| /* |
| * |
| * Copyright 2019 gRPC authors. |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package wrr |
| |
| import "google.golang.org/grpc/internal/grpcrand" |
| |
| // weightedItem is a wrapped weighted item that is used to implement weighted random algorithm. |
| type weightedItem struct { |
| Item interface{} |
| Weight int64 |
| } |
| |
| // randomWRR is a struct that contains weighted items implement weighted random algorithm. |
| type randomWRR struct { |
| items []*weightedItem |
| sumOfWeights int64 |
| } |
| |
| // NewRandom creates a new WRR with random. |
| func NewRandom() WRR { |
| return &randomWRR{} |
| } |
| |
| var grpcrandInt63n = grpcrand.Int63n |
| |
| func (rw *randomWRR) Next() (item interface{}) { |
| if rw.sumOfWeights == 0 { |
| return nil |
| } |
| // Random number in [0, sum). |
| randomWeight := grpcrandInt63n(rw.sumOfWeights) |
| for _, item := range rw.items { |
| randomWeight = randomWeight - item.Weight |
| if randomWeight < 0 { |
| return item.Item |
| } |
| } |
| |
| return rw.items[len(rw.items)-1].Item |
| } |
| |
| func (rw *randomWRR) Add(item interface{}, weight int64) { |
| rItem := &weightedItem{Item: item, Weight: weight} |
| rw.items = append(rw.items, rItem) |
| rw.sumOfWeights += weight |
| } |