github.com/cloudwego/kitex@v0.9.0/pkg/loadbalance/weighted_random.go (about)

     1  /*
     2   * Copyright 2023 CloudWeGo Authors
     3   *
     4   * Licensed under the Apache License, Version 2.0 (the "License");
     5   * you may not use this file except in compliance with the License.
     6   * You may obtain a copy of the License at
     7   *
     8   *     http://www.apache.org/licenses/LICENSE-2.0
     9   *
    10   * Unless required by applicable law or agreed to in writing, software
    11   * distributed under the License is distributed on an "AS IS" BASIS,
    12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13   * See the License for the specific language governing permissions and
    14   * limitations under the License.
    15   */
    16  
    17  package loadbalance
    18  
    19  import (
    20  	"context"
    21  
    22  	"github.com/bytedance/gopkg/lang/fastrand"
    23  
    24  	"github.com/cloudwego/kitex/pkg/discovery"
    25  )
    26  
    27  type weightedRandomPicker struct {
    28  	instances []discovery.Instance
    29  	weightSum int
    30  }
    31  
    32  func newWeightedRandomPickerWithSum(instances []discovery.Instance, weightSum int) Picker {
    33  	return &weightedRandomPicker{
    34  		instances: instances,
    35  		weightSum: weightSum,
    36  	}
    37  }
    38  
    39  // Next implements the Picker interface.
    40  func (wp *weightedRandomPicker) Next(ctx context.Context, request interface{}) (ins discovery.Instance) {
    41  	weight := fastrand.Intn(wp.weightSum)
    42  	for i := 0; i < len(wp.instances); i++ {
    43  		weight -= wp.instances[i].Weight()
    44  		if weight < 0 {
    45  			return wp.instances[i]
    46  		}
    47  	}
    48  	return nil
    49  }
    50  
    51  type randomPicker struct {
    52  	instances []discovery.Instance
    53  }
    54  
    55  func newRandomPicker(instances []discovery.Instance) Picker {
    56  	return &randomPicker{
    57  		instances: instances,
    58  	}
    59  }
    60  
    61  // Next implements the Picker interface.
    62  func (rp *randomPicker) Next(ctx context.Context, request interface{}) (ins discovery.Instance) {
    63  	idx := fastrand.Intn(len(rp.instances))
    64  	return rp.instances[idx]
    65  }