mirror of
https://github.com/etcd-io/etcd.git
synced 2024-09-27 06:25:44 +00:00
139 lines
3.1 KiB
Go
139 lines
3.1 KiB
Go
// Copyright 2016 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 command
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import (
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"context"
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"errors"
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"os"
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"os/signal"
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"syscall"
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"github.com/spf13/cobra"
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clientv3 "go.etcd.io/etcd/client/v3"
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"go.etcd.io/etcd/client/v3/concurrency"
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"go.etcd.io/etcd/pkg/v3/cobrautl"
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)
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var (
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electListen bool
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)
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// NewElectCommand returns the cobra command for "elect".
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func NewElectCommand() *cobra.Command {
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cmd := &cobra.Command{
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Use: "elect <election-name> [proposal]",
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Short: "Observes and participates in leader election",
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Run: electCommandFunc,
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}
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cmd.Flags().BoolVarP(&electListen, "listen", "l", false, "observation mode")
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return cmd
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}
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func electCommandFunc(cmd *cobra.Command, args []string) {
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if len(args) != 1 && len(args) != 2 {
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cobrautl.ExitWithError(cobrautl.ExitBadArgs, errors.New("elect takes one election name argument and an optional proposal argument"))
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}
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c := mustClientFromCmd(cmd)
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var err error
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if len(args) == 1 {
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if !electListen {
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cobrautl.ExitWithError(cobrautl.ExitBadArgs, errors.New("no proposal argument but -l not set"))
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}
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err = observe(c, args[0])
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} else {
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if electListen {
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cobrautl.ExitWithError(cobrautl.ExitBadArgs, errors.New("proposal given but -l is set"))
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}
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err = campaign(c, args[0], args[1])
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}
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if err != nil {
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cobrautl.ExitWithError(cobrautl.ExitError, err)
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}
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}
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func observe(c *clientv3.Client, election string) error {
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s, err := concurrency.NewSession(c)
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if err != nil {
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return err
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}
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e := concurrency.NewElection(s, election)
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ctx, cancel := context.WithCancel(context.TODO())
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donec := make(chan struct{})
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sigc := make(chan os.Signal, 1)
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signal.Notify(sigc, syscall.SIGINT, syscall.SIGTERM)
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go func() {
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<-sigc
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cancel()
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}()
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go func() {
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for resp := range e.Observe(ctx) {
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display.Get(resp)
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}
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close(donec)
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}()
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<-donec
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select {
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case <-ctx.Done():
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default:
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return errors.New("elect: observer lost")
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}
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return nil
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}
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func campaign(c *clientv3.Client, election string, prop string) error {
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s, err := concurrency.NewSession(c)
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if err != nil {
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return err
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}
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e := concurrency.NewElection(s, election)
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ctx, cancel := context.WithCancel(context.TODO())
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donec := make(chan struct{})
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sigc := make(chan os.Signal, 1)
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signal.Notify(sigc, syscall.SIGINT, syscall.SIGTERM)
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go func() {
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<-sigc
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cancel()
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close(donec)
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}()
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if err = e.Campaign(ctx, prop); err != nil {
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return err
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}
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// print key since elected
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resp, err := c.Get(ctx, e.Key())
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if err != nil {
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return err
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}
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display.Get(*resp)
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select {
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case <-donec:
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case <-s.Done():
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return errors.New("elect: session expired")
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}
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return e.Resign(context.TODO())
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}
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