petgraph-live

Status: coming soon. Implementation in progress. API not yet stable.

Graph cache, snapshot, and algorithms for petgraph 0.8.

Purpose

petgraph is excellent for building and traversing graphs. petgraph-live adds the operational layer missing for long-running processes:

Hot-reload cache — generic GenerationCache<G> that reuses a built graph until an external counter (e.g. an index generation, a file watch event) signals a change. No redundant rebuilds in serve mode.
Disk snapshot — persist and restore the cached graph across process restarts. Atomic writes, commit-keyed validity check, silent fallback to rebuild on mismatch or corruption.
Graph algorithms — unweighted metrics and connectivity analysis on petgraph 0.8 graphs, with no heavy dependencies (nalgebra, rand, etc.):
- metrics: diameter, radius, eccentricity, center, periphery
- connect: articulation points, bridges

All algorithms work on any DiGraph<N, E> — no wiki or domain concepts inside this crate.

Planned API

use petgraph_live::cache::GenerationCache;
use petgraph_live::metrics;
use petgraph_live::connect;

// Cache a graph, rebuild only when generation changes
let cache = GenerationCache::new();
let graph = cache.get_or_build(current_gen, || build_my_graph())?;

// Graph health metrics
let d = metrics::diameter(&graph);   // longest shortest path
let c = metrics::center(&graph);     // most central nodes

// Connectivity analysis
let ap = connect::articulation_points(&graph);  // removal disconnects graph
let br = connect::find_bridges(&graph);          // edge removal disconnects graph

Motivation

Built as a companion to llm-wiki, a git-backed wiki engine with MCP server. The graph cache and algorithm needs there are generic enough to live in a standalone crate on petgraph 0.8.

The only available alternative (graphalgs) is pinned to petgraph ^0.6.5 and appears unmaintained (last release 2023). petgraph-live targets petgraph 0.8 only and has no plans to support older versions.

Roadmap

cache::GenerationCache<G> with read-write lock, hit/miss semantics
metrics — diameter, radius, eccentricity, center, periphery (BFS, O(n·(n+e)))
connect — articulation points, bridges (DFS, O(n+e))
snapshot — serde-based disk persistence (petgraph serde-1 feature)
Docs and examples

License