consistenthash

Documentation

Index

• Constants
• func StableHash(data []byte) uint64
• type ConsistentHash
  • func (ch *ConsistentHash) AddBuckets(newBuckets ...string) (ok bool)
  • func (ch *ConsistentHash) Assignment(item string) (bucket string)
  • func (ch *ConsistentHash) Assignments(items ...string) map[string][]string
  • func (ch *ConsistentHash) Buckets() (buckets []string)
  • func (ch *ConsistentHash) HashFunctionOrDefault() HashFunction
  • func (ch *ConsistentHash) IsAssigned(bucket, item string) (ok bool)
  • func (ch *ConsistentHash) MarshalJSON() ([]byte, error)
  • func (ch *ConsistentHash) RemoveBucket(toRemove string) (ok bool)
  • func (ch *ConsistentHash) ReplicasOrDefault() int
  • func (ch *ConsistentHash) String() string
• type HashFunction
• type HashedBucket

Constants

const (
	// DefaultReplicas is the default number of bucket virtual replicas.
	DefaultReplicas = 16
)

Functions

func StableHash

func StableHash(data []byte) uint64

StableHash implements the default hash function with a stable crc64 table checksum.

Types

type ConsistentHash

type ConsistentHash struct {
	Replicas     int
	HashFunction HashFunction
	// contains filtered or unexported fields
}

ConsistentHash creates hashed assignments for each bucket.

func (*ConsistentHash) AddBuckets

func (ch *ConsistentHash) AddBuckets(newBuckets ...string) (ok bool)

AddBuckets adds a list of buckets to the consistent hash, and returns a boolean indiciating if _any_ buckets were added.

If any of the new buckets do not exist on the hash ring the new bucket will be inserted `ReplicasOrDefault` number of times into the internal hashring.

If any of the new buckets already exist on the hash ring no action is taken for that bucket.

Calling `AddBuckets` is safe to do concurrently and acquires a write lock on the consistent hash reference.

func (*ConsistentHash) Assignment

func (ch *ConsistentHash) Assignment(item string) (bucket string)

Assignment returns the bucket assignment for a given item.

Calling `Assignment` is safe to do concurrently and acquires a read lock on the consistent hash reference.

func (*ConsistentHash) Assignments

func (ch *ConsistentHash) Assignments(items ...string) map[string][]string

Assignments returns the assignments for a given list of items organized by the name of the bucket, and an array of the assigned items.

Calling `Assignments` is safe to do concurrently and acquires a read lock on the consistent hash reference.

func (*ConsistentHash) Buckets

func (ch *ConsistentHash) Buckets() (buckets []string)

Buckets returns the buckets.

Calling `Buckets` is safe to do concurrently and acquires a read lock on the consistent hash reference.

func (*ConsistentHash) HashFunctionOrDefault

func (ch *ConsistentHash) HashFunctionOrDefault() HashFunction

HashFunctionOrDefault returns the provided hash function or a default.

func (*ConsistentHash) IsAssigned

func (ch *ConsistentHash) IsAssigned(bucket, item string) (ok bool)

IsAssigned returns if a given bucket is assigned a given item.

Calling `IsAssigned` is safe to do concurrently and acquires a read lock on the consistent hash reference.

func (*ConsistentHash) MarshalJSON

func (ch *ConsistentHash) MarshalJSON() ([]byte, error)

MarshalJSON marshals the consistent hash as json.

The form of the returned json is the underlying []HashedBucket and there is no corresponding `UnmarshalJSON` because it is uncertain on the other end what the hashfunction is because functions can't be json serialized.

You should use MarshalJSON for communicating information for debugging purposes only.

Calling `MarshalJSON` is safe to do concurrently and acquires a read lock on the consistent hash reference.

func (*ConsistentHash) RemoveBucket

func (ch *ConsistentHash) RemoveBucket(toRemove string) (ok bool)

RemoveBucket removes a bucket from the consistent hash, and returns a boolean indicating if the provided bucket was found.

If the bucket exists on the hash ring, the bucket and its replicas are removed.

If the bucket does not exist on the ring, no action is taken.

Calling `RemoveBucket` is safe to do concurrently and acquires a write lock on the consistent hash reference.

func (*ConsistentHash) ReplicasOrDefault

func (ch *ConsistentHash) ReplicasOrDefault() int

ReplicasOrDefault is the default number of bucket virtual replicas.

func (*ConsistentHash) String

func (ch *ConsistentHash) String() string

String returns a string form of the hash for debugging purposes.

Calling `String` is safe to do concurrently and acquires a read lock on the consistent hash reference.

type HashFunction

type HashFunction func([]byte) uint64

HashFunction is a function that can be used to hash items.

type HashedBucket

type HashedBucket struct {
	Hashcode uint64 `json:"hashcode"`
	Bucket   string `json:"bucket"`
	Replica  int    `json:"replica"`
}

HashedBucket is a bucket in the hashring that holds the hashcode, the bucket name (as Bucket) and the virtual replica index.