| // 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" |
| |
| "github.com/coreos/etcd/clientv3" |
| "github.com/coreos/etcd/clientv3/concurrency" |
| |
| "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 { |
| ExitWithError(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 { |
| ExitWithError(ExitError, err) |
| } |
| } |
| |
| 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), |
| } |
| } |