raft算法伪代码，包含超时选举，节点同步

好的，下面是RAFT算法的伪代码，包含超时选举和节点同步：

// 初始化节点
NODE_ID = unique_id()
CURRENT_TERM = 0
VOTED_FOR = null
LOG = []
NEXT_INDEX = {for each server: 1}
MATCH_INDEX = {for each server: 0}

// 启动节点
function start():
    // 启动定时器
    start_election_timeout()

    // 进入循环，监听事件
    while true:
        message = receive_message()

        if message.type == "append_entries":
            handle_append_entries(message)
        else if message.type == "request_vote":
            handle_request_vote(message)
        else if message.type == "response":
            handle_response(message)

        // 检测是否超时，如果超时则发起选举
        if election_timeout():
            start_election()

// 处理附加日志请求
function handle_append_entries(message):
    if message.term < CURRENT_TERM:
        send_response(false)
        return

    CURRENT_TERM = message.term
    VOTED_FOR = null
    stop_election_timeout()

    // 检测前一条日志是否匹配
    if LOG[message.prev_log_index].term != message.prev_log_term:
        send_response(false)
        return

    // 添加新日志
    LOG = LOG[:message.prev_log_index + 1] + message.entries + LOG[message.prev_log_index + 1:]

    // 更新提交索引
    if message.leader_commit > COMMIT_INDEX:
        COMMIT_INDEX = min(message.leader_commit, len(LOG) - 1)

    send_response(true)

// 处理投票请求
function handle_request_vote(message):
    if message.term < CURRENT_TERM:
        send_response(false)
        return

    last_log_index = len(LOG) - 1
    last_log_term = LOG[last_log_index].term

    if message.last_log_term < last_log_term or (message.last_log_term == last_log_term and message.last_log_index < last_log_index):
        send_response(false)
        return

    if VOTED_FOR is null or VOTED_FOR == message.candidate_id:
        CURRENT_TERM = message.term
        VOTED_FOR = message.candidate_id
        stop_election_timeout()
        send_response(true)
    else:
        send_response(false)

// 处理响应
function handle_response(message):
    if message.success:
        NEXT_INDEX[message.server_id] = message.next_index
        MATCH_INDEX[message.server_id] = message.next_index - 1

        // 如果已经提交，更新提交索引
        for i in range(COMMIT_INDEX + 1, len(LOG)):
            if LOG[i].term == CURRENT_TERM and sum(1 for j in MATCH_INDEX.values() if j >= i) > len(MATCH_INDEX) / 2:
                COMMIT_INDEX = i
    else:
        NEXT_INDEX[message.server_id] = message.next_index

// 开始选举
function start_election():
    CURRENT_TERM += 1
    VOTED_FOR = NODE_ID
    votes = 1
    stop_election_timeout()

    // 发送投票请求
    for server_id in all_servers():
        if server_id != NODE_ID:
            send_request_vote(server_id)

    // 等待投票结果
    while votes <= len(all_servers()) / 2:
        message = receive_message()

        if message.type == "request_vote_response" and message.term == CURRENT_TERM and message.vote_granted:
            votes += 1
        elif message.type == "append_entries" and message.term >= CURRENT_TERM:
            start_election()
            return

    // 选举成功，成为领导者
    become_leader()

// 成为领导者
function become_leader():
    // 初始化 next_index 和 match_index
    for server_id in all_servers():
        NEXT_INDEX[server_id] = len(LOG) + 1
        MATCH_INDEX[server_id] = 0

    // 开始发送心跳
    while true:
        for server_id in all_servers():
            if server_id != NODE_ID:
                // 发送附加日志请求
                prev_log_index = NEXT_INDEX[server_id] - 1
                prev_log_term = LOG[prev_log_index].term
                entries = LOG[NEXT_INDEX[server_id]:]
                send_append_entries(server_id, prev_log_index, prev_log_term, entries, COMMIT_INDEX)

        // 等待响应
        if some_response_received():
            // 如果已经提交，更新提交索引
            for i in range(COMMIT_INDEX + 1, len(LOG)):
                if LOG[i].term == CURRENT_TERM and sum(1 for j in MATCH_INDEX.values() if j >= i) > len(MATCH_INDEX) / 2:
                    COMMIT_INDEX = i

        // 如果有节点落后了，发送更小的日志条目
        for server_id in all_servers():
            if server_id != NODE_ID and NEXT_INDEX[server_id] <= len(LOG):
                send_append_entries(server_id, NEXT_INDEX[server_id] - 1, LOG[NEXT_INDEX[server_id] - 1].term, LOG[NEXT_INDEX[server_id]:], COMMIT_INDEX)

        // 等待一段时间后再次发送心跳
        sleep(HEARTBEAT_INTERVAL)

// 发送附加日志请求
function send_append_entries(server_id, prev_log_index, prev_log_term, entries, leader_commit):
    // 构造请求消息
    message = {
        "type": "append_entries",
        "term": CURRENT_TERM,
        "leader_id": NODE_ID,
        "prev_log_index": prev_log_index,
        "prev_log_term": prev_log_term,
        "entries": entries,
        "leader_commit": leader_commit
    }

    // 发送请求消息
    send_message(server_id, message)

// 发送投票请求
function send_request_vote(server_id):
    // 构造请求消息
    message = {
        "type": "request_vote",
        "term": CURRENT_TERM,
        "candidate_id": NODE_ID,
        "last_log_index": len(LOG) - 1,
        "last_log_term": LOG[len(LOG) - 1].term
    }

    // 发送请求消息
    send_message(server_id, message)

// 发送响应
function send_response(success, server_id, next_index):
    // 构造响应消息
    message = {
        "type": "response",
        "term": CURRENT_TERM,
        "success": success,
        "server_id": NODE_ID,
        "next_index": next_index
    }

    // 发送响应消息
    send_message(server_id, message)

这段代码实现了RAFT算法的关键步骤，包括超时选举和节点同步。其中，超时选举是通过定时器和投票请求实现的，而节点同步是通过附加日志请求和响应实现的。具体来说，当节点超时时，它会发送投票请求并等待响应，如果收到超过半数的投票，则成为领导者；领导者会周期性地发送附加日志请求来同步节点，并等待响应。如果有节点落后了，领导者会发送更小的日志条目来加速同步。最终，如果有足够多的节点接受了某个日志条目，领导者就可以将其提交。