snapshot of https://github.com/grpc/grpc-go.git (master, 2026-09-15; blobs > 131072B omitted)

internal/testutils/wrr.go

@@ -0,0 +1,73 @@
+/*
+ *
+ * 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   any
+		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 any, weight int64) {
+	twrr.itemsWithWeight = append(twrr.itemsWithWeight, struct {
+		item   any
+		weight int64
+	}{item: item, weight: weight})
+	twrr.length++
+}
+
+func (twrr *testWRR) Next() any {
+	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)
+}