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selector.go
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selector.go
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// Copyright © by Jeff Foley 2022-2024. All rights reserved.
// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
// SPDX-License-Identifier: Apache-2.0
package resolve
import (
"math/rand"
"sync"
)
type selector interface {
// GetResolver returns a resolver managed by the selector.
GetResolver() *resolver
// LookupResolver returns the resolver with the matching address.
LookupResolver(addr string) *resolver
// AddResolver adds a resolver to the selector pool.
AddResolver(res *resolver)
// AllResolvers returns all the resolver objects currently managed by the selector.
AllResolvers() []*resolver
// Len returns the number of resolver objects currently managed by the selector.
Len() int
// Close releases all resources allocated by the selector.
Close()
}
type randomSelector struct {
sync.Mutex
list []*resolver
lookup map[string]*resolver
}
func newRandomSelector() *randomSelector {
return &randomSelector{lookup: make(map[string]*resolver)}
}
// GetResolver performs random selection on the pool of resolvers.
func (r *randomSelector) GetResolver() *resolver {
max := r.maxQPS()
if max == -1 {
return nil
}
sel := rand.Intn(max)
r.Lock()
defer r.Unlock()
var cur int
var chosen *resolver
loop:
for _, res := range r.list {
select {
case <-res.done:
continue loop
default:
}
cur += res.qps
if sel < cur {
chosen = res
break
}
}
return chosen
}
func (r *randomSelector) maxQPS() int {
r.Lock()
defer r.Unlock()
if len(r.list) == 0 {
return -1
}
var max int
for _, res := range r.list {
select {
case <-res.done:
default:
max += res.qps
}
}
return max
}
func (r *randomSelector) LookupResolver(addr string) *resolver {
r.Lock()
defer r.Unlock()
return r.lookup[addr]
}
func (r *randomSelector) AddResolver(res *resolver) {
r.Lock()
defer r.Unlock()
if _, found := r.lookup[res.address.IP.String()]; !found {
r.list = append(r.list, res)
r.lookup[res.address.IP.String()] = res
}
}
func (r *randomSelector) AllResolvers() []*resolver {
r.Lock()
defer r.Unlock()
var active []*resolver
for _, res := range r.list {
select {
case <-res.done:
default:
active = append(active, res)
}
}
return active
}
func (r *randomSelector) Len() int {
r.Lock()
defer r.Unlock()
var count int
for _, res := range r.list {
select {
case <-res.done:
default:
count++
}
}
return count
}
func (r *randomSelector) Close() {
r.Lock()
defer r.Unlock()
r.list = nil
r.lookup = nil
}
func min(x, y int) int {
m := x
if y < m {
m = y
}
return m
}