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https://github.com/sija/ksuid.cr

Crystal implementation of K-Sortable Globally Unique IDs
https://github.com/sija/ksuid.cr

coordination crystal ksuid unique-id uuid

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Crystal implementation of K-Sortable Globally Unique IDs

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# ksuid.cr [![CI](https://github.com/Sija/ksuid.cr/actions/workflows/ci.yml/badge.svg)](https://github.com/Sija/ksuid.cr/actions/workflows/ci.yml) [![Releases](https://img.shields.io/github/release/Sija/ksuid.cr.svg)](https://github.com/Sija/ksuid.cr/releases) [![License](https://img.shields.io/github/license/Sija/ksuid.cr.svg)](https://github.com/Sija/ksuid.cr/blob/master/LICENSE)



This library implements the [K-Sortable Globally Unique IDs](https://github.com/segmentio/ksuid) from Segment.

The original readme for the Go version of KSUID does a great job of explaining

what they are and how they should be used, so it is excerpted here.



See also the article called [A Brief History of the UUID](https://segment.com/blog/a-brief-history-of-the-uuid/).



# What is a KSUID?



KSUID is for K-Sortable Unique IDentifier. It's a way to generate globally

unique IDs similar to [RFC 4122](https://tools.ietf.org/html/rfc4122) UUIDs,

but contain a time component so they can be "roughly" sorted by time of

creation. The remainder of the KSUID is randomly generated bytes.



# Why use KSUIDs?



Distributed systems often require unique IDs. There are numerous solutions

out there for doing this, so why KSUID?



## 1. Sortable by Timestamp



Unlike the more common choice of UUIDv4, KSUIDs contain a timestamp component

that allows them to be roughly sorted by generation time. This is obviously not

a strong guarantee as it depends on wall clocks, but is still incredibly useful

in practice.



## 2. No Coordination Required



[Snowflake IDs](https://blog.twitter.com/2010/announcing-snowflake) and

derivatives require coordination, which significantly increases the complexity

of implementation and creates operations overhead. While RFC 4122 UUIDv1s do

have a time component, there aren't enough bytes of randomness to provide

strong protections against duplicate ID generation.



KSUIDs use 128-bits of pseudorandom data, which provides a 64-times larger

number space than the 122-bits in the well-accepted RFC 4122 UUIDv4 standard.

The additional timestamp component drives down the extremely rare chance of

duplication to the point of near physical infeasibility, even assuming extreme

clock skew (> 24-hours) that would cause other severe anomalies.



## 3. Lexographically Sortable, Portable Representations



The binary and string representations are lexicographically sortable, which

allows them to be dropped into systems which do not natively support KSUIDs

and retain their k-sortable characteristics.



The string representation is that it is base62-encoded, so that they can "fit"

anywhere alphanumeric strings are accepted.



# How do they work?



KSUIDs are 20-bytes: a 32-bit unsigned integer UTC timestamp and a 128-bit

randomly generated payload. The timestamp uses big-endian encoding, to allow

lexicographic sorting. The timestamp epoch is adjusted to May 13th, 2014,

providing over 100 years of useful life starting at UNIX epoch + 14e8. The

payload uses a cryptographically-strong pseudorandom number generator.



The string representation is fixed at 27-characters encoded using a base62

encoding that also sorts lexicographically.



## Installation



Add this to your application's `shard.yml`:



```yaml

dependencies:

  ksuid:

    github: Sija/ksuid.cr

```



## Usage



```crystal

require "ksuid"

```



To generate a random KSUID for the present time, use:



```crystal

ksuid = KSUID.new

```



To generate a KSUID for a specific timestamp, use:



```crystal

ksuid = KSUID.new(time: time) # where *time* is a `Time` object

```



If you need to parse a KSUID from a string that you received, use the

conversion method:



```crystal

ksuid = KSUID.from(base62_string)

```



If you need to interpret a series of bytes that you received, use the

conversion method:



```crystal

ksuid = KSUID.from(bytes)

```



### JSON



```crystal

require "ksuid/json"



class Example

  include JSON::Serializable



  property id : KSUID

end



example = Example.from_json(%({"id": "aWgEPTl1tmebfsQzFP4bxwgy80V"}))

# => #



example.to_json

# => "{\"id\":\"aWgEPTl1tmebfsQzFP4bxwgy80V\"}"

```



### YAML



```crystal

require "ksuid/yaml"



class Example

  include YAML::Serializable



  property id : KSUID

end



example = Example.from_yaml(%(---\nid: aWgEPTl1tmebfsQzFP4bxwgy80V\n))

# => #



example.to_yaml

# => "---\nid: aWgEPTl1tmebfsQzFP4bxwgy80V\n"

```



## Contributing



1. Fork it ()

2. Create your feature branch (`git checkout -b my-new-feature`)

3. Commit your changes (`git commit -am 'Add some feature'`)

4. Push to the branch (`git push origin my-new-feature`)

5. Create a new Pull Request



## Contributors



- [@Sija](https://github.com/Sija) Sijawusz Pur Rahnama - creator, maintainer