tests/integration: Move of naming/snapshot clientv3 tests (and yaml reference)

path change in clientv3/yaml/config_test

git mv clientv3/naming/grpc_test.go         tests/integration/clientv3/grpc_test.go
git mv clientv3/snapshot/*_test.go          tests/integration/snapshot
git mv clientv3/{main_test.go,example_*.go} tests/integration/clientv3/examples/

tests/integration/clientv3/examples/example_metrics_test.go

@@ -0,0 +1,85 @@
+// Copyright 2016 The etcd 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 clientv3_test
+
+import (
+	"context"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"net"
+	"net/http"
+	"strings"
+
+	"go.etcd.io/etcd/v3/clientv3"
+
+	grpcprom "github.com/grpc-ecosystem/go-grpc-prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+	"google.golang.org/grpc"
+)
+
+func ExampleClient_metrics() {
+	cli, err := clientv3.New(clientv3.Config{
+		Endpoints: endpoints,
+		DialOptions: []grpc.DialOption{
+			grpc.WithUnaryInterceptor(grpcprom.UnaryClientInterceptor),
+			grpc.WithStreamInterceptor(grpcprom.StreamClientInterceptor),
+		},
+	})
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer cli.Close()
+
+	// get a key so it shows up in the metrics as a range RPC
+	cli.Get(context.TODO(), "test_key")
+
+	// listen for all Prometheus metrics
+	ln, err := net.Listen("tcp", ":0")
+	if err != nil {
+		log.Fatal(err)
+	}
+	donec := make(chan struct{})
+	go func() {
+		defer close(donec)
+		http.Serve(ln, promhttp.Handler())
+	}()
+	defer func() {
+		ln.Close()
+		<-donec
+	}()
+
+	// make an http request to fetch all Prometheus metrics
+	url := "http://" + ln.Addr().String() + "/metrics"
+	resp, err := http.Get(url)
+	if err != nil {
+		log.Fatalf("fetch error: %v", err)
+	}
+	b, err := ioutil.ReadAll(resp.Body)
+	resp.Body.Close()
+	if err != nil {
+		log.Fatalf("fetch error: reading %s: %v", url, err)
+	}
+
+	// confirm range request in metrics
+	for _, l := range strings.Split(string(b), "\n") {
+		if strings.Contains(l, `grpc_client_started_total{grpc_method="Range"`) {
+			fmt.Println(l)
+			break
+		}
+	}
+	// Output:
+	//	grpc_client_started_total{grpc_method="Range",grpc_service="etcdserverpb.KV",grpc_type="unary"} 1
+}