sequencer

Documentation

Overview

Package sequencer provides sequences based on monotonic time

Time

The sequncer package provides sequences based on the monotonic time which represents the absolute elapsed wall-clock time since some arbitrary, fixed point in the past. It isn't affected by changes in the system time-of-day clock.

Time - Consequences

Since the monotonic time needs extra calculation steps when it is compared to regular system time, it also consumes an extra time while generating sequences.

NOTE: According to the documentation of Go language [time package](https://golang.org/pkg/time/), on some systems the monotonic clock will stop if the computer goes to sleep. On such a system, t.Sub(u) may not accurately reflect the actual time that passed between t and u which will result with incorrect sequences.

Byte Sizes

The total byte size is fixed to 16 bytes for any sequencer. And at least one byte is reserved to nodes. The package comes with three pre-configured sequencers and Sequencer interface to allow new sequencers.

Byte Sizes - Defaults

The package comes with pre-configured byte sizes for the Nanosecond, Millisecond and Second sequencers. And it does not allow you to adjust current sizes unless you create another sequencer. The defaults are adjusted the time and sequence byte sizes depending on general needs and to increase compatibility between projects.

The current byte sizes:

Second:      16 B =>  6 B (seconds)      + 6 B (counter) + 4 B (node)
Millisecond: 16 B =>  8 B (milliseconds) + 4 B (counter) + 4 B (node)
Nanosecond:  16 B => 11 B (nanoseconds)  + 2 B (counter) + 3 B (node)

Byte Sizes - Consequences

Although a strict byte size is limiting the space for nodes and sequences, 16 B gives enough flexibility for time, counter and nodes. In next 50 years, it could be necessary to provide a strategy to upgrade byte size to 32 B.

Index

• type Sequence
  • func NewMillisecond() *Sequence
  • func NewNanosecond() *Sequence
  • func NewSecond() *Sequence
  • func (s *Sequence) Max() uint64
  • func (s *Sequence) MaxTime() uint64
  • func (s *Sequence) Next() (uint64, uint64)
• type Sequencer

Types

type Sequence

type Sequence struct {
	sync.Mutex
	// contains filtered or unexported fields
}

Sequence is an implementation of sequencer

func NewMillisecond

func NewMillisecond() *Sequence

NewMillisecond returns the preconfigured millisecond sequencer

func NewNanosecond

func NewNanosecond() *Sequence

NewNanosecond returns the preconfigured nanosecond sequencer

func NewSecond

func NewSecond() *Sequence

NewSecond returns the preconfigured second sequencer

func (*Sequence) Max

func (s *Sequence) Max() uint64

Max returns the maximum possible sequence value

func (*Sequence) MaxTime

func (s *Sequence) MaxTime() uint64

MaxTime returns the maximum possible time sequence value

func (*Sequence) Next

func (s *Sequence) Next() (uint64, uint64)

Next returns the next sequence

type Sequencer

type Sequencer interface {
	// Max returns the maximum possible sequence value for a given time
	Max() uint64
	// MaxTime returns the maximum possible time sequence value
	MaxTime() uint64
	// Now returns the current monotonic time
	Next() (uint64, uint64)
}

Sequencer is a generic behavior for the sequence generators