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
Index ¶
- Variables
- type Consistent
- func (c *Consistent) Add(host 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) GetInternals() (map[uint64]string, []uint64, map[string]*Host, int64)
- 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) Remove(host string) bool
- func (c *Consistent) UpdateLoad(host string, load int64)
- type Host
- type PlacementService
- func (p *PlacementService) PerformTablesUpdate(hosts []daprinternal_pb.PlacementService_ReportDaprStatusServer, ...)
- func (p *PlacementService) ProcessHost(host *daprinternal_pb.Host)
- func (p *PlacementService) ProcessRemovedHost(id string)
- func (p *PlacementService) RemoveHost(srv daprinternal_pb.PlacementService_ReportDaprStatusServer)
- func (p *PlacementService) ReportDaprStatus(srv daprinternal_pb.PlacementService_ReportDaprStatusServer) error
- func (p *PlacementService) Run(port string)
- type PlacementTables
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() *Consistent
NewConsistentHash returns a new consistent hash
func NewFromExisting ¶
func NewFromExisting(hosts map[uint64]string, sortedSet []uint64, loadMap map[string]*Host) *Consistent
NewFromExisting creates a new consistent hash from existing values
func (*Consistent) Add ¶
func (c *Consistent) Add(host string, port int64) bool
Add adds a host with port to the table
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`.
As described in https://en.wikipedia.org/wiki/Consistent_hashing
It returns ErrNoHosts if the ring has no hosts in it.
func (*Consistent) GetHost ¶
func (c *Consistent) GetHost(key string) (*Host, error)
GetHost gets a host
func (*Consistent) GetInternals ¶
GetInternals returns the internal data structure of the consistent hash
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) Remove ¶
func (c *Consistent) Remove(host string) bool
Remove deletes host from the ring
func (*Consistent) UpdateLoad ¶
func (c *Consistent) UpdateLoad(host string, load int64)
UpdateLoad sets the load of `host` to the given `load`
type PlacementService ¶
type PlacementService struct {
// contains filtered or unexported fields
}
PlacementService updates the Dapr runtimes with distributed hash tables for stateful entities.
func NewPlacementService ¶
func NewPlacementService() *PlacementService
NewPlacementService returns a new placement service
func (*PlacementService) PerformTablesUpdate ¶
func (p *PlacementService) PerformTablesUpdate(hosts []daprinternal_pb.PlacementService_ReportDaprStatusServer, options placementOptions)
PerformTablesUpdate updates the connected dapr runtimes using a 3 stage commit. first it locks so no further dapr can be taken it then proceeds to update and then unlock once all runtimes have been updated
func (*PlacementService) ProcessHost ¶
func (p *PlacementService) ProcessHost(host *daprinternal_pb.Host)
ProcessHost updates the distributed has list based on a new host and its entities
func (*PlacementService) ProcessRemovedHost ¶
func (p *PlacementService) ProcessRemovedHost(id string)
ProcessRemovedHost removes a host from the hash table
func (*PlacementService) RemoveHost ¶
func (p *PlacementService) RemoveHost(srv daprinternal_pb.PlacementService_ReportDaprStatusServer)
RemoveHost removes the host from the hosts list
func (*PlacementService) ReportDaprStatus ¶
func (p *PlacementService) ReportDaprStatus(srv daprinternal_pb.PlacementService_ReportDaprStatusServer) error
ReportDaprStatus gets a heartbeat report from different Dapr hosts
func (*PlacementService) Run ¶
func (p *PlacementService) Run(port string)
Run starts the placement service gRPC server
type PlacementTables ¶
type PlacementTables struct {
Version string
Entries map[string]*Consistent
}
PlacementTables is a table holding a map of consistent hashes with a given version
func NewPlacementTables ¶
func NewPlacementTables(version string, entries map[string]*Consistent) *PlacementTables
NewPlacementTables returns new stateful placement tables with a given version
Source Files