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package policy
import (
"math/rand"
"sync/atomic"
)
// Policy defines a policy we use for selecting upstreams.
type Policy interface {
List(policy ...interface{}) []interface{}
String() string
}
// Random is a policy that implements random upstream selection.
type Random struct{}
var _ Policy = &Random{}
// String returns the name of policy Random
func (r *Random) String() string { return "random" }
// List returns a set of proxies to be used for this client depending on Random policy.
func (r *Random) List(p ...interface{}) []interface{} {
switch len(p) {
case 1:
return p
case 2:
if rand.Int()%2 == 0 {
return []interface{}{p[1], p[0]} // swap
}
return p
}
perms := rand.Perm(len(p))
rnd := make([]interface{}, len(p))
for i, p1 := range perms {
rnd[i] = p[p1]
}
return rnd
}
// RoundRobin is a policy that selects hosts based on round robin ordering.
type RoundRobin struct {
robin uint32
}
var _ Policy = &RoundRobin{}
// String returns the name of policy RoundRobin
func (r *RoundRobin) String() string { return "round_robin" }
// List returns a set of proxies to be used for this client depending on RoundRobin policy.
func (r *RoundRobin) List(p ...interface{}) []interface{} {
poolLen := uint32(len(p))
i := atomic.AddUint32(&r.robin, 1) % poolLen
robin := []interface{}{p[i]}
robin = append(robin, p[:i]...)
robin = append(robin, p[i+1:]...)
return robin
}
// Sequential is a policy that selects hosts based on sequential ordering.
type Sequential struct{}
var _ Policy = &Sequential{}
// String returns the name of policy Sequential
func (r *Sequential) String() string { return "sequential" }
// List returns a set of proxies without filter.
func (r *Sequential) List(p ...interface{}) []interface{} {
return p
}
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