Just another Raft implementation for Java.
参考自Raft论文和Raft作者的开源实现LogCabin。
- leader选举
- 日志复制
- snapshot
- 集群成员动态更变
<dependency>
<groupId>com.github.wenweihu86.raft</groupId>
<artifactId>raft-java-core</artifactId>
<version>1.1.0</version>
</dependency>
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);
}
- 实现状态机StateMachine接口实现类
// 该接口三个方法主要是给Raft内部调用
public interface StateMachine {
/**
* 对状态机中数据进行snapshot,每个节点本地定时调用
* @param snapshotDir snapshot数据输出目录
*/
void writeSnapshot(String snapshotDir);
/**
* 读取snapshot到状态机,节点启动时调用
* @param snapshotDir snapshot数据目录
*/
void readSnapshot(String snapshotDir);
/**
* 将数据应用到状态机
* @param dataBytes 数据二进制
*/
void apply(byte[] dataBytes);
}
- 实现数据写入和读取接口
// ExampleService实现类中需要包含以下成员
private RaftNode raftNode;
private ExampleStateMachine stateMachine;
// 数据写入主要逻辑
byte[] data = request.toByteArray();
// 数据同步写入raft集群
boolean success = raftNode.replicate(data, Raft.EntryType.ENTRY_TYPE_DATA);
Example.SetResponse response = Example.SetResponse.newBuilder().setSuccess(success).build();
// 数据读取主要逻辑,由具体应用状态机实现
Example.GetResponse response = stateMachine.get(request);
- 服务端启动逻辑
// 初始化RPCServer
RPCServer server = new RPCServer(localServer.getEndPoint().getPort());
// 应用状态机
ExampleStateMachine stateMachine = new ExampleStateMachine();
// 设置Raft选项,比如:
RaftOptions.snapshotMinLogSize = 10 * 1024;
RaftOptions.snapshotPeriodSeconds = 30;
RaftOptions.maxSegmentFileSize = 1024 * 1024;
// 初始化RaftNode
RaftNode raftNode = new RaftNode(serverList, localServer, stateMachine);
// 注册Raft节点之间相互调用的服务
RaftConsensusService raftConsensusService = new RaftConsensusServiceImpl(raftNode);
server.registerService(raftConsensusService);
// 注册给Client调用的Raft服务
RaftClientService raftClientService = new RaftClientServiceImpl(raftNode);
server.registerService(raftClientService);
// 注册应用自己提供的服务
ExampleService exampleService = new ExampleServiceImpl(raftNode, stateMachine);
server.registerService(exampleService);
// 启动RPCServer,初始化Raft节点
server.start();
raftNode.init();