缘起

最近阅读 [云原生分布式存储基石：etcd深入解析] (杜军 , 2019.1)
本系列笔记拟采用golang练习之

raft分布式一致性算法

分布式存储系统通常会通过维护多个副本来进行容错，
以提高系统的可用性。
这就引出了分布式存储系统的核心问题——如何保证多个副本的一致性？

Raft算法把问题分解成了四个子问题：
1. 领袖选举（leader election）、
2. 日志复制（log replication）、
3. 安全性（safety）
4. 成员关系变化（membership changes）
这几个子问题。

源码gitee地址：
https://gitee.com/ioly/learning.gooop

目标

根据raft协议，实现高可用分布式强一致的kv存储

子目标（Day 11）

虽然Leader State还有细节没处理完，但应该能启动并提供基本服务了
添加外围功能，为首次“点火”做准备：
- config/tRaftConfig：从本地json文件读取集群节点配置，提供IRaftConfig/IRaftNodeConfig的实现
- lsm/tRaftLSMImplement：提供对顶层接口IRaftLSM的实现，将“配置/kv存储/节点通讯”三大块粘合起来
- server/IRaftKVServer：server启动器接口
- server/tRaftKVServer: server启动器的实现，监听raft rpc和kv rpc

config/tRaftConfig.go

从本地json文件读取集群节点配置，提供IRaftConfig/IRaftNodeConfig的实现

package config

import (
    "encoding/json"
    "os"
)

type tRaftConfig struct {
    ID string
    Nodes []*tRaftNodeConfig
}

type tRaftNodeConfig struct {
    ID string
    Endpoint string
}

func (me *tRaftConfig) GetID() string {
    return me.ID
}

func (me *tRaftConfig) GetNodes() []IRaftNodeConfig {
    a := make([]IRaftNodeConfig, len(me.Nodes))
    for i,it := range me.Nodes {
        a[i] = it
    }
    return a
}


func (me *tRaftNodeConfig) GetID() string {
    return me.ID
}

func (me *tRaftNodeConfig) GetEndpoint() string {
    return me.Endpoint
}

func LoadJSONFile(file string) IRaftConfig {
    data, err := os.ReadFile(file)
    if err != nil {
        panic(err)
    }

    c := new(tRaftConfig)
    err = json.Unmarshal(data, c)
    if err != nil {
        panic(err)
    }

    return c
}

lsm/tRaftLSMImplement.go

提供对顶层接口IRaftLSM的实现，将“配置/kv存储/节点通讯”三大块粘合起来，并添加诊断日志。

package lsm

import (
    "learning/gooop/etcd/raft/common"
    "learning/gooop/etcd/raft/config"
    "learning/gooop/etcd/raft/logger"
    "learning/gooop/etcd/raft/rpc"
    "learning/gooop/etcd/raft/rpc/client"
    "learning/gooop/etcd/raft/store"
    "sync"
)

type tRaftLSMImplement struct {
    tEventDrivenModel
    mInitOnce sync.Once

    mConfig config.IRaftConfig
    mStore store.ILogStore
    mClientService client.IRaftClientService
    mState IRaftState
}


// trigger: init()
// args: empty
const meInit = "lsm.Init"

// trigger: HandleStateChanged()
// args: IRaftState
const meStateChanged = "lsm.StateChnaged"

func (me *tRaftLSMImplement) init() {
    me.mInitOnce.Do(func() {
        me.initEventHandlers()
        me.raise(meInit)
    })
}

func (me *tRaftLSMImplement) initEventHandlers() {
    // write only
    me.hookEventsForConfig()
    me.hookEventsForStore()
    me.hookEventsForPeerService()
    me.hookEventsForState()
}

func (me *tRaftLSMImplement) hookEventsForConfig() {
    me.hook(meInit, func(e string, args ...interface{}) {
        logger.Logf("tRaftLSMImplement.init, ConfigFile = %v", common.ConfigFile)
        me.mConfig = config.LoadJSONFile(common.ConfigFile)
    })
}

