VarveDB

VarveDB is a high-performance, embedded, append-only event store for Rust, powered by LMDB (via heed) and rkyv.

It is designed for event sourcing, offering strongly-typed events, zero-copy deserialization, and optimistic concurrency control.

Features

Append-Only Log: Immutable event history.
Strongly Typed: Events and metadata are defined by user structs.
Zero-Copy: Efficient access using rkyv.
Optimistic Concurrency: ExpectedVersion support for safer writes.
Embedded: Runs in-process, no external server required.

Getting Started

Add varvedb to your Cargo.toml.

[dependencies]
varvedb = "0.2.1"
rkyv = "0.7" # Check version compatibility
serde = { version = "1.0", features = ["derive"] }

Basic Usage

use varvedb::{Varve, Payload, ExpectedVersion};
use varvedb::traits::MetadataExt;
use rkyv::{Archive, Serialize, Deserialize};

#[derive(Archive, Serialize, Deserialize, Debug)]
#[archive(derive(Debug))]
#[archive(check_bytes)]
struct MyEvent {
    data: String,
}

#[derive(Archive, Serialize, Deserialize, Debug)]
#[archive(derive(Debug))]
#[archive(check_bytes)]
struct MyMetadata {
    stream_id: u128,
    version: u32,
}

impl MetadataExt for MyMetadata {
    fn stream_id(&self) -> u128 { self.stream_id }
    fn version(&self) -> u32 { self.version }
}

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let mut db = Varve::open("my_db.mdb")?;

    let event = MyEvent { data: "Hello".into() };
    let metadata = MyMetadata { stream_id: 1, version: 1 };
    
    db.append(Payload::new(event, metadata), ExpectedVersion::Auto)?;

    for result in db.iter()? {
        println!("Event: {:?}", result?);
    }

    Ok(())
}

Architecture

Varve: The main facade for interacting with the database.
Storage: Manages the LMDB environment.
Processor: A framework for consuming events and tracking progress.

License