Globally Unique ID Generator

This project is a ruby implementation of the Go Lang library found here: https://github.com/rs/xid

I've included the ReadMe from that project here (with some modifications for ruby).

Package xid is a globally unique id generator library, ready to be used safely directly in your server code.

Xid is using Mongo Object ID algorithm to generate globally unique ids with a different serialization (base64) to make it shorter when transported as a string: https://docs.mongodb.org/manual/reference/object-id/

• 4-byte value representing the seconds since the Unix epoch,
• 3-byte machine identifier,
• 2-byte process id, and
• 3-byte counter, starting with a random value.

The binary representation of the id is compatible with Mongo 12 bytes Object IDs. The string representation is using base32 hex (w/o padding) for better space efficiency when stored in that form (20 bytes). The hex variant of base32 is used to retain the sortable property of the id.

Xid doesn't use base64 because case sensitivity and the 2 non alphanum chars may be an issue when transported as a string between various systems. Base36 wasn't retained either because 1/ it's not standard 2/ the resulting size is not predictable (not bit aligned) and 3/ it would not remain sortable. To validate a base32 xid, expect a 20 chars long, all lowercase sequence of a to v letters and 0 to 9 numbers ([0-9a-v]{20}).

UUIDs are 16 bytes (128 bits) and 36 chars as string representation. Twitter Snowflake ids are 8 bytes (64 bits) but require machine/data-center configuration and/or central generator servers. xid stands in between with 12 bytes (96 bits) and a more compact URL-safe string representation (20 chars). No configuration or central generator server is required so it can be used directly in server's code.

Name	Binary Size	String Size	Features
UUID	16 bytes	36 chars	configuration free, not sortable
shortuuid	16 bytes	22 chars	configuration free, not sortable
Snowflake	8 bytes	up to 20 chars	needs machin/DC configuration, needs central server, sortable
MongoID	12 bytes	24 chars	configuration free, sortable
xid	12 bytes	20 chars	configuration free, sortable

Features:

• Size: 12 bytes (96 bits), smaller than UUID, larger than snowflake
• Base32 hex encoded by default (20 chars when transported as printable string, still sortable)
• Non configured, you don't need set a unique machine and/or data center id
• K-ordered
• Embedded time with 1 second precision
• Unicity guaranteed for 16,777,216 (24 bits) unique ids per second and per host/process

Best used with xlog's RequestIDHandler.

References:

• http://www.slideshare.net/davegardnerisme/unique-id-generation-in-distributed-systems
• https://en.wikipedia.org/wiki/Universally_unique_identifier
• https://blog.twitter.com/2010/announcing-snowflake

Install

    gem install ruby_xid

https://rubygems.org/gems/ruby_xid

Usage

guid = Xid.new
guid.to_s

# output:
"bnl5su800jo0po2ac17g"

# Generate next Xid
guid.next

# output:
"bnl5su800jo0po2ac18a"

guid = Xid.from_string("bnl5su800jo0po2ac17g")

Get xid embedded info:

guid.machine
guid.pid
guid.counter
guid.time

Development

Dependencies

Runtime: No external dependencies (uses only Ruby standard library)

Development dependencies:

• minitest - For running tests
• rake - For task automation (optional)
• benchmark-ips - For running comparative benchmarks (optional)
• bson - For comparing with MongoDB ObjectID (optional)

Install development dependencies:

gem install minitest rake
gem install benchmark-ips bson  # Optional, for benchmarks

Running Tests

Using Rake:

rake test

Or directly:

ruby -I lib test/test_ruby_xid.rb

The test suite includes:

• Uniqueness tests (1000 XIDs)
• String serialization and round-trip conversion
• Field extraction (time, machine, PID, counter)
• Go compatibility tests with reference test vectors
• Thread safety tests (100 threads × 100 XIDs)

Running Benchmarks

Simple benchmark (no external dependencies):

rake benchmark
# or
ruby simple_benchmark.rb

Full comparative benchmark (requires benchmark-ips and bson gems):

rake benchmark_full
# or
ruby -I lib benchmark.rb

Benchmarks measure:

• Xid.new - ID generation speed
• Xid.new.to_s - Generation and stringification
• from_string - Parsing XIDs from strings
• Field extraction - Accessing embedded data
• Comparison with BSON::ObjectId performance

Licenses

All source code is licensed under the MIT License.