consistent

Documentation

Overview

An implementation of Consistent Hashing and Consistent Hashing With Bounded Loads.

https://en.wikipedia.org/wiki/Consistent_hashing

https://research.googleblog.com/2017/04/consistent-hashing-with-bounded-loads.html

Index

• Constants
• Variables
• type Consistent
  • func New() *Consistent
  • func NewWithReplicationFactor(replicationFactor int) *Consistent
  • func (c *Consistent) Add(server string)
  • func (c *Consistent) Done(server string)
  • func (c *Consistent) Get(client string) (string, error)
  • func (c *Consistent) GetLeast(client string) (string, error)
  • func (c *Consistent) GetLoads() map[string]int64
  • func (c *Consistent) Inc(server string)
  • func (c *Consistent) MaxLoad() int64
  • func (c *Consistent) Remove(server string) bool
  • func (c *Consistent) Servers() (servers []string)
  • func (c *Consistent) UpdateLoad(server string, load int64)
• type Host

Constants

const OptimalExtraCapacityFactor = 1.25

OptimalExtraCapacityFactor extra factor capacity (1 + ε). The ideal balance between keeping the shards uniform while also keeping consistency when changing shard numbers.

Variables

var ErrNoHosts = errors.New("no hosts added")

Types

type Consistent

type Consistent struct {
	sync.RWMutex
	// contains filtered or unexported fields
}

func New

func New() *Consistent

func NewWithReplicationFactor

func NewWithReplicationFactor(replicationFactor int) *Consistent

func (*Consistent) Add

func (c *Consistent) Add(server string)

func (*Consistent) Done

func (c *Consistent) Done(server string)

Decrements the load of host by 1

should only be used with if you obtained a host with GetLeast

func (*Consistent) Get

func (c *Consistent) Get(client string) (string, error)

Get returns the server that owns the given client. As described in https://en.wikipedia.org/wiki/Consistent_hashing It returns ErrNoHosts if the ring has no servers in it.

func (*Consistent) GetLeast

func (c *Consistent) GetLeast(client string) (string, error)

GetLeast returns the least loaded host that can serve the key. It uses Consistent Hashing With Bounded loads. https://research.googleblog.com/2017/04/consistent-hashing-with-bounded-loads.html It returns ErrNoHosts if the ring has no hosts in it.

func (*Consistent) GetLoads

func (c *Consistent) GetLoads() map[string]int64

Returns the loads of all the hosts

func (*Consistent) Inc

func (c *Consistent) Inc(server string)

Increments the load of host by 1

should only be used with if you obtained a host with GetLeast

func (*Consistent) MaxLoad

func (c *Consistent) MaxLoad() int64

Returns the maximum load of the single host which is: (total_load/number_of_hosts)*1.25 total_load = is the total number of active requests served by hosts for more info: https://research.googleblog.com/2017/04/consistent-hashing-with-bounded-loads.html

func (*Consistent) Remove

func (c *Consistent) Remove(server string) bool

Deletes host from the ring

func (*Consistent) Servers

func (c *Consistent) Servers() (servers []string)

Return the list of servers in the ring

func (*Consistent) UpdateLoad

func (c *Consistent) UpdateLoad(server string, load int64)

Sets the load of `server` to the given `load`

type Host

type Host struct {
	Name string
	Load int64
}