mirror of
https://github.com/etcd-io/etcd.git
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91 lines
2.2 KiB
Go
91 lines
2.2 KiB
Go
// Copyright 2017 The etcd 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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package concurrency_test
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import (
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"context"
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"fmt"
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"log"
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"sync"
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"time"
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"github.com/coreos/etcd/clientv3"
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"github.com/coreos/etcd/clientv3/concurrency"
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)
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func ExampleElection_Campaign() {
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cli, err := clientv3.New(clientv3.Config{Endpoints: endpoints})
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if err != nil {
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log.Fatal(err)
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}
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defer cli.Close()
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// create two separate sessions for election competition
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s1, err := concurrency.NewSession(cli)
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if err != nil {
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log.Fatal(err)
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}
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defer s1.Close()
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e1 := concurrency.NewElection(s1, "/my-election/")
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s2, err := concurrency.NewSession(cli)
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if err != nil {
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log.Fatal(err)
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}
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defer s2.Close()
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e2 := concurrency.NewElection(s2, "/my-election/")
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// create competing candidates, with e1 initially losing to e2
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var wg sync.WaitGroup
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wg.Add(2)
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electc := make(chan *concurrency.Election, 2)
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go func() {
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defer wg.Done()
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// delay candidacy so e2 wins first
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time.Sleep(3 * time.Second)
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if err := e1.Campaign(context.Background(), "e1"); err != nil {
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log.Fatal(err)
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}
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electc <- e1
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}()
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go func() {
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defer wg.Done()
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if err := e2.Campaign(context.Background(), "e2"); err != nil {
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log.Fatal(err)
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}
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electc <- e2
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}()
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cctx, cancel := context.WithCancel(context.TODO())
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defer cancel()
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e := <-electc
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fmt.Println("completed first election with", string((<-e.Observe(cctx)).Kvs[0].Value))
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// resign so next candidate can be elected
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if err := e.Resign(context.TODO()); err != nil {
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log.Fatal(err)
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}
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e = <-electc
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fmt.Println("completed second election with", string((<-e.Observe(cctx)).Kvs[0].Value))
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wg.Wait()
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// Output:
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// completed first election with e2
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// completed second election with e1
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}
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