raft算法选主用伪代码实现

下面是Raft算法选主的伪代码实现：

1. 初始化
   currentTerm = 0
   votedFor = null
   log[] = []

2. 处理请求投票请求
   if (request.term < currentTerm)
      return false
   else if (request.term > currentTerm)
   {
      currentTerm = request.term
      votedFor = null
   }
   
   if (votedFor is null or votedFor == request.candidateId)
   {
      if (candidate’s log is at least as up-to-date as receiver’s log)
      {
         votedFor = request.candidateId
         return true
      }
   }
   return false
   
3. 处理心跳
   if (request.term < currentTerm)
      return false
      
   currentTerm = request.term
   return true
   
4. 选主定时器超时
   startElection()
   
5. 开始新一轮选举
   currentTerm++
   votedFor = self
   resetElectionTimer()
   sendRequestVote()
   
6. 发送投票请求
   for each peer
      sendRequestVote()
      
7. 收到投票
   if (request.term < currentTerm)
      return false
      
   if (votedFor is null or votedFor == request.candidateId)
   {
      if (candidate’s log is at least as up-to-date as receiver’s log)
      {
         votedFor = request.candidateId
         resetElectionTimer()
         return true
      }
   }
   return false
   
8. 成为领导者
   nextIndex[] = [last log index + 1] * N
   matchIndex[] = [0] * N
   sendAppendEntries()
   
9. 发送日志
   for each peer
      sendAppendEntries()
      
10. 处理日志追加请求
    if (request.term < currentTerm)
       return false
    
    currentTerm = request.term
    resetElectionTimer()
    
    if (request.prevLogIndex >= 0 and log[request.prevLogIndex].term != request.prevLogTerm)
       return false
    
    if (request.entries is not empty)
    {
       for each entry in request.entries
          if (entry.term < currentTerm)
             continue
          if (entry.index < len(log) and log[entry.index].term != entry.term)
             log = log[:entry.index]
          if (entry.index >= len(log))
             log.append(entry)
    }
    
    if (request.leaderCommit > commitIndex)
    {
       commitIndex = min(request.leaderCommit, len(log) - 1)
       applyLogs()
    }
    
    return true

这是Raft算法的一个简单实现，其中包括处理请求投票请求、处理心跳、选主定时器超时、开始新一轮选举、发送投票请求、收到投票、成为领导者、发送日志、处理日志追加请求等步骤。实现起来比较复杂，需要考虑各种情况，但是这个伪代码可以帮助我们更好地理解Raft算法的实现。