concurrency: add examples

clientv3/concurrency/example_mutex_test.go

@@ -0,0 +1,75 @@
+// Copyright 2017 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 concurrency_test
+
+import (
+	"context"
+	"fmt"
+	"log"
+
+	"github.com/coreos/etcd/clientv3"
+	"github.com/coreos/etcd/clientv3/concurrency"
+)
+
+func ExampleMutex_Lock() {
+	cli, err := clientv3.New(clientv3.Config{Endpoints: endpoints})
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer cli.Close()
+
+	// create two separate sessions for lock competition
+	s1, err := concurrency.NewSession(cli)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer s1.Close()
+	m1 := concurrency.NewMutex(s1, "/my-lock/")
+
+	s2, err := concurrency.NewSession(cli)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer s2.Close()
+	m2 := concurrency.NewMutex(s2, "/my-lock/")
+
+	// acquire lock for s1
+	if err := m1.Lock(context.TODO()); err != nil {
+		log.Fatal(err)
+	}
+	fmt.Println("acquired lock for s1")
+
+	m2Locked := make(chan struct{})
+	go func() {
+		defer close(m2Locked)
+		// wait until s1 is locks /my-lock/
+		if err := m2.Lock(context.TODO()); err != nil {
+			log.Fatal(err)
+		}
+	}()
+
+	if err := m1.Unlock(context.TODO()); err != nil {
+		log.Fatal(err)
+	}
+	fmt.Println("released lock for s1")
+
+	<-m2Locked
+	fmt.Println("acquired lock for s2")
+
+	// Output:
+	// acquired lock for s1
+	// released lock for s1
+	// acquired lock for s2
+}