Upgrade to Pro
— share decks privately, control downloads, hide ads and more …
Speaker Deck
Features
Speaker Deck
PRO
Sign in
Sign up for free
Search
Search
Consensus: An Introduction to Raft
Search
Patrick Van Stee
July 23, 2013
Programming
22
3k
Consensus: An Introduction to Raft
Patrick Van Stee
July 23, 2013
Tweet
Share
More Decks by Patrick Van Stee
See All by Patrick Van Stee
Raft: Consensus for Rubyists
vanstee
140
7.1k
Elixir and Ecto
vanstee
5
940
Bootstrap
vanstee
8
790
HTTP API Design for iOS Applications
vanstee
11
640
Convergent Replicated Data Types
vanstee
4
770
Pour Over Brewing Method
vanstee
1
360
Celluloid & DCell
vanstee
4
550
Map Reduce & Ruby
vanstee
10
810
Other Decks in Programming
See All in Programming
そのAPI、誰のため? Androidライブラリ設計における利用者目線の実践テクニック
mkeeda
2
2.8k
Kiroで始めるAI-DLC
kaonash
2
630
OSS開発者という働き方
andpad
5
1.7k
請來的 AI Agent 同事們在寫程式時,怎麼用 pytest 去除各種幻想與盲點
keitheis
0
130
ProxyによるWindow間RPC機構の構築
syumai
3
1.2k
デザイナーが Androidエンジニアに 挑戦してみた
874wokiite
0
550
The Past, Present, and Future of Enterprise Java with ASF in the Middle
ivargrimstad
0
180
知っているようで知らない"rails new"の世界 / The World of "rails new" You Think You Know but Don't
luccafort
PRO
1
190
ユーザーも開発者も悩ませない TV アプリ開発 ~Compose の内部実装から学ぶフォーカス制御~
taked137
0
190
print("Hello, World")
eddie
2
530
アセットのコンパイルについて
ojun9
0
130
Swift Updates - Learn Languages 2025
koher
2
510
Featured
See All Featured
Rebuilding a faster, lazier Slack
samanthasiow
83
9.2k
Facilitating Awesome Meetings
lara
55
6.5k
Making Projects Easy
brettharned
117
6.4k
RailsConf 2023
tenderlove
30
1.2k
Art, The Web, and Tiny UX
lynnandtonic
303
21k
The Language of Interfaces
destraynor
161
25k
The Web Performance Landscape in 2024 [PerfNow 2024]
tammyeverts
9
810
ReactJS: Keep Simple. Everything can be a component!
pedronauck
667
120k
Reflections from 52 weeks, 52 projects
jeffersonlam
352
21k
Site-Speed That Sticks
csswizardry
10
820
Practical Orchestrator
shlominoach
190
11k
Creating an realtime collaboration tool: Agile Flush - .NET Oxford
marcduiker
31
2.2k
Transcript
Consensus An Introduction to Raft
con·sen·sus /kənˈsensəs/ Agreeing upon state across distributed processes even in
the presence of failures.
Problem • Distributed System • Consistency • Partition tolerance
Solution • Quorum • Replicated State Machines
Consensus Data —
We are sacrificing Availability
Why not Paxos? • Difficult to understand • Not practical
enough to implement
Raft A Practical Paxos
Components • Consensus Module • State Machine • Log
Consensus Module • Roles: Leader, Follower, and Candidate • Time
is divided into Terms • Commands: RequestVote and AppendEntries
Leader Accept commands from clients, commit entries, and send heartbeats
Follower Replicate state from leaders and vote for candidates Candidate Start and handle leader elections
Follower Candidate Leader Times out, Starts election Times out, Restarts
election Wins election Discovers new leader, Steps down Discovers current leader or new leader, Steps down
Term Higher numbers are used to determine leaders and check
log entries. The term is incremented each time an election is started. Any command with an old term is ignored.