func (me *tRaftLSMImplement) hookEventsForStore() {
    me.hook(meInit, func(e string, args ...interface{}) {
        logger.Logf("tRaftLSMImplement.init, DataFile = %v", common.DataFile)
        err, db := store.NewBoltStore(common.DataFile)
        if err != nil {
            panic(err)
        }
        me.mStore = db
    })
}


func (me *tRaftLSMImplement) hookEventsForPeerService() {
    me.hook(meInit, func(e string, args ...interface{}) {
        me.mClientService = client.NewRaftClientService(me.mConfig)
    })
}

func (me *tRaftLSMImplement) hookEventsForState() {
    me.hook(meInit, func(e string, args ...interface{}) {
        me.mState = newFollowerState(me, me.mStore.LastCommittedTerm())
        me.mState.Start()
    })

    me.hook(meStateChanged, func(e string, args ...interface{}) {
        state := args[0].(IRaftState)
        logger.Logf("tRaftLSMImplement.StateChanged, %v", state.Role())

        me.mState = state
        state.Start()
    })
}


func (me *tRaftLSMImplement) Config() config.IRaftConfig {
    return me.mConfig
}

func (me *tRaftLSMImplement) Store() store.ILogStore {
    return me.mStore
}

func (me *tRaftLSMImplement) HandleStateChanged(state IRaftState) {
    me.raise(meStateChanged, state)
}

func (me *tRaftLSMImplement) RaftClientService() client.IRaftClientService {
    return me.mClientService
}

func (me *tRaftLSMImplement) Heartbeat(cmd *rpc.HeartbeatCmd, ret *rpc.HeartbeatRet) error {
    state := me.mState
    e := state.Heartbeat(cmd, ret)
    logger.Logf("tRaftLSMImplement.Heartbeat, state=%v, cmd=%v, ret=%v, err=%v", cmd, ret, e)
    return e
}

func (me *tRaftLSMImplement) AppendLog(cmd *rpc.AppendLogCmd, ret *rpc.AppendLogRet) error {
    state := me.mState
    e := state.AppendLog(cmd, ret)
    logger.Logf("tRaftLSMImplement.AppendLog, state=%v, cmd=%v, ret=%v, err=%v", cmd, ret, e)
    return e
}

func (me *tRaftLSMImplement) CommitLog(cmd *rpc.CommitLogCmd, ret *rpc.CommitLogRet) error {
    state := me.mState
    e := state.CommitLog(cmd, ret)
    logger.Logf("tRaftLSMImplement.CommitLog, state=%v, cmd=%v, ret=%v, err=%v", cmd, ret, e)
    return e
}

func (me *tRaftLSMImplement) RequestVote(cmd *rpc.RequestVoteCmd, ret *rpc.RequestVoteRet) error {
    state := me.mState
    e := state.RequestVote(cmd, ret)
    logger.Logf("tRaftLSMImplement.RequestVote, state=%v, cmd=%v, ret=%v, err=%v", cmd, ret, e)
    return e
}

func (me *tRaftLSMImplement) ExecuteKVCmd(cmd *rpc.KVCmd, ret *rpc.KVRet) error {
    state := me.mState
    e := state.ExecuteKVCmd(cmd, ret)
    logger.Logf("tRaftLSMImplement.ExecuteKVCmd, state=%v, cmd=%v, ret=%v, err=%v", cmd, ret, e)
    return e
}

func (me *tRaftLSMImplement) State() IRaftState {
    return me.mState
}

func NewRaftLSM() IRaftLSM {
    it := new(tRaftLSMImplement)
    it.init()
    return it
}

server/IRaftKVServer.go

server启动器接口

package server

type IRaftKVServer interface {
    BeginServeTCP(port int) error
}

server/tRaftKVServer.go

server启动器的实现，监听raft rpc和kv rpc

package server

import (
    "fmt"
    "learning/gooop/etcd/raft/lsm"
    rrpc "learning/gooop/etcd/raft/rpc"
    "learning/gooop/saga/mqs/logger"
    "net"
    "net/rpc"
    "time"
)

type tRaftKVServer int

func (me *tRaftKVServer) BeginServeTCP(port int) error {
    logger.Logf("tRaftKVServer.BeginServeTCP, starting, port=%v", port)

