1[![Build status][buildimage]][build] [![Coverage][codecovimage]][codecov] [![GoReportCard][cardimage]][card] [![API documentation][docsimage]][docs] 2 3# Generator of unique non-sequential short Ids 4 5The package `shortid`enables the generation of short, fully unique, 6non-sequential and by default URL friendly Ids at a rate of hundreds of thousand per second. It 7guarantees uniqueness during the time period until 2050! 8 9The package is heavily inspired by the node.js [shortid][nodeshortid] library (see more detail below). 10 11The easiest way to start generating Ids is: 12 13 fmt.Printf(shortid.Generate()) 14 fmt.Printf(shortid.Generate()) 15 16The recommended one is to initialise and reuse a generator specific to a given worker: 17 18 sid, err := shortid.New(1, shortid.DefaultABC, 2342) 19 20 // then either: 21 fmt.Printf(sid.Generate()) 22 fmt.Printf(sid.Generate()) 23 24 // or: 25 shortid.SetDefault(sid) 26 // followed by: 27 fmt.Printf(shortid.Generate()) 28 fmt.Printf(shortid.Generate()) 29 30 31### Id Length 32 33The standard Id length is 9 symbols when generated at a rate of 1 Id per millisecond, 34occasionally it reaches 11 (at the rate of a few thousand Ids per millisecond) and very-very 35rarely it can go beyond that during continuous generation at full throttle on high-performant 36hardware. A test generating 500k Ids at full throttle on conventional hardware generated the 37following Ids at the head and the tail (length > 9 is expected for this test): 38 39 -NDveu-9Q 40 iNove6iQ9J 41 NVDve6-9Q 42 VVDvc6i99J 43 NVovc6-QQy 44 VVoveui9QC 45 ... 46 tFmGc6iQQs 47 KpTvcui99k 48 KFTGcuiQ9p 49 KFmGeu-Q9O 50 tFTvcu-QQt 51 tpTveu-99u 52 53### Life span 54 55The package guarantees the generation of unique Ids with no collisions for 34 years 56(1/1/2016-1/1/2050) using the same worker Id within a single (although can be concurrent) 57application provided application restarts take longer than 1 millisecond. The package supports 58up to 32 workers all providing unique sequences from each other. 59 60### Implementation details 61 62Although heavily inspired by the node.js [shortid][nodeshortid] library this is 63not just a Go port. This implementation 64 65* is safe to concurrency (test included); 66* does not require any yearly version/epoch resets (test included); 67* provides stable Id size over a the whole range of operation at the rate of 1ms (test included); 68* guarantees no collisions: due to guaranteed fixed size of Ids between milliseconds and because 69multiple requests within the same ms lead to longer Ids with the prefix unique to the ms (tests 70included); 71* supports 32 instead of 16 workers (test included) 72 73The algorithm uses less randomness than the original node.js implementation, which permits to extend 74the life span as well as reduce and guarantee the length. In general terms, each Id has the 75following 3 pieces of information encoded: the millisecond since epoch (first 8 symbols, epoch: 761/1/2016), the worker Id (9th symbol), the running concurrent counter within the millisecond (only 77if required, spanning over all remaining symbols). 78 79The element of randomness per symbol is 1/2 for the worker and the millisecond data and 0 for the 80counter. The original algorithm of the node.js library uses 1/4 throughout. Here 0 means no 81randomness, i.e. every value is encoded using a 64-base alphabet directly; 1/2 means one of two 82matching symbols of the supplied alphabet is used randomly, 1/4 one of four matching symbols. All 83methods accepting the parameters that govern the randomness are exported and can be used to directly 84implement an algorithm with e.g. more randomness, but with longer Ids and shorter life spans. 85 86### License and copyright 87 88 Copyright (c) 2016. Oleg Sklyar and teris.io. MIT license applies. All rights reserved. 89 90**[Original algorithm][nodeshortid]:** Copyright (c) 2015 Dylan Greene, contributors. The same MIT 91license applies. Many thanks to Dylan for putting together the original node.js library, which 92inspired this "port": 93 94**Seed computation:** based on The Central Randomizer 1.3. Copyright (c) 1997 Paul Houle (houle@msc.cornell.edu) 95 96[go]: https://golang.org 97[nodeshortid]: https://github.com/dylang/shortid 98 99[build]: https://travis-ci.org/teris-io/shortid 100[buildimage]: https://travis-ci.org/teris-io/shortid.svg?branch=master 101 102[codecov]: https://codecov.io/github/teris-io/shortid?branch=master 103[codecovimage]: https://codecov.io/github/teris-io/shortid/coverage.svg?branch=master 104 105[card]: http://goreportcard.com/report/teris-io/shortid 106[cardimage]: https://goreportcard.com/badge/github.com/teris-io/shortid 107 108[docs]: https://godoc.org/github.com/teris-io/shortid 109[docsimage]: http://img.shields.io/badge/godoc-reference-blue.svg?style=flat 110