBased 与不经 Raft 的 Lease 路径；follower 读风险与 K8s 期望。

## Understanding and scaling Raft

DevFeed: [Understanding and scaling Raft](<https://devfeed.tech/articles/understanding-and-scaling-raft-39636.md>)

Original publisher: [Read original article](<https://www.gauravsarma.com/posts/2025-04-04_understanding-and-scaling-raft>)

Published: 2025-04-04T00:00:00Z

Content type: tutorial

Language: en

Sources: [Gaurav Sarma's Blog](<https://devfeed.tech/sources/gaurav-sarma-s-blog.md>)

Topics: [Raft](<https://devfeed.tech/topics/raft.md>), [consensus algorithm](<https://devfeed.tech/topics/consensus-algorithm.md>), [distributed-systems](<https://devfeed.tech/topics/distributed-systems.md>), [scaling](<https://devfeed.tech/topics/scaling.md>), [CockroachDB](<https://devfeed.tech/topics/cockroachdb.md>), [Databases](<https://devfeed.tech/topics/databases.md>)

Tags: [cockroachdb](<https://devfeed.tech/tags/cockroachdb.md>), [consensus-algorithm](<https://devfeed.tech/tags/consensus-algorithm.md>), [databases](<https://devfeed.tech/tags/databases.md>), [distributed-systems](<https://devfeed.tech/tags/distributed-systems.md>), [raft](<https://devfeed.tech/tags/raft.md>), [replication](<https://devfeed.tech/tags/replication.md>), [scaling](<https://devfeed.tech/tags/scaling.md>)

### AI overview

This tutorial explains the Raft consensus algorithm, including leader election, log replication, safety guarantees, and the network cost of consensus. It also introduces the Multi-Raft pattern for scaling distributed databases by splitting data into ranges with independent Raft groups.

### Source excerpt

. [Understanding and Scaling Raft](understanding-and-scaling-raft-cover...

## In-Place etcd Upgrades Beneath Kubernetes in Air-Gapped Clusters

DevFeed: [In-Place etcd Upgrades Beneath Kubernetes in Air-Gapped Clusters](<https://devfeed.tech/articles/the-horrors-of-upgrading-etcd-beneath-kubernetes-29738.md>)

Original publisher: [Read original article](<https://goteleport.com/blog/kubernetes-and-offline-etcd-upgrades/>)

Author: info@goteleport.com (Kevin Nisbet)

Published: 2018-07-03T00:00:00Z

Content type: article

Language: en

Sources: [Teleport](<https://devfeed.tech/sources/teleport.md>)

Topics: [Kubernetes](<https://devfeed.tech/topics/kubernetes.md>), [Kubernetes clusters](<https://devfeed.tech/topics/kubernetes-clusters.md>), [distributed-systems](<https://devfeed.tech/topics/distributed-systems.md>), [consensus algorithm](<https://devfeed.tech/topics/consensus-algorithm.md>), [Raft](<https://devfeed.tech/topics/raft.md>)

Tags: [clusters](<https://devfeed.tech/tags/clusters.md>), [distributed](<https://devfeed.tech/tags/distributed.md>), [distributed-systems](<https://devfeed.tech/tags/distributed-systems.md>), [kubernetes](<https://devfeed.tech/tags/kubernetes.md>), [raft](<https://devfeed.tech/tags/raft.md>), [upgrades](<https://devfeed.tech/tags/upgrades.md>)

### AI overview

An interview examines the challenges of upgrading and rolling back etcd in place beneath Kubernetes deployments running in autonomous, air-gapped, or inaccessible environments.

### Source excerpt

We dig into the challenges of in-place etcd upgrades beneath autonomous Kubernetes clusters running in air-gapped environments.