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/*
*
* Copyright 2018 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.
*
*/
// Binary client is an example client.
package main
import (
"context"
"fmt"
"log"
"time"
"google.golang.org/grpc"
ecpb "google.golang.org/grpc/examples/features/proto/echo"
"google.golang.org/grpc/resolver"
)
const (
exampleScheme = "example"
exampleServiceName = "lb.example.grpc.io"
)
var addrs = []string{"localhost:50051", "localhost:50052"}
func callUnaryEcho(c ecpb.EchoClient, message string) {
ctx, cancel := context.WithTimeout(context.Background(), time.Second)
defer cancel()
r, err := c.UnaryEcho(ctx, &ecpb.EchoRequest{Message: message})
if err != nil {
log.Fatalf("could not greet: %v", err)
}
fmt.Println(r.Message)
}
func makeRPCs(cc *grpc.ClientConn, n int) {
hwc := ecpb.NewEchoClient(cc)
for i := 0; i < n; i++ {
callUnaryEcho(hwc, "this is examples/load_balancing")
}
}
func main() {
// "pick_first" is the default, so there's no need to set the load balancer.
pickfirstConn, err := grpc.Dial(
fmt.Sprintf("%s:///%s", exampleScheme, exampleServiceName),
grpc.WithInsecure(),
grpc.WithBlock(),
)
if err != nil {
log.Fatalf("did not connect: %v", err)
}
defer pickfirstConn.Close()
fmt.Println("--- calling helloworld.Greeter/SayHello with pick_first ---")
makeRPCs(pickfirstConn, 10)
fmt.Println()
// Make another ClientConn with round_robin policy.
roundrobinConn, err := grpc.Dial(
fmt.Sprintf("%s:///%s", exampleScheme, exampleServiceName),
grpc.WithDefaultServiceConfig(`{"loadBalancingPolicy":"round_robin"}`), // This sets the initial balancing policy.
grpc.WithInsecure(),
grpc.WithBlock(),
)
if err != nil {
log.Fatalf("did not connect: %v", err)
}
defer roundrobinConn.Close()
fmt.Println("--- calling helloworld.Greeter/SayHello with round_robin ---")
makeRPCs(roundrobinConn, 10)
}
// Following is an example name resolver implementation. Read the name
// resolution example to learn more about it.
type exampleResolverBuilder struct{}
func (*exampleResolverBuilder) Build(target resolver.Target, cc resolver.ClientConn, opts resolver.BuildOptions) (resolver.Resolver, error) {
r := &exampleResolver{
target: target,
cc: cc,
addrsStore: map[string][]string{
exampleServiceName: addrs,
},
}
r.start()
return r, nil
}
func (*exampleResolverBuilder) Scheme() string { return exampleScheme }
type exampleResolver struct {
target resolver.Target
cc resolver.ClientConn
addrsStore map[string][]string
}
func (r *exampleResolver) start() {
addrStrs := r.addrsStore[r.target.Endpoint]
addrs := make([]resolver.Address, len(addrStrs))
for i, s := range addrStrs {
addrs[i] = resolver.Address{Addr: s}
}
r.cc.UpdateState(resolver.State{Addresses: addrs})
}
func (*exampleResolver) ResolveNow(o resolver.ResolveNowOptions) {}
func (*exampleResolver) Close() {}
func init() {
resolver.Register(&exampleResolverBuilder{})
}
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