    // resolve address
    addy, err := net.ResolveTCPAddr("tcp", fmt.Sprintf("0.0.0.0:%d", port))
    if err != nil {
        return err
    }

    // create raft lsm singleton
    raftLSM := lsm.NewRaftLSM()

    // register raft rpc server
    rserver := &RaftRPCServer {
        mRaftLSM : raftLSM,
    }
    err = rpc.Register(rserver)
    if err != nil {
        return err
    }

    // register kv rpc server
    kserver := &KVStoreRPCServer{
        mRaftLSM: raftLSM,
    }
    err = rpc.Register(kserver)
    if err != nil {
        return err
    }

    inbound, err := net.ListenTCP("tcp", addy)
    if err != nil {
        return err
    }
    go rpc.Accept(inbound)

    logger.Logf("tRaftKVServer.BeginServeTCP, service ready at port=%v", port)
    return nil
}

// RaftRPCServer exposes a raft rpc service
type RaftRPCServer struct {
    mRaftLSM lsm.IRaftLSM
}

// Heartbeat leader to follower
func (me *RaftRPCServer) Heartbeat(cmd *rrpc.HeartbeatCmd, ret *rrpc.HeartbeatRet) error {
    e := me.mRaftLSM.Heartbeat(cmd, ret)
    logger.Logf("RaftRPCServer.Heartbeat, cmd=%v, ret=%v, e=%v", cmd, ret, e)
    return e
}

// AppendLog leader to follower
func (me *RaftRPCServer) AppendLog(cmd *rrpc.AppendLogCmd, ret *rrpc.AppendLogRet) error {
    e := me.mRaftLSM.AppendLog(cmd, ret)
    logger.Logf("RaftRPCServer.AppendLog, cmd=%v, ret=%v, e=%v", cmd, ret, e)
    return e
}

// CommitLog leader to follower
func (me *RaftRPCServer) CommitLog(cmd *rrpc.CommitLogCmd, ret *rrpc.CommitLogRet) error {
    e := me.mRaftLSM.CommitLog(cmd, ret)
    logger.Logf("RaftRPCServer.CommitLog, cmd=%v, ret=%v, e=%v", cmd, ret, e)
    return e
}

// RequestVote candidate to others
func (me *RaftRPCServer) RequestVote(cmd *rrpc.RequestVoteCmd, ret *rrpc.RequestVoteRet) error {
    e := me.mRaftLSM.RequestVote(cmd, ret)
    logger.Logf("RaftRPCServer.RequestVote, cmd=%v, ret=%v, e=%v", cmd, ret, e)
    return e
}

// Ping to keep alive
func (me *RaftRPCServer) Ping(cmd *rrpc.PingCmd, ret *rrpc.PingRet) error {
    ret.SenderID = me.mRaftLSM.Config().GetID()
    ret.Timestamp = time.Now().UnixNano()

    logger.Logf("RaftRPCServer.Ping, cmd=%v, ret=%v", cmd, ret)
    return nil
}

// KVStoreRPCServer expose a kv storage service
type KVStoreRPCServer struct {
    mRaftLSM lsm.IRaftLSM
}

// ExecuteKVCmd leader to follower
func (me *KVStoreRPCServer) ExecuteKVCmd(cmd *rrpc.KVCmd, ret *rrpc.KVRet) error {
    e := me.mRaftLSM.ExecuteKVCmd(cmd, ret)
    logger.Logf("KVStoreRPCServer.ExecuteKVCmd, cmd=%v, ret=%v, e=%v", cmd, ret, e)
    return e
}

（未完待续）

本文来自：简书

感谢作者：老罗话编程

查看原文：手撸golang etcd raft协议之11