Introduction

Snowflake is a service used to generate unique IDs for objects within Twitter (Tweets, Direct Messages, Users, Collections, Lists etc.). These IDs are unique 64-bit unsigned integers, which are based on time, instead of being sequential. The full ID is composed of a timestamp, a worker number, and a sequence number.
By default, 64-bit unsigned integers will generate an Id whose length is 19, but sometimes it may be too long, some customers need an Id whose length is 16.
In this article, I will show how can we adapt to generate an Id whose length is 16.

How to Do This?

The full ID is composed of a 41 bit timestamp, 10 bit worker number, and 12 bit sequence number.
We can reduce the bit count of those components to finish this work.
Here is a sample that we can follow.
  1. public class IdGenerator
  2. {
  3. public const long Twepoch = 1288834974000L;
  5. // change from 5 to 3
  6. private const int WorkerIdBits = 3;
  8. // change from 5 to 2
  9. private const int DatacenterIdBits = 2;
  11. // change from 12 to 8
  12. private const int SequenceBits = 8;
  14. private const long MaxWorkerId = -1L ^ (-1L << WorkerIdBits);
  16. private const long MaxDatacenterId = -1L ^ (-1L << DatacenterIdBits);
  18. private const long SequenceMask = -1L ^ (-1L << SequenceBits);
  20. private const int WorkerIdShift = SequenceBits;
  22. private const int DatacenterIdShift = SequenceBits + WorkerIdBits;
  24. public const int TimestampLeftShift = SequenceBits + WorkerIdBits + DatacenterIdBits;
  26. private long _sequence = 0L;
  27. private long _lastTimestamp = -1L;
  29. public long WorkerId { get; protected set; }
  31. public long DatacenterId { get; protected set; }
  33. public long Sequence
  34. {
  35. get { return _sequence; }
  36. internal set { _sequence = value; }
  37. }
  39. public IdGenerator(long workerId, long datacenterId, long sequence = 0L)
  40. {
  41. if (workerId > MaxWorkerId || workerId < 0)
  42. {
  43. throw new ArgumentException($"worker Id must greater than or equal 0 and less than or equal {MaxWorkerId}");
  44. }
  46. if (datacenterId > MaxDatacenterId || datacenterId < 0)
  47. {
  48. throw new ArgumentException($"datacenter Id must greater than or equal 0 and less than or equal {MaxDatacenterId}");
  49. }
  51. WorkerId = workerId;
  52. DatacenterId = datacenterId;
  53. _sequence = sequence;
  54. }
  56. private readonly object _lock = new object();
  58. public long NextId()
  59. {
  60. lock (_lock)
  61. {
  62. var timestamp = TimeGen();
  63. if (timestamp < _lastTimestamp)
  64. {
  65. throw new Exception($"timestamp error");
  66. }
  68. if (_lastTimestamp == timestamp)
  69. {
  70. _sequence = (_sequence + 1) & SequenceMask;
  72. if (_sequence == 0)
  73. {
  74. timestamp = TilNextMillis(_lastTimestamp);
  75. }
  76. }
  77. else
  78. {
  79. _sequence = 0;
  80. }
  82. _lastTimestamp = timestamp;
  83. return ((timestamp - Twepoch) << TimestampLeftShift) | (DatacenterId << DatacenterIdShift) | (WorkerId << WorkerIdShift) | _sequence;
  84. }
  85. }
  87. private long TilNextMillis(long lastTimestamp)
  88. {
  89. var timestamp = TimeGen();
  90. while (timestamp <= lastTimestamp)
  91. {
  92. timestamp = TimeGen();
  93. }
  95. return timestamp;
  96. }
  98. private long TimeGen()
  99. {
  100. return DateTimeOffset.UtcNow.ToUnixTimeMilliseconds();
  101. }
  102. }
As you can see, the above code reduces the bit count of worker number and sequence number.
The next step is to use this IdGenerator.
  1. static void Main(string[] args)
  2. {
  3. // keep the generator singleton
  4. var generator = new IdGenerator(0, 0);
  6. System.Threading.Tasks.Parallel.For(0, 20, x =>
  7. {
  8. Console.WriteLine(generator.NextId().ToString());
  9. });
  11. Console.WriteLine("Hello World!");
  12. Console.ReadKey();
  13. }
Here is the result of it.
NOTE
We should keep the generator qas a singleton, it means that we should only create the generator once. If not, it may generate some duplicate Ids.

Summary

This article showed you a simple solution of how to generate a snowflake id whose length is 16.
By the way, you can adjust the bit count to adapt your work.
I hope this will help you!