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/*
*
* Copyright 2020 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 testutils
import (
"fmt"
"sync"
"google.golang.org/grpc/internal/wrr"
)
// testWRR is a deterministic WRR implementation.
//
// The real implementation does random WRR. testWRR makes the balancer behavior
// deterministic and easier to test.
//
// With {a: 2, b: 3}, the Next() results will be {a, a, b, b, b}.
type testWRR struct {
itemsWithWeight []struct {
item interface{}
weight int64
}
length int
mu sync.Mutex
idx int // The index of the item that will be picked
count int64 // The number of times the current item has been picked.
}
// NewTestWRR return a WRR for testing. It's deterministic instead of random.
func NewTestWRR() wrr.WRR {
return &testWRR{}
}
func (twrr *testWRR) Add(item interface{}, weight int64) {
twrr.itemsWithWeight = append(twrr.itemsWithWeight, struct {
item interface{}
weight int64
}{item: item, weight: weight})
twrr.length++
}
func (twrr *testWRR) Next() interface{} {
twrr.mu.Lock()
iww := twrr.itemsWithWeight[twrr.idx]
twrr.count++
if twrr.count >= iww.weight {
twrr.idx = (twrr.idx + 1) % twrr.length
twrr.count = 0
}
twrr.mu.Unlock()
return iww.item
}
func (twrr *testWRR) String() string {
return fmt.Sprint(twrr.itemsWithWeight)
}
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