README.md (6310B)
1 # Globally Unique ID Generator 2 3 [](https://godoc.org/github.com/rs/xid) [](https://raw.githubusercontent.com/rs/xid/master/LICENSE) [](https://travis-ci.org/rs/xid) [](http://gocover.io/github.com/rs/xid) 4 5 Package xid is a globally unique id generator library, ready to safely be used directly in your server code. 6 7 Xid uses the Mongo Object ID algorithm to generate globally unique ids with a different serialization (base64) to make it shorter when transported as a string: 8 https://docs.mongodb.org/manual/reference/object-id/ 9 10 - 4-byte value representing the seconds since the Unix epoch, 11 - 3-byte machine identifier, 12 - 2-byte process id, and 13 - 3-byte counter, starting with a random value. 14 15 The binary representation of the id is compatible with Mongo 12 bytes Object IDs. 16 The string representation is using base32 hex (w/o padding) for better space efficiency 17 when stored in that form (20 bytes). The hex variant of base32 is used to retain the 18 sortable property of the id. 19 20 Xid doesn't use base64 because case sensitivity and the 2 non alphanum chars may be an 21 issue when transported as a string between various systems. Base36 wasn't retained either 22 because 1/ it's not standard 2/ the resulting size is not predictable (not bit aligned) 23 and 3/ it would not remain sortable. To validate a base32 `xid`, expect a 20 chars long, 24 all lowercase sequence of `a` to `v` letters and `0` to `9` numbers (`[0-9a-v]{20}`). 25 26 UUIDs are 16 bytes (128 bits) and 36 chars as string representation. Twitter Snowflake 27 ids are 8 bytes (64 bits) but require machine/data-center configuration and/or central 28 generator servers. xid stands in between with 12 bytes (96 bits) and a more compact 29 URL-safe string representation (20 chars). No configuration or central generator server 30 is required so it can be used directly in server's code. 31 32 | Name | Binary Size | String Size | Features 33 |-------------|-------------|----------------|---------------- 34 | [UUID] | 16 bytes | 36 chars | configuration free, not sortable 35 | [shortuuid] | 16 bytes | 22 chars | configuration free, not sortable 36 | [Snowflake] | 8 bytes | up to 20 chars | needs machine/DC configuration, needs central server, sortable 37 | [MongoID] | 12 bytes | 24 chars | configuration free, sortable 38 | xid | 12 bytes | 20 chars | configuration free, sortable 39 40 [UUID]: https://en.wikipedia.org/wiki/Universally_unique_identifier 41 [shortuuid]: https://github.com/stochastic-technologies/shortuuid 42 [Snowflake]: https://blog.twitter.com/2010/announcing-snowflake 43 [MongoID]: https://docs.mongodb.org/manual/reference/object-id/ 44 45 Features: 46 47 - Size: 12 bytes (96 bits), smaller than UUID, larger than snowflake 48 - Base32 hex encoded by default (20 chars when transported as printable string, still sortable) 49 - Non configured, you don't need set a unique machine and/or data center id 50 - K-ordered 51 - Embedded time with 1 second precision 52 - Unicity guaranteed for 16,777,216 (24 bits) unique ids per second and per host/process 53 - Lock-free (i.e.: unlike UUIDv1 and v2) 54 55 Best used with [zerolog](https://github.com/rs/zerolog)'s 56 [RequestIDHandler](https://godoc.org/github.com/rs/zerolog/hlog#RequestIDHandler). 57 58 Notes: 59 60 - Xid is dependent on the system time, a monotonic counter and so is not cryptographically secure. If unpredictability of IDs is important, you should not use Xids. It is worth noting that most other UUID-like implementations are also not cryptographically secure. You should use libraries that rely on cryptographically secure sources (like /dev/urandom on unix, crypto/rand in golang), if you want a truly random ID generator. 61 62 References: 63 64 - http://www.slideshare.net/davegardnerisme/unique-id-generation-in-distributed-systems 65 - https://en.wikipedia.org/wiki/Universally_unique_identifier 66 - https://blog.twitter.com/2010/announcing-snowflake 67 - Python port by [Graham Abbott](https://github.com/graham): https://github.com/graham/python_xid 68 - Scala port by [Egor Kolotaev](https://github.com/kolotaev): https://github.com/kolotaev/ride 69 - Rust port by [Jérôme Renard](https://github.com/jeromer/): https://github.com/jeromer/libxid 70 - Ruby port by [Valar](https://github.com/valarpirai/): https://github.com/valarpirai/ruby_xid 71 - Java port by [0xShamil](https://github.com/0xShamil/): https://github.com/0xShamil/java-xid 72 - Dart port by [Peter Bwire](https://github.com/pitabwire): https://pub.dev/packages/xid 73 - PostgreSQL port by [Rasmus Holm](https://github.com/crholm): https://github.com/modfin/pg-xid 74 - Swift port by [Uditha Atukorala](https://github.com/uditha-atukorala): https://github.com/uditha-atukorala/swift-xid 75 - C++ port by [Uditha Atukorala](https://github.com/uditha-atukorala): https://github.com/uditha-atukorala/libxid 76 77 ## Install 78 79 go get github.com/rs/xid 80 81 ## Usage 82 83 ```go 84 guid := xid.New() 85 86 println(guid.String()) 87 // Output: 9m4e2mr0ui3e8a215n4g 88 ``` 89 90 Get `xid` embedded info: 91 92 ```go 93 guid.Machine() 94 guid.Pid() 95 guid.Time() 96 guid.Counter() 97 ``` 98 99 ## Benchmark 100 101 Benchmark against Go [Maxim Bublis](https://github.com/satori)'s [UUID](https://github.com/satori/go.uuid). 102 103 ``` 104 BenchmarkXID 20000000 91.1 ns/op 32 B/op 1 allocs/op 105 BenchmarkXID-2 20000000 55.9 ns/op 32 B/op 1 allocs/op 106 BenchmarkXID-4 50000000 32.3 ns/op 32 B/op 1 allocs/op 107 BenchmarkUUIDv1 10000000 204 ns/op 48 B/op 1 allocs/op 108 BenchmarkUUIDv1-2 10000000 160 ns/op 48 B/op 1 allocs/op 109 BenchmarkUUIDv1-4 10000000 195 ns/op 48 B/op 1 allocs/op 110 BenchmarkUUIDv4 1000000 1503 ns/op 64 B/op 2 allocs/op 111 BenchmarkUUIDv4-2 1000000 1427 ns/op 64 B/op 2 allocs/op 112 BenchmarkUUIDv4-4 1000000 1452 ns/op 64 B/op 2 allocs/op 113 ``` 114 115 Note: UUIDv1 requires a global lock, hence the performance degradation as we add more CPUs. 116 117 ## Licenses 118 119 All source code is licensed under the [MIT License](https://raw.github.com/rs/xid/master/LICENSE).