jstepien/flake

Decentralized, k-ordered unique IDs in Clojure

Flake

Decentralized, k-ordered unique ID generator.

This is a Clojure implementation of Boundary's Erlang Flake ID service.

Installation

flake is available via Clojars:

[flake "0.2.0"]

Usage

New flake IDs can be generated with the generate fn from flake's core namespace.

Note that in order to prevent generation of duplicate IDs, init! should be called prior to generating IDs for the first time to prevent potential duplicate IDs.

For example:

=> (require '[flake.core :as flake])
=> (flake/init!)
=> (take 3 (repeatedly flake/generate))
(25978563106299135585558915252224N
 25978563106299135585558915252225N
 25978563106299135585558915252226N)

Here we have generated three BigIntegers which are flake IDs. Note how they are ordered.

It may be desirable to encode these IDs in a shorter representation, such as Base62. The utils namespace provides an encoder:

=> (require '[flake.utils :as utils])
=> (utils/base62-encode (flake/generate))
"8mwFA958SJ2CZVu9nk"

Exceptional cases

When generating flakes, if system time flows backwards then an IllegalStateException will be thrown. In the extremely unlikely event that you generate more than 65,535 flakes on one machine in a millisecond (65 million flakes/second) then an IllegalArgumentException will be thrown as the flake sequence id (of type short) overflows.