github.com/hxx258456/ccgo@v0.0.5-0.20230213014102-48b35f46f66f/grpc/internal/testutils/wrr.go (about)

     1  /*
     2   *
     3   * Copyright 2020 gRPC authors.
     4   *
     5   * Licensed under the Apache License, Version 2.0 (the "License");
     6   * you may not use this file except in compliance with the License.
     7   * You may obtain a copy of the License at
     8   *
     9   *     http://www.apache.org/licenses/LICENSE-2.0
    10   *
    11   * Unless required by applicable law or agreed to in writing, software
    12   * distributed under the License is distributed on an "AS IS" BASIS,
    13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    14   * See the License for the specific language governing permissions and
    15   * limitations under the License.
    16   *
    17   */
    18  
    19  package testutils
    20  
    21  import (
    22  	"fmt"
    23  	"sync"
    24  
    25  	"github.com/hxx258456/ccgo/grpc/internal/wrr"
    26  )
    27  
    28  // testWRR is a deterministic WRR implementation.
    29  //
    30  // The real implementation does random WRR. testWRR makes the balancer behavior
    31  // deterministic and easier to test.
    32  //
    33  // With {a: 2, b: 3}, the Next() results will be {a, a, b, b, b}.
    34  type testWRR struct {
    35  	itemsWithWeight []struct {
    36  		item   interface{}
    37  		weight int64
    38  	}
    39  	length int
    40  
    41  	mu    sync.Mutex
    42  	idx   int   // The index of the item that will be picked
    43  	count int64 // The number of times the current item has been picked.
    44  }
    45  
    46  // NewTestWRR return a WRR for testing. It's deterministic instead of random.
    47  func NewTestWRR() wrr.WRR {
    48  	return &testWRR{}
    49  }
    50  
    51  func (twrr *testWRR) Add(item interface{}, weight int64) {
    52  	twrr.itemsWithWeight = append(twrr.itemsWithWeight, struct {
    53  		item   interface{}
    54  		weight int64
    55  	}{item: item, weight: weight})
    56  	twrr.length++
    57  }
    58  
    59  func (twrr *testWRR) Next() interface{} {
    60  	twrr.mu.Lock()
    61  	iww := twrr.itemsWithWeight[twrr.idx]
    62  	twrr.count++
    63  	if twrr.count >= iww.weight {
    64  		twrr.idx = (twrr.idx + 1) % twrr.length
    65  		twrr.count = 0
    66  	}
    67  	twrr.mu.Unlock()
    68  	return iww.item
    69  }
    70  
    71  func (twrr *testWRR) String() string {
    72  	return fmt.Sprint(twrr.itemsWithWeight)
    73  }