sonyflake

README

Sonyflake

Sonyflake is a distributed unique ID generator inspired by Twitter's Snowflake.

Sonyflake focuses on lifetime and performance on many host/core environment. So it has a different bit assignment from Snowflake. A Sonyflake ID is composed of

39 bits for time in units of 10 msec
 8 bits for a sequence number
16 bits for a machine id

As a result, Sonyflake has the following advantages and disadvantages:

• The lifetime (174 years) is longer than that of Snowflake (69 years)
• It can work in more distributed machines (2^16) than Snowflake (2^10)
• It can generate 2^8 IDs per 10 msec at most in a single machine/thread (slower than Snowflake)

However, if you want more generation rate in a single host, you can easily run multiple Sonyflake ID generators concurrently using goroutines.

Installation

go get github.com/sony/sonyflake

Usage

The function New creates a new Sonyflake instance.

func New(st Settings) (*Sonyflake, error)

You can configure Sonyflake by the struct Settings:

type Settings struct {
	StartTime      time.Time
	MachineID      func() (uint16, error)
	CheckMachineID func(uint16) bool
}

• StartTime is the time since which the Sonyflake time is defined as the elapsed time. If StartTime is 0, the start time of the Sonyflake is set to "2014-09-01 00:00:00 +0000 UTC". If StartTime is ahead of the current time, Sonyflake is not created.

• MachineID returns the unique ID of the Sonyflake instance. If MachineID returns an error, Sonyflake is not created. If MachineID is nil, default MachineID is used. Default MachineID returns the lower 16 bits of the private IP address.

• CheckMachineID validates the uniqueness of the machine ID. If CheckMachineID returns false, Sonyflake is not created. If CheckMachineID is nil, no validation is done.

In order to get a new unique ID, you just have to call the method NextID.

func (sf *Sonyflake) NextID() (uint64, error)

NextID can continue to generate IDs for about 174 years from StartTime. But after the Sonyflake time is over the limit, NextID returns an error.

Note: Sonyflake currently does not use the most significant bit of IDs, so you can convert Sonyflake IDs from uint64 to int64 safely.

AWS VPC and Docker

The awsutil package provides the function AmazonEC2MachineID that returns the lower 16-bit private IP address of the Amazon EC2 instance. It also works correctly on Docker by retrieving instance metadata.

AWS VPC is assigned a single CIDR with a netmask between /28 and /16. So if each EC2 instance has a unique private IP address in AWS VPC, the lower 16 bits of the address is also unique. In this common case, you can use AmazonEC2MachineID as Settings.MachineID.

See example that runs Sonyflake on AWS Elastic Beanstalk.

License

The MIT License (MIT)

See LICENSE for details.

Documentation

Overview

Package sonyflake implements Sonyflake, a distributed unique ID generator inspired by Twitter's Snowflake.

A Sonyflake ID is composed of

39 bits for time in units of 10 msec
 8 bits for a sequence number
16 bits for a machine id

Index

• Constants
• Variables
• func Decompose(id uint64) map[string]uint64
• func ElapsedTime(id uint64) time.Duration
• func MachineID(id uint64) uint64
• func SequenceNumber(id uint64) uint64
• type Settings
• type Sonyflake
  • func New(st Settings) (*Sonyflake, error)
  • func NewSonyflake(st Settings) *Sonyflake
  • func (sf *Sonyflake) NextID() (uint64, error)

Constants

const (
	BitLenTime      = 39                               // bit length of time
	BitLenSequence  = 8                                // bit length of sequence number
	BitLenMachineID = 63 - BitLenTime - BitLenSequence // bit length of machine id
)

These constants are the bit lengths of Sonyflake ID parts.

Variables

var (
	ErrStartTimeAhead   = errors.New("start time is ahead of now")
	ErrNoPrivateAddress = errors.New("no private ip address")
	ErrOverTimeLimit    = errors.New("over the time limit")
	ErrInvalidMachineID = errors.New("invalid machine id")
)

Functions

func Decompose

func Decompose(id uint64) map[string]uint64

Decompose returns a set of Sonyflake ID parts.

func ElapsedTime

func ElapsedTime(id uint64) time.Duration

ElapsedTime returns the elapsed time when the given Sonyflake ID was generated.

func MachineID

func MachineID(id uint64) uint64

MachineID returns the machine ID of a Sonyflake ID.

func SequenceNumber

func SequenceNumber(id uint64) uint64

SequenceNumber returns the sequence number of a Sonyflake ID.

Types

type Settings

type Settings struct {
	StartTime      time.Time
	MachineID      func() (uint16, error)
	CheckMachineID func(uint16) bool
}

Settings configures Sonyflake:

StartTime is the time since which the Sonyflake time is defined as the elapsed time. If StartTime is 0, the start time of the Sonyflake is set to "2014-09-01 00:00:00 +0000 UTC". If StartTime is ahead of the current time, Sonyflake is not created.

MachineID returns the unique ID of the Sonyflake instance. If MachineID returns an error, Sonyflake is not created. If MachineID is nil, default MachineID is used. Default MachineID returns the lower 16 bits of the private IP address.

CheckMachineID validates the uniqueness of the machine ID. If CheckMachineID returns false, Sonyflake is not created. If CheckMachineID is nil, no validation is done.

type Sonyflake

type Sonyflake struct {
	// contains filtered or unexported fields
}

Sonyflake is a distributed unique ID generator.

func New

func New(st Settings) (*Sonyflake, error)

New returns a new Sonyflake configured with the given Settings. New returns an error in the following cases: - Settings.StartTime is ahead of the current time. - Settings.MachineID returns an error. - Settings.CheckMachineID returns false.

func NewSonyflake

func NewSonyflake(st Settings) *Sonyflake

NewSonyflake returns a new Sonyflake configured with the given Settings. NewSonyflake returns nil in the following cases: - Settings.StartTime is ahead of the current time. - Settings.MachineID returns an error. - Settings.CheckMachineID returns false.

func (*Sonyflake) NextID

func (sf *Sonyflake) NextID() (uint64, error)

NextID generates a next unique ID. After the Sonyflake time overflows, NextID returns an error.