Example Happy Log Entry
A B C Role: Leader Term: 1 Commit Index: 0
Log: [] Role: Follower Term: 1 Commit Index: 0 Log: [] Role: Follower Term: 1 Commit Index: 0 Log: []
A B C Role: Leader Term: 1 Commit Index: 0
Log: [˒] Role: Follower Term: 1 Commit Index: 0 Log: [] Role: Follower Term: 1 Commit Index: 0 Log: [] Leader receives command ˒
A B C Role: Leader Term: 1 Commit Index: 0
Log: [˒] Role: Follower Term: 1 Commit Index: 0 Log: [˒] Role: Follower Term: 1 Commit Index: 0 Log: [˒] Leader sends log entries to followers
A B C Role: Leader Term: 1 Commit Index: 1
Log: [˒] Role: Follower Term: 1 Commit Index: 0 Log: [˒] Role: Follower Term: 1 Commit Index: 0 Log: [˒] Majority of followers respond with success
A B C Role: Leader Term: 1 Commit Index: 1
Log: [˒] Role: Follower Term: 1 Commit Index: 1 Log: [˒] Role: Follower Term: 1 Commit Index: 1 Log: [˒] Leader sends commit index to followers and responds to client
Example Sad Log Entry
A B C Role: Leader Term: 1 Commit Index: 0
Log: [] Role: Follower Term: 1 Commit Index: 0 Log: [] Role: Follower Term: 1 Commit Index: 0 Log: []
A B C Role: Leader Term: 1 Commit Index: 0
Log: [˒] Role: Follower Term: 1 Commit Index: 0 Log: [] Role: Follower Term: 1 Commit Index: 0 Log: [] Leader receives command ˒
A B C Role: Leader Term: 1 Commit Index: 0
Log: [˒] Role: Follower Term: 1 Commit Index: 0 Log: [˒] Role: Follower Term: 1 Commit Index: 0 Log: [] Leader sends log entries to followers
A B C Role: Leader Term: 1 Commit Index: 0
Log: [˒] Role: Follower Term: 1 Commit Index: 0 Log: [˒] Role: Follower Term: 1 Commit Index: 0 Log: [] Majority of followers do not respond
A B C Role: Leader Term: 1 Commit Index: 0
Log: [˒] Role: Follower Term: 1 Commit Index: 0 Log: [˒] Role: Follower Term: 1 Commit Index: 0 Log: [˒] Leader continues to retry log entry
Example Leader Failure
A B C Role: Leader Term: 1 Commit Index: 0
Log: [] Role: Follower Term: 1 Commit Index: 0 Log: [] Role: Follower Term: 1 Commit Index: 0 Log: [] D Role: Follower Term: 1 Commit Index: 0 Log: []
A B C Role: Leader Term: 1 Commit Index: 0
Log: [] Role: Follower Term: 1 Commit Index: 0 Log: [] Role: Follower Term: 1 Commit Index: 0 Log: [] Followers do not receive heartbeat D Role: Follower Term: 1 Commit Index: 0 Log: []
A B C Role: Leader Term: 1 Commit Index: 0
Log: [] Role: Candidate Term: 2 Commit Index: 0 Log: [] Role: Follower Term: 1 Commit Index: 0 Log: [] First follower to timeout becomes candidate D Role: Follower Term: 1 Commit Index: 0 Log: []
A B C Role: Leader Term: 1 Commit Index: 0
Log: [] Role: Candidate Term: 2 Commit Index: 0 Log: [] Role: Follower Term: 2 Commit Index: 0 Log: [] Candidate starts election and requests votes D Role: Follower Term: 2 Commit Index: 0 Log: []
A B C Role: Leader Term: 1 Commit Index: 0
Log: [] Role: Leader Term: 2 Commit Index: 0 Log: [] Role: Follower Term: 2 Commit Index: 0 Log: [] Followers respond with votes D Role: Follower Term: 2 Commit Index: 0 Log: []
Extras • Log safety and compaction • Cluster changes
Real-life Application • Distributed lock server • Configuration management •
Background job storage
Smart People • Raft Paper by Diego Ongaro and John
Ousterhout • Raft Implementation • ThinkDistributed