Globally Unique ID Generator

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 (bast64) 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 URL safe base64 for better space efficiency when stored in that form (16 bytes).

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 (16 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	16 chars	configuration free, sortable

Features:

• Size: 12 bytes (96 bits), smaller than UUID, larger than snowflake
• Base64 URL safe encoded by default (16 chars when transported as printable string)
• 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

go get github.com/rs/xid

Usage

guid := xid.New()

println(guid.String())
// Output: TYjhW2D0huQoQS3J

Get xid embedded info:

guid.Machine()
guid.Pid()
guid.Time()
guid.Counter()

Licenses

All source code is licensed under the MIT License.