openmessaging/dledger

Introduction

A raft-based java library for building high-available, high-durable, strong-consistent commitlog, which could act as the persistent layer for distributed storage system, i.e. messaging, streaming, kv, db, etc.

Dledger has added many new features that are not described in the original paper. It has been proven to be a true production ready product.

Features

• Leader election
• Preferred leader election
• Pre-vote protocol
• High performance, high reliable storage support
• Parallel log replication between leader and followers
• Asynchronous replication
• State machine
• Multi-Raft
• High tolerance of symmetric network partition
• High tolerance of asymmetric network partition
• Jepsen verification with fault injection

New features waiting to be added

• Snapshot (working in progress)
• Dynamic membership & configuration change
• SSL/TLS support

Quick Start

Prerequisite

• 64bit JDK 1.8+

• Maven 3.2.x

How to Build

mvn clean install -DskipTests

Run Command Line

Help

Print Help in Command Line

java -jar example/target/dledger-example.jar

Appender

A high-available, high-durable, strong-consistent, append-only log store.

Start a Standalone Appender Server

java -jar example/target/dledger-example.jar appender

Append Data to Appender

java -jar example/target/dledger-example.jar append -d "Hello World"

After this command, you have appended a log which contains "Hello World" to the appender.

Get Data from Appender

java -jar example/target/dledger-example.jar get -i 0

After this command, you have got the log which contains "Hello World" from the appender.

RegisterModel

A simple multi-register model

Start a Standalone RegisterModel Server

java -jar example/target/dledger-example.jar register

Write Value for a Key

java -jar example/target/dledger-example.jar write -k 13 -v 31

After this command, you have written a key-value pair which is <13, 31> to the register model.

Read Value for a Key

java -jar example/target/dledger-example.jar read -k 13

After this command, you have read the value 31 for the key 13 from the register model.

Contributing

We always welcome new contributions, whether for trivial cleanups, big new features. We are always interested in adding new contributors. What we look for are series of contributions, good taste and ongoing interest in the project. If you are interested in becoming a committer, please let one of the existing committers know and they can help you walk through the process.

License

Apache License, Version 2.0 Copyright (C) Apache Software Foundation