序
本文次要钻研一下dubbo-go的randomLoadBalance
randomLoadBalance
dubbo-go-v1.4.2/cluster/loadbalance/random.go
const ( name = "random")func init() { extension.SetLoadbalance(name, NewRandomLoadBalance)}type randomLoadBalance struct {}// NewRandomLoadBalance ...func NewRandomLoadBalance() cluster.LoadBalance { return &randomLoadBalance{}}- randomLoadBalance的NewRandomLoadBalance办法创立randomLoadBalance
Select
dubbo-go-v1.4.2/cluster/loadbalance/random.go
func (lb *randomLoadBalance) Select(invokers []protocol.Invoker, invocation protocol.Invocation) protocol.Invoker { var length int if length = len(invokers); length == 1 { return invokers[0] } sameWeight := true weights := make([]int64, length) firstWeight := GetWeight(invokers[0], invocation) totalWeight := firstWeight weights[0] = firstWeight for i := 1; i < length; i++ { weight := GetWeight(invokers[i], invocation) weights[i] = weight totalWeight += weight if sameWeight && weight != firstWeight { sameWeight = false } } if totalWeight > 0 && !sameWeight { // If (not every invoker has the same weight & at least one invoker's weight>0), select randomly based on totalWeight. offset := rand.Int63n(totalWeight) for i := 0; i < length; i++ { offset -= weights[i] if offset < 0 { return invokers[i] } } } // If all invokers have the same weight value or totalWeight=0, return evenly. return invokers[rand.Intn(length)]}- Select办法先判断invokers数量，若只有一个则返回invokers[0]；之后遍历invokers计算totalWeight及sameWeight，若totalWeight大于0且sameWeight为false则应用rand.Int63n(totalWeight)随机一个offset，之后遍历weights，用offset挨个去减weights[i]，若offset小于0，则返回invokers[i]；若都没有选中，则返回invokers[rand.Intn(length)]
小结
randomLoadBalance的NewRandomLoadBalance办法创立randomLoadBalance；其Select办法应用了带weight的办法，具体就是应用rand.Int63n(totalWeight)随机一个offset，之后遍历weights，用offset挨个去减weights[i]，若offset小于0，则返回invokers[i]
doc
- random