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(osd *pb.Osd)
- func (c *Consistent) Get(name string) (*pb.Osd, error)
- func (c *Consistent) GetN(name string, n int) ([]*pb.Osd, error)
- func (c *Consistent) GetTwo(name string) (*pb.Osd, *pb.Osd, error)
- func (c *Consistent) Members() []string
- func (c *Consistent) Remove(osd *pb.Osd)
- func (c *Consistent) Set(osdMap *pb.OsdMap)
Constants ¶
This section is empty.
Variables ¶
var ErrEmptyCircle = errors.New("empty circle")
ErrEmptyCircle is the error returned when trying to get an element when nothing has been added to hash.
Functions ¶
This section is empty.
Types ¶
type Consistent ¶
Consistent holds the information about the members of the consistent hash circle.
func New ¶
func New(osdMap *pb.OsdMap, policy pb.DistributePolicy) *Consistent
New creates a new Consistent object with a default setting of 10 replicas for weight 1.
To change the number of replicas, set NumberOfReplicas before adding entries.
func (*Consistent) Add ¶
func (c *Consistent) Add(osd *pb.Osd)
Add inserts a osd in the consistent hash.
func (*Consistent) Get ¶
func (c *Consistent) Get(name string) (*pb.Osd, error)
Get returns an element close to where name hashes to in the circle.
func (*Consistent) GetN ¶
GetN returns the N closest distinct elements to the name input in the circle.
func (*Consistent) GetTwo ¶
GetTwo returns the two closest distinct elements to the name input in the circle.
func (*Consistent) Members ¶
func (c *Consistent) Members() []string
func (*Consistent) Remove ¶
func (c *Consistent) Remove(osd *pb.Osd)
Remove removes an element from the hash.
func (*Consistent) Set ¶
func (c *Consistent) Set(osdMap *pb.OsdMap)
Set sets all the elements in the hash. If there are existing elements not present in elts, they will be removed.
Source Files