tworandomchoices

Documentation

Overview

Package tworandomchoices provides a load balancer implementation that picks two peers at random and chooses the one with fewer pending requests.

The Power of Two Choices in Randomized Load Balancing: https://www.eecs.harvard.edu/~michaelm/postscripts/tpds2001.pdf

The Power of Two Random Choices: A Survey of Techniques and Results: https://www.eecs.harvard.edu/~michaelm/postscripts/handbook2001.pdf

Index

• func Spec() yarpcconfig.PeerListSpec
• type Configuration
• type List
  • func New(transport peer.Transport, opts ...ListOption) *List
• type ListOption
  • func Capacity(capacity int) ListOption
  • func FailFast() ListOption
  • func Seed(seed int64) ListOption
  • func Source(source rand.Source) ListOption

Functions

func Spec

func Spec() yarpcconfig.PeerListSpec

Spec returns a configuration specification for the "fewest pending requests of two random peers" implementation, making it possible to select the better of two random peer with transports that use outbound peer list configuration (like HTTP).

cfg := yarpcconfig.New()
cfg.MustRegisterPeerList(tworandomchoices.Spec())

This enables the random peer list:

outbounds:
  otherservice:
    unary:
      http:
        url: https://host:port/rpc
        two-random-choices:
          peers:
            - 127.0.0.1:8080
            - 127.0.0.1:8081

Types

type Configuration

type Configuration struct {
	Capacity *int `config:"capacity"`
	FailFast bool `config:"failFast"`
}

Configuration describes how to construct a two-random-choices peer list.

type List

type List struct {
	*peerlist.List
}

List is a PeerList that rotates which peers are to be selected randomly

func New

func New(transport peer.Transport, opts ...ListOption) *List

New creates a new fewest pending requests of two random peers peer list.

type ListOption

type ListOption interface {
	// contains filtered or unexported methods
}

ListOption customizes the behavior of a fewest pending of two random peers list.

func Capacity

func Capacity(capacity int) ListOption

Capacity specifies the default capacity of the underlying data structures for this list.

Defaults to 10.

func FailFast

func FailFast() ListOption

FailFast indicates that the peer list should not wait for a peer to become available when choosing a peer.

This option is preferrable when the better failure mode is to retry from the origin, since another proxy instance might already have a connection.

func Seed

func Seed(seed int64) ListOption

Seed specifies the seed for generating random choices.

func Source

func Source(source rand.Source) ListOption

Source is a source of randomness for the peer list.