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

internal/balancer/stub/stub.go

@@ -0,0 +1,116 @@
+/*
+ *
+ * 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 stub implements a balancer for testing purposes.
+package stub
+
+import (
+	"encoding/json"
+	"fmt"
+
+	"google.golang.org/grpc/balancer"
+	"google.golang.org/grpc/serviceconfig"
+)
+
+// BalancerFuncs contains all balancer.Balancer functions with a preceding
+// *BalancerData parameter for passing additional instance information.  Any
+// nil functions will never be called.
+type BalancerFuncs struct {
+	// Init is called after ClientConn and BuildOptions are set in
+	// BalancerData.  It may be used to initialize BalancerData.Data.
+	Init func(*BalancerData)
+	// ParseConfig is used for parsing LB configs, if specified.
+	ParseConfig func(json.RawMessage) (serviceconfig.LoadBalancingConfig, error)
+
+	UpdateClientConnState func(*BalancerData, balancer.ClientConnState) error
+	ResolverError         func(*BalancerData, error)
+	Close                 func(*BalancerData)
+	ExitIdle              func(*BalancerData)
+}
+
+// BalancerData contains data relevant to a stub balancer.
+type BalancerData struct {
+	// ClientConn is set by the builder.
+	ClientConn balancer.ClientConn
+	// BuildOptions is set by the builder.
+	BuildOptions balancer.BuildOptions
+	// ChildBalancer holds a child balancer.
+	ChildBalancer balancer.Balancer
+}
+
+type bal struct {
+	bf BalancerFuncs
+	bd *BalancerData
+}
+
+func (b *bal) UpdateClientConnState(c balancer.ClientConnState) error {
+	if b.bf.UpdateClientConnState != nil {
+		return b.bf.UpdateClientConnState(b.bd, c)
+	}
+	return nil
+}
+
+func (b *bal) ResolverError(e error) {
+	if b.bf.ResolverError != nil {
+		b.bf.ResolverError(b.bd, e)
+	}
+}
+
+func (b *bal) UpdateSubConnState(sc balancer.SubConn, scs balancer.SubConnState) {
+	panic(fmt.Sprintf("UpdateSubConnState(%v, %+v) called unexpectedly", sc, scs))
+}
+
+func (b *bal) Close() {
+	if b.bf.Close != nil {
+		b.bf.Close(b.bd)
+	}
+}
+
+func (b *bal) ExitIdle() {
+	if b.bf.ExitIdle != nil {
+		b.bf.ExitIdle(b.bd)
+	}
+}
+
+type bb struct {
+	name string
+	bf   BalancerFuncs
+}
+
+func (bb bb) Build(cc balancer.ClientConn, opts balancer.BuildOptions) balancer.Balancer {
+	b := &bal{bf: bb.bf, bd: &BalancerData{ClientConn: cc, BuildOptions: opts}}
+	if b.bf.Init != nil {
+		b.bf.Init(b.bd)
+	}
+	return b
+}
+
+func (bb bb) Name() string { return bb.name }
+
+func (bb bb) ParseConfig(lbCfg json.RawMessage) (serviceconfig.LoadBalancingConfig, error) {
+	if bb.bf.ParseConfig != nil {
+		return bb.bf.ParseConfig(lbCfg)
+	}
+	return nil, nil
+}
+
+// Register registers a stub balancer builder which will call the provided
+// functions.  The name used should be unique.
+func Register(name string, bf BalancerFuncs) {
+	balancer.Register(bb{name: name, bf: bf})
+}