mirror of
https://github.com/etcd-io/etcd.git
synced 2024-09-27 06:25:44 +00:00
130 lines
3.0 KiB
Go
130 lines
3.0 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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"fmt"
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"os"
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"os/exec"
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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 lockTTL = 10
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// NewLockCommand returns the cobra command for "lock".
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func NewLockCommand() *cobra.Command {
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c := &cobra.Command{
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Use: "lock <lockname> [exec-command arg1 arg2 ...]",
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Short: "Acquires a named lock",
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Run: lockCommandFunc,
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}
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c.Flags().IntVarP(&lockTTL, "ttl", "", lockTTL, "timeout for session")
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return c
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}
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func lockCommandFunc(cmd *cobra.Command, args []string) {
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if len(args) == 0 {
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cobrautl.ExitWithError(cobrautl.ExitBadArgs, errors.New("lock takes a lock name argument and an optional command to execute"))
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}
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c := mustClientFromCmd(cmd)
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if err := lockUntilSignal(c, args[0], args[1:]); err != nil {
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code := getExitCodeFromError(err)
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cobrautl.ExitWithError(code, err)
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}
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}
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func getExitCodeFromError(err error) int {
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if err == nil {
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return cobrautl.ExitSuccess
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}
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if exitErr, ok := err.(*exec.ExitError); ok {
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if status, ok := exitErr.Sys().(syscall.WaitStatus); ok {
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return status.ExitStatus()
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}
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}
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return cobrautl.ExitError
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}
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func lockUntilSignal(c *clientv3.Client, lockname string, cmdArgs []string) error {
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s, err := concurrency.NewSession(c, concurrency.WithTTL(lockTTL))
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if err != nil {
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return err
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}
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m := concurrency.NewMutex(s, lockname)
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ctx, cancel := context.WithCancel(context.TODO())
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// unlock in case of ordinary shutdown
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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 := m.Lock(ctx); err != nil {
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return err
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}
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if len(cmdArgs) > 0 {
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cmd := exec.Command(cmdArgs[0], cmdArgs[1:]...)
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cmd.Env = append(environLockResponse(m), os.Environ()...)
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cmd.Stdout, cmd.Stderr = os.Stdout, os.Stderr
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err := cmd.Run()
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unlockErr := m.Unlock(context.TODO())
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if err != nil {
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return err
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}
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return unlockErr
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}
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k, kerr := c.Get(ctx, m.Key())
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if kerr != nil {
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return kerr
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}
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if len(k.Kvs) == 0 {
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return errors.New("lock lost on init")
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}
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display.Get(*k)
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select {
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case <-donec:
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return m.Unlock(context.TODO())
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case <-s.Done():
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}
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return errors.New("session expired")
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}
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func environLockResponse(m *concurrency.Mutex) []string {
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return []string{
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"ETCD_LOCK_KEY=" + m.Key(),
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fmt.Sprintf("ETCD_LOCK_REV=%d", m.Header().Revision),
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}
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}
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