Easy-Raft

A Java library based on the Raft algorithm that simplifies the complexity of building Raft clusters for users, making it easy to integrate and use for distributed consistency management

Features

• Leader election
• Log replication
• Snapshot
• Dynamic changes in cluster members

Quick Start

Deploy a 3-instance raft cluster on a local single machine by executing the following script:

cd raft-java-example && sh deploy.sh

This script will deploy three instances raft-node-1, raft-node-2, and raft-node-3 in the raft-java-example/env directory It will also create a client directory for testing raft cluster read and write functions After successful deployment, test write operations by executing the following script:

cd env/client
./bin/run_client.sh "list://127.0.0.1:8051,127.0.0.1:8052,127.0.0.1:8053" hello world

Test read operations by executing the following script:

./bin/run_client.sh "list://127.0.0.1:8051,127.0.0.1:8052,127.0.0.1:8053" hello

Usage

The following describes how to use the raft-java dependency library to implement a distributed storage system in the code.

Configure Dependency

No published to the Maven Central Repository yet, need to be manually installed locally

<dependency>
    <groupId>com.emptyovo</groupId>
    <artifactId>easy-raft-core</artifactId>
    <version>1.0-SNAPSHOT</version>
</dependency>

Define data write and read interfaces

message SetRequest {
    string key = 1;
    string value = 2;
}
message SetResponse {
    bool success = 1;
}
message GetRequest {
    string key = 1;
}
message GetResponse {
    string value = 1;
}
public interface ExampleService {
    Example.SetResponse set(Example.SetRequest request);
    Example.GetResponse get(Example.GetRequest request);
}

Server-side usage

1. Implement the StateMachine interface implementation class

// The three methods of this interface are mainly called by Raft internally
public interface StateMachine {
    /**
     * snapshot the data in the state machine and call it locally and periodically for each node
     * @param snapshotDir snapshot data output directory
     */
    void writeSnapshot(String snapshotDir);
    /**
     * Read snapshot to state machine, called when node starts
     * @param snapshotDir snapshot data directory
     */
    void readSnapshot(String snapshotDir);
    /**
     * Apply data to the state machine
     * @param dataBytes data binary
     */
    void apply(byte[] dataBytes);
}

2. Implement data write and read interfaces

// implementation class needs to contain the following members
private RaftNode raftNode;
private ExampleStateMachine stateMachine;

// Main logic of data writing
byte[] data = request.toByteArray();
// Synchronize data to raft cluster
boolean success = raftNode.replicate(data, Raft.EntryType.ENTRY_TYPE_DATA);
Example.SetResponse response = Example.SetResponse.newBuilder().setSuccess(success).build();