raftscope

A browser visualization of the Raft consensus algorithm, inspired by The Secret Lives of Data. Originally vanilla JS; now a Rust → WebAssembly rewrite that renders a live SVG via web-sys (no UI framework).

Still a decent space heater while your browser re-renders SVG at 60fps.

Run it

rustup target add wasm32-unknown-unknown
cargo install trunk

trunk serve   # dev server with hot reload at http://localhost:8080

trunk build --release   # production bundle into dist/
cargo test              # pure protocol/state tests, no browser needed

Controls

Drag the timeline slider to scrub through history; the speed slider sets the simulation rate. Click a server or in-flight message for details, right-click for actions. Keyboard shortcuts:

Key	Action
space / .	pause / resume
c	client request to the leader
r	restart the leader
t	spread election timers (avoid split vote)
a	align election timers (force split vote)
l	set up a log-replication scenario
b	resume all servers
f	discard the future and continue from here
?	help

Architecture

Three layers (ports of the original raft.js / state.js / script.js):

• src/raft.rs — the Raft protocol, pure Rust. Model::update is one tick.
• src/state.rs — time-travel checkpoint history behind the timeline slider.
• src/lib.rs — all DOM/SVG rendering and input handling via web-sys.

See CLAUDE.md for the gotchas worth knowing before you touch the code.

Deploy

Pushing to main triggers .github/workflows/deploy.yml, which builds with Trunk and publishes to GitHub Pages (andygeorge.github.io/raftscope). Set Settings → Pages → Source to GitHub Actions once to enable it.

License

ISC License, © 2014 Stanford University — see LICENSE.

The original RaftScope license was an ISC variant whose wording deviated just enough that GitHub's license detector couldn't recognize it. The LICENSE text has been replaced with the canonical SPDX ISC template (and/or instead of and, THE AUTHOR instead of AUTHOR(S)) so GitHub identifies it correctly. The legal terms are unchanged; only the phrasing was normalized.

For the record, the original license text read verbatim:

Copyright (c) 2014 Stanford University

Permission to use, copy, modify, and distribute this software for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR(S) DISCLAIM ALL WARRANTIES
WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL AUTHORS BE LIABLE FOR
ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.