Documentation
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Overview ¶
Package consistent provides a consistent hashing function.
Consistent hashing is often used to distribute requests to a changing set of servers. For example, say you have some cache servers cacheA, cacheB, and cacheC. You want to decide which cache server to use to look up information on a user.
You could use a typical hash table and hash the user id to one of cacheA, cacheB, or cacheC. But with a typical hash table, if you add or remove a server, almost all keys will get remapped to different results, which basically could bring your service to a grinding halt while the caches get rebuilt.
With a consistent hash, adding or removing a server drastically reduces the number of keys that get remapped.
Read more about consistent hashing on wikipedia: http://en.wikipedia.org/wiki/Consistent_hashing
Index ¶
- Variables
- type Consistent
- func (c *Consistent) Add(node proto.Node) (err error)
- func (c *Consistent) AddCache(node proto.Node)
- func (c *Consistent) GetNeighbor(name string) (proto.Node, error)
- func (c *Consistent) GetNeighbors(name string, n int) ([]proto.Node, error)
- func (c *Consistent) GetNeighborsEx(name string, n int, roles proto.ServerRoles) ([]proto.Node, error)
- func (c *Consistent) GetNode(name string) (*proto.Node, error)
- func (c *Consistent) GetTwoNeighbors(name string) (proto.Node, proto.Node, error)
- func (c *Consistent) Remove(nodeID proto.NodeID) (err error)
- func (c *Consistent) RemoveCache(nodeID proto.NodeID)
- func (c *Consistent) ResetCache()
- func (c *Consistent) Set(nodes []proto.Node) (err error)
- type KMSStorage
- func (s *KMSStorage) DelNode(nodeID proto.NodeID) (err error)
- func (s *KMSStorage) GetAllNodeInfo() (nodes []proto.Node, err error)
- func (s *KMSStorage) Init(storePath string, initNodes []proto.Node) (err error)
- func (s *KMSStorage) Reset() (err error)
- func (s *KMSStorage) SetNode(node *proto.Node) (err error)
- type NodeKeys
- type Persistence
Constants ¶
This section is empty.
Variables ¶
var ( // ErrEmptyCircle is the error returned when trying to get an node when nothing has been added to hash. ErrEmptyCircle = errors.New("empty circle") // ErrKeyNotFound is the error returned when no key in circle ErrKeyNotFound = errors.New("node key not found") )
Functions ¶
This section is empty.
Types ¶
type Consistent ¶
type Consistent struct {
NumberOfReplicas int
sync.RWMutex
// contains filtered or unexported fields
}
Consistent holds the information about the members of the consistent hash circle.
func InitConsistent ¶
func InitConsistent(storePath string, persistImpl Persistence, initBP bool) (c *Consistent, err error)
InitConsistent creates a new Consistent object with a default setting of 20 replicas for each entry.
func (*Consistent) Add ¶
func (c *Consistent) Add(node proto.Node) (err error)
Add inserts a string node in the consistent hash.
func (*Consistent) AddCache ¶
func (c *Consistent) AddCache(node proto.Node)
AddCache only adds c.circle skips persist.
func (*Consistent) GetNeighbor ¶
func (c *Consistent) GetNeighbor(name string) (proto.Node, error)
GetNeighbor returns an node close to where name hashes to in the circle.
func (*Consistent) GetNeighbors ¶
GetNeighbors returns the N closest distinct nodes to the name input in the circle.
func (*Consistent) GetNeighborsEx ¶
func (c *Consistent) GetNeighborsEx(name string, n int, roles proto.ServerRoles) ([]proto.Node, error)
GetNeighborsEx returns the N closest distinct nodes to the name input in the circle.
func (*Consistent) GetNode ¶
func (c *Consistent) GetNode(name string) (*proto.Node, error)
GetNode returns an node by its node id.
func (*Consistent) GetTwoNeighbors ¶
GetTwoNeighbors returns the two closest distinct nodes to the name input in the circle.
func (*Consistent) Remove ¶
func (c *Consistent) Remove(nodeID proto.NodeID) (err error)
Remove removes an node from the hash.
func (*Consistent) RemoveCache ¶
func (c *Consistent) RemoveCache(nodeID proto.NodeID)
RemoveCache removes an node from the hash cache.
func (*Consistent) ResetCache ¶
func (c *Consistent) ResetCache()
ResetCache removes all node from the hash cache.
type KMSStorage ¶
type KMSStorage struct{}
KMSStorage implements Persistence.
func (*KMSStorage) DelNode ¶
func (s *KMSStorage) DelNode(nodeID proto.NodeID) (err error)
DelNode implements Persistence interface.
func (*KMSStorage) GetAllNodeInfo ¶
func (s *KMSStorage) GetAllNodeInfo() (nodes []proto.Node, err error)
GetAllNodeInfo implements Persistence interface.
func (*KMSStorage) Init ¶
func (s *KMSStorage) Init(storePath string, initNodes []proto.Node) (err error)
Init implements Persistence interface.
func (*KMSStorage) Reset ¶
func (s *KMSStorage) Reset() (err error)
Reset implements Persistence interface.
type NodeKeys ¶
NodeKeys is NodeKey array.
type Persistence ¶
type Persistence interface {
Init(storePath string, initNode []proto.Node) (err error)
SetNode(node *proto.Node) (err error)
DelNode(nodeID proto.NodeID) (err error)
Reset() error
GetAllNodeInfo() (nodes []proto.Node, err error)
}
Persistence is the interface for consistent persistence.
Source Files