hash

Documentation

Overview

Package hash provides a consistent hashing function with bounded loads. For more information about the underlying algorithm, please take a look at https://research.googleblog.com/2017/04/consistent-hashing-with-bounded-loads.html

We optimized and simplify this hash algorithm [implementation](https://github.com/buraksezer/consistent/issues/13)

Index

• Variables
• type Config
  • func (c *Config) Sanitize() error
• type ConsistentUniformHash
  • func BuildConsistentUniformHash(numPartitions int, members []Member, config Config) (*ConsistentUniformHash, error)
  • func (c *ConsistentUniformHash) GetPartitionOwner(partID int) Member
  • func (c *ConsistentUniformHash) LoadDistribution() map[string]uint
  • func (c *ConsistentUniformHash) MaxLoad() uint
  • func (c *ConsistentUniformHash) MinLoad() uint
• type Hasher
• type Member
• type PartitionAffinity

Variables

var (
	// ErrInsufficientMemberCount represents an error which means there are not enough members to complete the task.
	ErrInsufficientMemberCount = errors.New("insufficient member count")

	// ErrMemberNotFound represents an error which means requested member could not be found in consistent hash ring.
	ErrMemberNotFound = errors.New("member could not be found in ring")

	// ErrHasherNotProvided will be thrown if the hasher is not provided.
	ErrHasherNotProvided = errors.New("hasher is required")

	// ErrInvalidReplication will be thrown if the replication factor is zero or negative.
	ErrInvalidReplicationFactor = errors.New("positive replication factor is required")

	// ErrInvalidNumPartitions will be thrown if the number of partitions is negative.
	ErrInvalidNumPartitions = errors.New("invalid number of the partitions")

	// ErrEmptyMembers will be thrown if no member is provided.
	ErrEmptyMembers = errors.New("at least one member is required")
)

TODO: Modify these error definitions to coderr.

Types

type Config

type Config struct {
	// Hasher is responsible for generating unsigned, 64 bit hash of provided byte slice.
	Hasher Hasher

	// Keys are distributed among partitions. Prime numbers are good to
	// distribute keys uniformly. Select a big PartitionCount if you have
	// too many keys.
	ReplicationFactor int

	// The rule describes the partition affinity.
	PartitionAffinities []PartitionAffinity
}

Config represents a structure to control consistent package.

func (*Config) Sanitize

func (c *Config) Sanitize() error

type ConsistentUniformHash

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

ConsistentUniformHash generates a uniform distribution of partitions over the members, and this distribution will keep as consistent as possible while the members has some tiny changes.

func BuildConsistentUniformHash

func BuildConsistentUniformHash(numPartitions int, members []Member, config Config) (*ConsistentUniformHash, error)

BuildConsistentUniformHash creates and returns a new hash which is ensured to be uniform and as consistent as possible.

func (*ConsistentUniformHash) GetPartitionOwner

func (c *ConsistentUniformHash) GetPartitionOwner(partID int) Member

GetPartitionOwner returns the owner of the given partition.

func (*ConsistentUniformHash) LoadDistribution

func (c *ConsistentUniformHash) LoadDistribution() map[string]uint

LoadDistribution exposes load distribution of members.

func (*ConsistentUniformHash) MaxLoad

func (c *ConsistentUniformHash) MaxLoad() uint

func (*ConsistentUniformHash) MinLoad

func (c *ConsistentUniformHash) MinLoad() uint

type Hasher

type Hasher interface {
	Sum64([]byte) uint64
}

type Member

type Member interface {
	String() string
}

Member interface represents a member in consistent hash ring.

type PartitionAffinity

type PartitionAffinity struct {
	PartitionID               int
	NumAllowedOtherPartitions uint
}