基于.NET Standard的分布式自增ID算法--Snowflake代码实现

概述

上篇文章介绍了3种常见的Id生成算法，本篇主要介绍如何使用C#实现Snowflake。

基础字段

/// <summary>
/// 工作节点Id（长度为5位）
/// </summary>
public long WorkId{get;protected set;}/// <summary>
/// 机房Id（长度为5位）
/// </summary>
public long DataCenterId{get;protected set;}/// <summary>
/// 当前生成的Id
/// </summary>
public long CurrentId { get;protected set; }

基础方法

//获取当前时间的Unix时间戳
private long TimeGen()
{
return DateTimeOffset.UtcNow.ToUnixTimeMilliseconds();
}//生成新时间戳（一定比上次生成的时间戳大）
private long TilNextMillis(long lastTimestamp)
{
var timestamp = TimeGen();
while (timestamp <= lastTimestamp)
{
timestamp = TimeGen();
}
return timestamp;
}

Id生成核心方法

private const long TwEpoch = 1543765593681L;//2018-12-2 15:47:06 +00:00 private const int WorkerIdBits = 5;
private const int DatacenterIdBits = 5;
private const int SequenceBits = 12;
private const long MaxWorkerId = -1L ^ (-1L << WorkerIdBits);
private const long MaxDatacenterId = -1L ^ (-1L << DatacenterIdBits); private const int WorkerIdShift = SequenceBits;
private const int DatacenterIdShift = SequenceBits + WorkerIdBits;
private const int TimestampLeftShift = SequenceBits + WorkerIdBits + DatacenterIdBits;
private const long SequenceMask = -1L ^ (-1L << SequenceBits); private long _sequence = 0L;
private long _lastTimestamp = -1L; private readonly object _lock = new object(); public long NextId()
{
lock (_lock)
{
var timestamp = TimeGen();
if (timestamp < _lastTimestamp)
{
//TODO 是否可以考虑直接等待？
throw new Exception(
$"Clock moved backwards or wrapped around. Refusing to generate id for {_lastTimestamp - timestamp} ticks");
} if (_lastTimestamp == timestamp)
{
_sequence = (_sequence + 1) & SequenceMask;
if (_sequence == 0)
{
timestamp = TilNextMillis(_lastTimestamp);
}
}
else
{
_sequence = 0;
}
_lastTimestamp = timestamp;
CurrentId = ((timestamp - TwEpoch) << TimestampLeftShift) |
(DatacenterId << DatacenterIdShift) |
(WorkerId << WorkerIdShift) | _sequence; return CurrentId;
}
}完整实现、使用Demo以及benchmark测试请参见源代码：https://github.com/sampsonye/nice