minisnap

Minimal snapshot store for durable state managers
Part of the mini-rs embeddable toolkit

minisnap gives you just enough: atomic, human-readable snapshots with zero hidden machinery.

🎯 Purpose

minisnap provides a simple, reliable way to serialize and restore a full copy of your application state to and from disk. It is designed to complement WAL-based systems like ministore by enabling:

• ✅ Fast recovery (skip replaying a long WAL)
• 🔒 Consistency tracking via logical sequence numbers
• 🧑‍💻 Human-readable snapshots (plain JSON + text metadata)
• 🔮 Future WAL compaction (truncate log after snapshot)

Snapshots are explicit — you decide when to create them. No background threads. No magic.

📦 Quick Start

[dependencies]
minisnap = "0.1"
serde = { version = "1.0", features = ["derive"] }

use minisnap::SnapStore;
use serde::{Deserialize, Serialize};

#[derive(Serialize, Deserialize, PartialEq, Debug)]
struct AppState { counter: u64 }

let store = SnapStore::new("./state");

// Save
store.create(&AppState { counter: 42 }, 10).await?; // seq = 10

// Restore
let (restored, seq): (AppState, u64) = store.restore().await?;
assert_eq!(restored.counter, 42);
assert_eq!(seq, 10);

💡 Snapshots are stored as two files:

• snapshot.json — pretty-printed JSON state
• snapshot.seq — plain-text sequence number (e.g., 10)

✅ Guarantees

⚠️ Atomic rename() requires a POSIX-compliant filesystem (ext4, XFS, APFS). Avoid FAT32.

🧩 Part of mini-rs

• ministore — durable WAL engine
• minisnap — snapshotting & log compaction (this crate)
• ministate — uses minisnap when the snapshot Cargo feature is enabled
• miniqueue — future WAL compaction

Used in:

• Arcella — component state snapshots
• walmq — queue metadata snapshots

📄 License

Dual-licensed under:

• Apache License 2.0
• MIT License

Choose the one that best fits your project.

minisnap — because sometimes, the best state is the one you can trust after a crash.
Part of the mini-rs family: simple, embeddable, reliable.