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p2c.go
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p2c.go
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package p2c
import (
"context"
"fmt"
"math"
"math/rand"
"strings"
"sync"
"sync/atomic"
"time"
"github.com/yilefreedom/go-zero/core/logx"
"github.com/yilefreedom/go-zero/core/syncx"
"github.com/yilefreedom/go-zero/core/timex"
"github.com/yilefreedom/go-zero/zrpc/internal/codes"
"google.golang.org/grpc/balancer"
"google.golang.org/grpc/balancer/base"
"google.golang.org/grpc/resolver"
)
const (
Name = "p2c_ewma"
decayTime = int64(time.Second * 10) // default value from finagle
forcePick = int64(time.Second)
initSuccess = 1000
throttleSuccess = initSuccess / 2
penalty = int64(math.MaxInt32)
pickTimes = 3
logInterval = time.Minute
)
func init() {
balancer.Register(newBuilder())
}
type p2cPickerBuilder struct {
}
func newBuilder() balancer.Builder {
return base.NewBalancerBuilder(Name, new(p2cPickerBuilder))
}
func (b *p2cPickerBuilder) Build(readySCs map[resolver.Address]balancer.SubConn) balancer.Picker {
if len(readySCs) == 0 {
return base.NewErrPicker(balancer.ErrNoSubConnAvailable)
}
var conns []*subConn
for addr, conn := range readySCs {
conns = append(conns, &subConn{
addr: addr,
conn: conn,
success: initSuccess,
})
}
return &p2cPicker{
conns: conns,
r: rand.New(rand.NewSource(time.Now().UnixNano())),
stamp: syncx.NewAtomicDuration(),
}
}
type p2cPicker struct {
conns []*subConn
r *rand.Rand
stamp *syncx.AtomicDuration
lock sync.Mutex
}
func (p *p2cPicker) Pick(ctx context.Context, info balancer.PickInfo) (
conn balancer.SubConn, done func(balancer.DoneInfo), err error) {
p.lock.Lock()
defer p.lock.Unlock()
var chosen *subConn
switch len(p.conns) {
case 0:
return nil, nil, balancer.ErrNoSubConnAvailable
case 1:
chosen = p.choose(p.conns[0], nil)
case 2:
chosen = p.choose(p.conns[0], p.conns[1])
default:
var node1, node2 *subConn
for i := 0; i < pickTimes; i++ {
a := p.r.Intn(len(p.conns))
b := p.r.Intn(len(p.conns) - 1)
if b >= a {
b++
}
node1 = p.conns[a]
node2 = p.conns[b]
if node1.healthy() && node2.healthy() {
break
}
}
chosen = p.choose(node1, node2)
}
atomic.AddInt64(&chosen.inflight, 1)
atomic.AddInt64(&chosen.requests, 1)
return chosen.conn, p.buildDoneFunc(chosen), nil
}
func (p *p2cPicker) buildDoneFunc(c *subConn) func(info balancer.DoneInfo) {
start := int64(timex.Now())
return func(info balancer.DoneInfo) {
atomic.AddInt64(&c.inflight, -1)
now := timex.Now()
last := atomic.SwapInt64(&c.last, int64(now))
td := int64(now) - last
if td < 0 {
td = 0
}
w := math.Exp(float64(-td) / float64(decayTime))
lag := int64(now) - start
if lag < 0 {
lag = 0
}
olag := atomic.LoadUint64(&c.lag)
if olag == 0 {
w = 0
}
atomic.StoreUint64(&c.lag, uint64(float64(olag)*w+float64(lag)*(1-w)))
success := initSuccess
if info.Err != nil && !codes.Acceptable(info.Err) {
success = 0
}
osucc := atomic.LoadUint64(&c.success)
atomic.StoreUint64(&c.success, uint64(float64(osucc)*w+float64(success)*(1-w)))
stamp := p.stamp.Load()
if now-stamp >= logInterval {
if p.stamp.CompareAndSwap(stamp, now) {
p.logStats()
}
}
}
}
func (p *p2cPicker) choose(c1, c2 *subConn) *subConn {
start := int64(timex.Now())
if c2 == nil {
atomic.StoreInt64(&c1.pick, start)
return c1
}
if c1.load() > c2.load() {
c1, c2 = c2, c1
}
pick := atomic.LoadInt64(&c2.pick)
if start-pick > forcePick && atomic.CompareAndSwapInt64(&c2.pick, pick, start) {
return c2
} else {
atomic.StoreInt64(&c1.pick, start)
return c1
}
}
func (p *p2cPicker) logStats() {
var stats []string
p.lock.Lock()
defer p.lock.Unlock()
for _, conn := range p.conns {
stats = append(stats, fmt.Sprintf("conn: %s, load: %d, reqs: %d",
conn.addr.Addr, conn.load(), atomic.SwapInt64(&conn.requests, 0)))
}
logx.Statf("p2c - %s", strings.Join(stats, "; "))
}
type subConn struct {
addr resolver.Address
conn balancer.SubConn
lag uint64
inflight int64
success uint64
requests int64
last int64
pick int64
}
func (c *subConn) healthy() bool {
return atomic.LoadUint64(&c.success) > throttleSuccess
}
func (c *subConn) load() int64 {
// plus one to avoid multiply zero
lag := int64(math.Sqrt(float64(atomic.LoadUint64(&c.lag) + 1)))
load := lag * (atomic.LoadInt64(&c.inflight) + 1)
if load == 0 {
return penalty
} else {
return load
}
}