Documentation
¶
Overview ¶
Package placement is 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
https://github.com/lafikl/consistent/blob/master/consistent.go
Index ¶
- Variables
- type Consistent
- func (c *Consistent) Add(host, id string, port int64) bool
- func (c *Consistent) Done(host string)
- func (c *Consistent) Get(key string) (string, error)
- func (c *Consistent) GetHost(key string) (*Host, error)
- func (c *Consistent) GetLeast(key string) (string, error)
- func (c *Consistent) GetLoads() map[string]int64
- func (c *Consistent) Hosts() (hosts []string)
- func (c *Consistent) Inc(host string)
- func (c *Consistent) MaxLoad() int64
- func (c *Consistent) ReadInternals(reader func(map[uint64]string, []uint64, map[string]*Host, int64))
- func (c *Consistent) Remove(host string) bool
- func (c *Consistent) SortedSet() (sortedSet []uint64)
- func (c *Consistent) UpdateLoad(host string, load int64)
- func (c *Consistent) VirtualNodes() map[uint64]string
- type ConsistentHashTables
- type Host
- type VirtualNodesCache
Constants ¶
This section is empty.
Variables ¶
var ErrNoHosts = errors.New("no hosts added")
ErrNoHosts is an error for no hosts.
Functions ¶
This section is empty.
Types ¶
type Consistent ¶
Consistent represents a data structure for consistent hashing.
func NewConsistentHash ¶
func NewConsistentHash(replicationFactory int64) *Consistent
NewConsistentHash returns a new consistent hash.
func NewFromExisting ¶
func NewFromExisting(loadMap map[string]*Host, replicationFactor int64, virtualNodesCache *VirtualNodesCache) *Consistent
NewFromExisting creates a new consistent hash from existing values.
func (*Consistent) Add ¶
func (c *Consistent) Add(host, id string, port int64) bool
Add adds a host with port to the table. Used on the Placement side to add hosts to the ring. It doesn't calculate vnodes.
func (*Consistent) Done ¶
func (c *Consistent) Done(host string)
Done 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(key string) (string, error)
Get returns the host that owns `key`. It assumes that the struct was created on the Daprd side with NewFromExisting, which is where the hashes are calculated
As described in https://en.wikipedia.org/wiki/Consistent_hashing
It returns ErrNoHosts if the ring has no hosts in it or the hashes haven't been calculated (which how this struct is used on the Placement side)
func (*Consistent) GetHost ¶
func (c *Consistent) GetHost(key string) (*Host, error)
GetHost gets a host.
func (*Consistent) GetLeast ¶
func (c *Consistent) GetLeast(key string) (string, error)
GetLeast uses Consistent Hashing With Bounded loads
https://research.googleblog.com/2017/04/consistent-hashing-with-bounded-loads.html
to pick the least loaded host that can serve the key
It returns ErrNoHosts if the ring has no hosts in it.
func (*Consistent) GetLoads ¶
func (c *Consistent) GetLoads() map[string]int64
GetLoads returns the loads of all the hosts.
func (*Consistent) Hosts ¶
func (c *Consistent) Hosts() (hosts []string)
Hosts return the list of hosts in the ring.
func (*Consistent) Inc ¶
func (c *Consistent) Inc(host string)
Inc 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
MaxLoad 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) ReadInternals ¶ added in v1.7.0
func (c *Consistent) ReadInternals(reader func(map[uint64]string, []uint64, map[string]*Host, int64))
ReadInternals returns the internal data structure of the consistent hash.
func (*Consistent) Remove ¶
func (c *Consistent) Remove(host string) bool
Remove deletes host from the ring.
func (*Consistent) SortedSet ¶ added in v1.13.0
func (c *Consistent) SortedSet() (sortedSet []uint64)
func (*Consistent) UpdateLoad ¶
func (c *Consistent) UpdateLoad(host string, load int64)
UpdateLoad sets the load of `host` to the given `load`.
func (*Consistent) VirtualNodes ¶ added in v1.13.0
func (c *Consistent) VirtualNodes() map[uint64]string
type ConsistentHashTables ¶
type ConsistentHashTables struct {
Version string
Entries map[string]*Consistent
}
ConsistentHashTables is a table holding a map of consistent hashes with a given version.
type VirtualNodesCache ¶ added in v1.13.0
VirtualNodesCache data example:
100 -> (the replication factor) "192.168.1.89:62362" -> ["10056481384176189962", "10100244799470048543"...] (100 elements) "192.168.1.89:62362" -> ["10056481384176189962", "10100244799470048543"...] 200 -> "192.168.1.89:62362" -> ["10056481384176189962", "10100244799470048543"...] (200 elements) "192.168.1.89:62362" -> ["10056481384176189962", "10100244799470048543"...]
func NewVirtualNodesCache ¶ added in v1.13.0
func NewVirtualNodesCache() *VirtualNodesCache
Source Files