Have ideas to improve npm?Join in the discussion! »

    flake-idgen
    DefinitelyTyped icon, indicating that this package has TypeScript declarations provided by the separate @types/flake-idgen package

    1.4.0 • Public • Published

    Flake ID Generator

    Build Status npm version npm downloads Code Climate Coverage Status GitHub issues GitHub license

    Flake ID generator yields k-ordered, conflict-free ids in a distributed environment.

    Installation

    $ npm install --save flake-idgen ⏎

    Flake Numbers Format

    The Flake ID is made up of: timestamp, datacenter, worker and counter. Examples in the following table:

    +-------------+------------+--------+---------+--------------------+
    |  Timestamp  | Datacenter | Worker | Counter | Flake ID           |
    +-------------+------------+--------+---------+--------------------+
    | 0x8c20543b0 |   00000b   | 00000b |  0x000  | 0x02308150ec000000 |
    +-------------+------------+--------+---------+--------------------+
    | 0x8c20543b1 |   00000b   | 00000b |  0x000  | 0x02308150ec400000 |
    +-------------+------------+--------+---------+--------------------+
    | 0x8c20543b1 |   00000b   | 00000b |  0x001  | 0x02308150ec400001 |
    +-------------+------------+--------+---------+--------------------+
    | 0x8c20543b1 |   00000b   | 00000b |  0x002  | 0x02308150ec400002 |
    +-------------+------------+--------+---------+--------------------+
    | 0x8c20543b1 |   00000b   | 00000b |  0x003  | 0x02308150ec400003 |
    +-------------+------------+--------+---------+--------------------+
    | 0x8c20c0335 |   00011b   | 00001b |  0x000  | 0x02308300cd461000 |
    +-------------+------------+--------+---------+--------------------+
    | 0x8c20c0335 |   00011b   | 00001b |  0x001  | 0x02308300cd461001 |
    +-------------+------------+--------+---------+--------------------+
    

    As you can see, each Flake ID is 64 bits long, consisting of:

    • timestamp, a 42 bit long number of milliseconds elapsed since 1 January 1970 00:00:00 UTC
    • datacenter, a 5 bit long datacenter identifier. It can take up to 32 unique values (including 0)
    • worker, a 5 bit long worker identifier. It can take up to 32 unique values (including 0)
    • counter, a 12 bit long counter of ids in the same millisecond. It can take up to 4096 unique values.

    Breakdown of bits for an id e.g. 5828128208445124608 (counter is 0, datacenter is 7 and worker 3) is as follows:

     010100001110000110101011101110100001000111 00111 00011 000000000000
                                                           |------------| 12 bit counter
                                                     |-----|               5 bit worker
                                               |-----|                     5 bit datacenter
                                               |----- -----|              10 bit generator identifier
    |------------------------------------------|                          42 bit timestamp
    

    Note that composition of datacenter id and worker id makes 1024 unique generator identifiers. By modifying datacenter and worker id we can get up to 1024 id generators on a single machine (e.g. each running in a separate process) or have 1024 machines with a single id generator on each. It is also possible to provide a single 10 bit long identifier (up to 1024 values). That id is internally split into datacenter (the most significant 5 bits) and worker (the least significant 5 bits).

    Usage

    Flake ID Generator returns 8 byte long node Buffer objects with its bytes representing 64 bit long id. Note that the number is stored in Big Endian format i.e. the most significant byte of the number is stored in the smallest address given and the least significant byte is stored in the largest.

    Flake id generator instance has one method next(cb) returning generated id (if a callback function is not provided) or calling provided callback function with two arguments: error and generated id.

    The following example uses next with no callback function:

    var FlakeId = require('flake-idgen');
    var flakeIdGen = new FlakeId();
     
    console.log(flakeIdGen.next());
    console.log(flakeIdGen.next());
    console.log(flakeIdGen.next());

    It would give something like:

    <Buffer 50 dd d5 99 01 c0 00 00>
    <Buffer 50 dd d5 99 02 80 00 00>
    <Buffer 50 dd d5 99 02 80 00 01>
    

    The following example uses next with callback function:

    var FlakeId = require('flake-idgen');
    var flakeIdGen = new FlakeId();
     
    flakeIdGen.next(function (err, id) {
         console.info(id);
    })
     
    flakeIdGen.next(function (err, id) {
         console.info(id);
    })

    It would give something like:

    <Buffer 50 dd d6 49 ef c0 00 00>
    <Buffer 50 dd d6 49 f0 00 00 00>
    

    Counter overflow

    Flake ID Generator can generate up to 4096 unique identifiers within a millisecond. When generator tries to generate more than 4096 identifiers within a millisecond, the following things will happen:

    • When using next() without a callback function, an error is thrown.
    • When using next(cb) with a callback function, the callback function is called in the following millisecond without any error.

    Additional generator setup parameters

    Flake Id generator constructor takes optional parameter (generator configuration options) with the following properties:

    • datacenter (5 bit) - datacenter identifier. It can have values from 0 to 31.
    • worker (5 bit) - worker identifier. It can have values from 0 to 31.
    • id (10 bit) - generator identifier. It can have values from 0 to 1023. It can be provided instead of datacenter and worker identifiers.
    • epoch - number used to reduce value of a generated timestamp. Note that this number should not exceed number of milliseconds elapsed since 1 January 1970 00:00:00 UTC. It can be used to generate smaller ids.

