aa7818e1d3
* Update to avoid pseudo-random number This PR update the usage of rand so that non-global seed is used. Signed-off-by: Yong Tang <yong.tang.github@outlook.com> * Add concurrency-safe random source See https://stackoverflow.com/questions/48958886/how-to-create-a-thread-safe-rand-source Signed-off-by: Yong Tang <yong.tang.github@outlook.com>
68 lines
1.3 KiB
Go
68 lines
1.3 KiB
Go
package grpc
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import (
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"sync/atomic"
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"time"
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"github.com/coredns/coredns/plugin/pkg/rand"
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)
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// Policy defines a policy we use for selecting upstreams.
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type Policy interface {
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List([]*Proxy) []*Proxy
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String() string
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}
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// random is a policy that implements random upstream selection.
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type random struct{}
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func (r *random) String() string { return "random" }
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func (r *random) List(p []*Proxy) []*Proxy {
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switch len(p) {
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case 1:
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return p
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case 2:
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if rn.Int()%2 == 0 {
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return []*Proxy{p[1], p[0]} // swap
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}
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return p
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}
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perms := rn.Perm(len(p))
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rnd := make([]*Proxy, len(p))
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for i, p1 := range perms {
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rnd[i] = p[p1]
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}
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return rnd
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}
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// roundRobin is a policy that selects hosts based on round robin ordering.
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type roundRobin struct {
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robin uint32
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}
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func (r *roundRobin) String() string { return "round_robin" }
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func (r *roundRobin) List(p []*Proxy) []*Proxy {
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poolLen := uint32(len(p))
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i := atomic.AddUint32(&r.robin, 1) % poolLen
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robin := []*Proxy{p[i]}
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robin = append(robin, p[:i]...)
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robin = append(robin, p[i+1:]...)
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return robin
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}
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// sequential is a policy that selects hosts based on sequential ordering.
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type sequential struct{}
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func (r *sequential) String() string { return "sequential" }
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func (r *sequential) List(p []*Proxy) []*Proxy {
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return p
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}
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var rn = rand.New(time.Now().UnixNano())
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