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added code comments (#4219)

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guonaihong 2024-07-13 20:09:58 +08:00 committed by GitHub
parent ec86f22cd6
commit 775b105ab2
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1 changed files with 16 additions and 7 deletions
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23
zrpc/internal/balancer/p2c/p2c.go
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@ -23,12 +23,12 @@ const (
Name = "p2c_ewma" Name = "p2c_ewma"
decayTime = int64(time.Second * 10) // default value from finagle decayTime = int64(time.Second * 10) // default value from finagle
forcePick = int64(time.Second) forcePick = int64(time.Second) // If a node is not selected for a period of time, it is forcibly selected.
initSuccess = 1000 initSuccess = 1000 // Initial success count
throttleSuccess = initSuccess / 2 throttleSuccess = initSuccess / 2 // Success count to trigger throttling
penalty = int64(math.MaxInt32) penalty = int64(math.MaxInt32) // Penalty value for load calculation
pickTimes = 3 pickTimes = 3 // Number of pick attempts
logInterval = time.Minute logInterval = time.Minute // Log interval for statistics
) )
var emptyPickResult balancer.PickResult var emptyPickResult balancer.PickResult
@ -121,6 +121,10 @@ func (p *p2cPicker) buildDoneFunc(c *subConn) func(info balancer.DoneInfo) {
if td < 0 { if td < 0 {
td = 0 td = 0
} }
// As the td/decayTime value increases, indicating an increase in delay, the value of w (y axis) will decrease, inversely proportional.
// The function curve of y = x^(-x) is as follows.
// https://github.com/zeromicro/zero-doc/blob/main/doc/images/y_e_x.png?raw=true
w := math.Exp(float64(-td) / float64(decayTime)) w := math.Exp(float64(-td) / float64(decayTime))
lag := int64(now) - start lag := int64(now) - start
if lag < 0 { if lag < 0 {
@ -130,6 +134,8 @@ func (p *p2cPicker) buildDoneFunc(c *subConn) func(info balancer.DoneInfo) {
if olag == 0 { if olag == 0 {
w = 0 w = 0
} }
// The smaller the value of w, the lower the impact of historical data.
atomic.StoreUint64(&c.lag, uint64(float64(olag)*w+float64(lag)*(1-w))) atomic.StoreUint64(&c.lag, uint64(float64(olag)*w+float64(lag)*(1-w)))
success := initSuccess success := initSuccess
if info.Err != nil && !codes.Acceptable(info.Err) { if info.Err != nil && !codes.Acceptable(info.Err) {
@ -182,7 +188,10 @@ func (p *p2cPicker) logStats() {
} }
type subConn struct { type subConn struct {
lag uint64 // The request latency measured by the weighted moving average algorithm.
lag uint64
// The value represents the number of requests that are either pending or just starting at the current node, and it is obtained through atomic addition.
inflight int64 inflight int64
success uint64 success uint64
requests int64 requests int64