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// 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 command
import (
"context"
"errors"
"fmt"
"os"
"os/exec"
"os/signal"
"syscall"
"go.etcd.io/etcd/client/v3"
"go.etcd.io/etcd/client/v3/concurrency"
"go.etcd.io/etcd/pkg/v3/cobrautl"
"github.com/spf13/cobra"
)
var lockTTL = 10
// NewLockCommand returns the cobra command for "lock".
func NewLockCommand() *cobra.Command {
c := &cobra.Command{
Use: "lock <lockname> [exec-command arg1 arg2 ...]",
Short: "Acquires a named lock",
Run: lockCommandFunc,
}
c.Flags().IntVarP(&lockTTL, "ttl", "", lockTTL, "timeout for session")
return c
}
func lockCommandFunc(cmd *cobra.Command, args []string) {
if len(args) == 0 {
cobrautl.ExitWithError(cobrautl.ExitBadArgs, errors.New("lock takes a lock name argument and an optional command to execute"))
}
c := mustClientFromCmd(cmd)
if err := lockUntilSignal(c, args[0], args[1:]); err != nil {
code := getExitCodeFromError(err)
cobrautl.ExitWithError(code, err)
}
}
func getExitCodeFromError(err error) int {
if err == nil {
return cobrautl.ExitSuccess
}
if exitErr, ok := err.(*exec.ExitError); ok {
if status, ok := exitErr.Sys().(syscall.WaitStatus); ok {
return status.ExitStatus()
}
}
return cobrautl.ExitError
}
func lockUntilSignal(c *clientv3.Client, lockname string, cmdArgs []string) error {
s, err := concurrency.NewSession(c, concurrency.WithTTL(lockTTL))
if err != nil {
return err
}
m := concurrency.NewMutex(s, lockname)
ctx, cancel := context.WithCancel(context.TODO())
// unlock in case of ordinary shutdown
donec := make(chan struct{})
sigc := make(chan os.Signal, 1)
signal.Notify(sigc, syscall.SIGINT, syscall.SIGTERM)
go func() {
<-sigc
cancel()
close(donec)
}()
if err := m.Lock(ctx); err != nil {
return err
}
if len(cmdArgs) > 0 {
cmd := exec.Command(cmdArgs[0], cmdArgs[1:]...)
cmd.Env = append(environLockResponse(m), os.Environ()...)
cmd.Stdout, cmd.Stderr = os.Stdout, os.Stderr
err := cmd.Run()
unlockErr := m.Unlock(context.TODO())
if err != nil {
return err
}
return unlockErr
}
k, kerr := c.Get(ctx, m.Key())
if kerr != nil {
return kerr
}
if len(k.Kvs) == 0 {
return errors.New("lock lost on init")
}
display.Get(*k)
select {
case <-donec:
return m.Unlock(context.TODO())
case <-s.Done():
}
return errors.New("session expired")
}
func environLockResponse(m *concurrency.Mutex) []string {
return []string{
"ETCD_LOCK_KEY=" + m.Key(),
fmt.Sprintf("ETCD_LOCK_REV=%d", m.Header().Revision),
}
}
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