    Example of using datacenter and worker identifiers:

    var FlakeId = require('flake-idgen')
     
    var flakeIdGen1 = new FlakeId();
    var flakeIdGen2 = new FlakeId({ datacenter: 9, worker: 7 });
     
    console.info(flakeIdGen1.next());
    console.info(flakeIdGen2.next());

    It would give something like:

    <Buffer 50 dd da 8f 43 40 00 00>
    <Buffer 50 dd da 8f 43 d2 70 00>
    

    Example of using epoch parameter:

    var FlakeId = require('flake-idgen')
     
    var flakeIdGen1 = new FlakeId();
    var flakeIdGen2 = new FlakeId({ epoch: 1300000000000 });
     
    console.info(flakeIdGen1.next());
    console.info(flakeIdGen2.next());

    It would give something like:

    <Buffer 50 dd db 00 d1 c0 00 00>
    <Buffer 05 32 58 8e d2 40 00 00>
    

    Properties

    Flake Id generator has some properties that can be read from a generator instance:

    • datacenter - returns worker number used for generator creation; otherwise it returns undefined value.
    • worker - returns worker number used for generator creation; otherwise it returns undefined value.
    • id - returns worker identifier number used for generator creation or combines its value from datacenter and worker numbers. Identifier is always available and it is defaulted to zero.

    Flake Id generator instantiated without any parameter gets datacenter, worker and id values defaulted to zeros.

    var FlakeId = require('flake-idgen')
     
    var flakeIdGen1 = new FlakeId({ id: 100 });
    var flakeIdGen2 = new FlakeId({ datacenter: 9, worker: 7 });
    var flakeIdGen3 = new FlakeId();
     
    console.info(flakeIdGen1.id);           // 100
    console.info(flakeIdGen1.datacenter);   // undefined
    console.info(flakeIdGen1.worker);       // undefined
     
    console.info(flakeIdGen2.datacenter);   // 9
    console.info(flakeIdGen2.worker);       // 7
    console.info(flakeIdGen2.id);           // 259
     
    console.info(flakeIdGen3.datacenter);   // 0
    console.info(flakeIdGen3.worker);       // 0
    console.info(flakeIdGen3.id);           // 0

    It would give something like:

    100
    undefined
    undefined
     
    9
    7
    295
     
    0
    0
    0

    Clock moving backward

    From time to time Node.js clock may move backward. In most cases it is only a few millisecond. However, as the generator relies on current timestamp, it won't be able to generate conflict-free identifiers (i.e. without duplicates) until the clock catches up with the last timestamp value. In case of clock move backward the following things will happen:

    • When using next() without a callback function, an error is thrown.
    • When using next(cb) with a callback function, the callback function is called with a new identifier generated once the clock catches up with the last timestamp.

    Formatting

    Flake Id generator returns node Buffer representing 64-bit number for the sake of future extensions or returned buffer modifications. Node Buffer can also be very easily converted to string format. There is a NPM biguint-format module which provides Buffer to string conversion functionality e.g.

    var intformat = require('biguint-format')
        , FlakeId = require('flake-idgen')
     
    var flakeIdGen1 = new FlakeId();
    var flakeIdGen2 = new FlakeId({ epoch: 1300000000000 });
     
    console.info(intformat(flakeIdGen1.next(), 'dec'));
    console.info(intformat(flakeIdGen1.next(), 'hex', { prefix: '0x' }));
     
    console.info(intformat(flakeIdGen2.next(), 'dec'));
    console.info(intformat(flakeIdGen2.next(), 'hex', { prefix: '0x' }));

    It would give something like:

    5827056208820830208 // flakeIdGen1 decimal format
    0x50dddcbfb5c00001  // flakeIdGen1 hex format
     
    374461008833413120 // flakeIdGen2 decimal format
    0x5325a4db6000002  // flakeIdGen2 hex format

    Generated id could also be converted to binary string format, split into 4 digit groups of 0's and 1's e.g.

    var intformat = require('biguint-format')
        , idGen = new (require('flake-idgen'))
     
    for (var i = 0; i < 5; i++) {
        console.info(intformat(idGen.next(), 'bin', { groupsize: 4 }));
    };

    It would give something like:

    0101 0000 1101 1111 1011 0110 0001 0101 1100 0001 0100 0000 0000 0000 0000 0000 // 0x50 df b6 15 c1 40 00 00
    0101 0000 1101 1111 1011 0110 0001 0101 1100 0101 0000 0000 0000 0000 0000 0000 // 0x50 df b6 15 c5 00 00 00
    0101 0000 1101 1111 1011 0110 0001 0101 1100 0101 0000 0000 0000 0000 0000 0001 // 0x50 df b6 15 c5 00 00 01
    0101 0000 1101 1111 1011 0110 0001 0101 1100 0101 0100 0000 0000 0000 0000 0000 // 0x50 df b6 15 c5 40 00 00
    0101 0000 1101 1111 1011 0110 0001 0101 1100 0101 0100 0000 0000 0000 0000 0001 // 0x50 df b6 15 c5 40 00 01

    Author

    Written by Tom Pawlak - Blog

    License

    Copyright (c) 2014 Tom Pawlak

    MIT License : https://blog.abelotech.com/mit-license/

    Install

    npm i flake-idgen

    DownloadsWeekly Downloads

    8,146

    Version

    1.4.0

    License

    none

    Unpacked Size

    22.1 kB

    Total Files

    9

    Last publish

    Collaborators

    • avatar