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lock_command.go
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lock_command.go
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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 (
"errors"
"os"
"os/signal"
"github.com/coreos/etcd/clientv3"
"github.com/coreos/etcd/clientv3/concurrency"
"github.com/spf13/cobra"
"golang.org/x/net/context"
)
// NewLockCommand returns the cobra command for "lock".
func NewLockCommand() *cobra.Command {
c := &cobra.Command{
Use: "lock <lockname>",
Short: "Acquires a named lock",
Run: lockCommandFunc,
}
return c
}
func lockCommandFunc(cmd *cobra.Command, args []string) {
if len(args) != 1 {
ExitWithError(ExitBadArgs, errors.New("lock takes one lock name arguement."))
}
c := mustClientFromCmd(cmd)
if err := lockUntilSignal(c, args[0]); err != nil {
ExitWithError(ExitError, err)
}
}
func lockUntilSignal(c *clientv3.Client, lockname string) error {
m := concurrency.NewMutex(c, 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, os.Interrupt, os.Kill)
go func() {
<-sigc
cancel()
close(donec)
}()
s, serr := concurrency.NewSession(c)
if serr != nil {
return serr
}
if err := m.Lock(ctx); err != nil {
return err
}
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")
}