micro/selector/selector.go

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// Package selector is a way to load balance service nodes
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package selector
import (
"errors"
"github.com/micro/go-micro/registry"
)
// 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.
type Selector interface {
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Init(opts ...Option) error
Options() Options
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// 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
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// Name of the selector
String() string
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}
// Next is a function that returns the next node
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// based on the selector's strategy
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type Next func() (*registry.Node, error)
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// Filter is used to filter a service during the selection process
type Filter func([]*registry.Service) []*registry.Service
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// Strategy is a selection strategy e.g random, round robin
type Strategy func([]*registry.Service) Next
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var (
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DefaultSelector = newDefaultSelector()
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ErrNotFound = errors.New("not found")
ErrNoneAvailable = errors.New("none available")
)
func NewSelector(opts ...Option) Selector {
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return newDefaultSelector(opts...)
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}