mirror of https://github.com/grpc/grpc-go.git
128 lines
3.6 KiB
Go
128 lines
3.6 KiB
Go
/*
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*
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* Copyright 2018 gRPC authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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*/
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// Binary client demonstrates how to configure load balancing policies to
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// distribute RPCs across backend servers.
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package main
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import (
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"context"
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"fmt"
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"log"
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"time"
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"google.golang.org/grpc"
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"google.golang.org/grpc/credentials/insecure"
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ecpb "google.golang.org/grpc/examples/features/proto/echo"
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"google.golang.org/grpc/resolver"
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)
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const (
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exampleScheme = "example"
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exampleServiceName = "lb.example.grpc.io"
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)
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var addrs = []string{"localhost:50051", "localhost:50052"}
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func callUnaryEcho(c ecpb.EchoClient, message string) {
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ctx, cancel := context.WithTimeout(context.Background(), time.Second)
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defer cancel()
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r, err := c.UnaryEcho(ctx, &ecpb.EchoRequest{Message: message})
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if err != nil {
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log.Fatalf("could not greet: %v", err)
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}
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fmt.Println(r.Message)
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}
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func makeRPCs(cc *grpc.ClientConn, n int) {
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hwc := ecpb.NewEchoClient(cc)
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for i := 0; i < n; i++ {
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callUnaryEcho(hwc, "this is examples/load_balancing")
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}
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}
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func main() {
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// "pick_first" is the default, so there's no need to set the load balancing policy.
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pickfirstConn, err := grpc.NewClient(
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fmt.Sprintf("%s:///%s", exampleScheme, exampleServiceName),
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grpc.WithTransportCredentials(insecure.NewCredentials()),
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)
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if err != nil {
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log.Fatalf("did not connect: %v", err)
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}
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defer pickfirstConn.Close()
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fmt.Println("--- calling helloworld.Greeter/SayHello with pick_first ---")
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makeRPCs(pickfirstConn, 10)
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fmt.Println()
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// Make another ClientConn with round_robin policy.
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roundrobinConn, err := grpc.NewClient(
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fmt.Sprintf("%s:///%s", exampleScheme, exampleServiceName),
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grpc.WithDefaultServiceConfig(`{"loadBalancingConfig": [{"round_robin":{}}]}`), // This sets the initial balancing policy.
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grpc.WithTransportCredentials(insecure.NewCredentials()),
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)
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if err != nil {
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log.Fatalf("did not connect: %v", err)
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}
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defer roundrobinConn.Close()
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fmt.Println("--- calling helloworld.Greeter/SayHello with round_robin ---")
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makeRPCs(roundrobinConn, 10)
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}
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// Following is an example name resolver implementation. Read the name
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// resolution example to learn more about it.
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type exampleResolverBuilder struct{}
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func (*exampleResolverBuilder) Build(target resolver.Target, cc resolver.ClientConn, _ resolver.BuildOptions) (resolver.Resolver, error) {
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r := &exampleResolver{
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target: target,
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cc: cc,
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addrsStore: map[string][]string{
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exampleServiceName: addrs,
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},
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}
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r.start()
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return r, nil
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}
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func (*exampleResolverBuilder) Scheme() string { return exampleScheme }
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type exampleResolver struct {
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target resolver.Target
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cc resolver.ClientConn
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addrsStore map[string][]string
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}
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func (r *exampleResolver) start() {
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addrStrs := r.addrsStore[r.target.Endpoint()]
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addrs := make([]resolver.Address, len(addrStrs))
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for i, s := range addrStrs {
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addrs[i] = resolver.Address{Addr: s}
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}
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r.cc.UpdateState(resolver.State{Addresses: addrs})
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}
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func (*exampleResolver) ResolveNow(resolver.ResolveNowOptions) {}
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func (*exampleResolver) Close() {}
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func init() {
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resolver.Register(&exampleResolverBuilder{})
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}
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