selector

Documentation

Overview

The Selector package provides a way to algorithmically filter and return nodes required by the client or any other system. Selector's implemented by Micro build on the registry but it's of optional use. One could provide a static Selector that has a fixed pool.

Index

• Variables
• type Filter
  • func FilterEndpoint(name string) Filter
  • func FilterLabel(key, val string) Filter
  • func FilterVersion(version string) Filter
• type Next
  • func Random(services []*registry.Service) Next
  • func RoundRobin(services []*registry.Service) Next
• type Option
  • func Registry(r registry.Registry) Option
  • func SetStrategy(fn Strategy) Option
• type Options
• type SelectOption
  • func WithFilter(fn ...Filter) SelectOption
  • func WithStrategy(fn Strategy) SelectOption
• type SelectOptions
• type Selector
  • func NewSelector(opts ...Option) Selector
• type Strategy

Variables

var (
	DefaultSelector = newDefaultSelector()

	ErrNotFound      = errors.New("not found")
	ErrNoneAvailable = errors.New("none available")
)

Types

type Filter

type Filter func([]*registry.Service) []*registry.Service

Filter is used to filter a service during the selection process

func FilterEndpoint

func FilterEndpoint(name string) Filter

FilterEndpoint is an endpoint based Select Filter which will only return services with the endpoint specified.

func FilterLabel

func FilterLabel(key, val string) Filter

FilterLabel is a label based Select Filter which will only return services with the label specified.

func FilterVersion

func FilterVersion(version string) Filter

FilterVersion is a version based Select Filter which will only return services with the version specified.

type Next

type Next func() (*registry.Node, error)

Next is a function that returns the next node based on the selector's strategy

func Random

func Random(services []*registry.Service) Next

Random is a random strategy algorithm for node selection

func RoundRobin

func RoundRobin(services []*registry.Service) Next

RoundRobin is a roundrobin strategy algorithm for node selection

type Option

type Option func(*Options)

Option used to initialise the selector

func Registry

func Registry(r registry.Registry) Option

Registry sets the registry used by the selector

func SetStrategy

func SetStrategy(fn Strategy) Option

SetStrategy sets the default strategy for the selector

type Options

type Options struct {
	Registry registry.Registry
	Strategy Strategy

	// Other options for implementations of the interface
	// can be stored in a context
	Context context.Context
}

type SelectOption

type SelectOption func(*SelectOptions)

SelectOption used when making a select call

func WithFilter

func WithFilter(fn ...Filter) SelectOption

WithFilter adds a filter function to the list of filters used during the Select call.

func WithStrategy

func WithStrategy(fn Strategy) SelectOption

Strategy sets the selector strategy

type SelectOptions

type SelectOptions struct {
	Filters  []Filter
	Strategy Strategy

	// Other options for implementations of the interface
	// can be stored in a context
	Context context.Context
}

type Selector

type Selector interface {
	Init(opts ...Option) error
	Options() Options
	// Select returns a function which should return the next node
	Select(service string, opts ...SelectOption) (Next, error)
	// Mark sets the success/error against a node
	Mark(service string, node *registry.Node, err error)
	// Reset returns state back to zero for a service
	Reset(service string)
	// Close renders the selector unusable
	Close() error
	// Name of the selector
	String() string
}

Selector builds on the registry as a mechanism to pick nodes and mark their status. This allows host pools and other things to be built using various algorithms.

func NewSelector

func NewSelector(opts ...Option) Selector

type Strategy

type Strategy func([]*registry.Service) Next

Strategy is a selection strategy e.g random, round robin