etcdctlv3: Add option to defrag a data directory directly, for cases …

…where etcd is not running.

etcdctl/ctlv3/command/defrag_command.go

@@ -17,20 +17,38 @@ package command
 import (
 	"fmt"
 	"os"
+	"path/filepath"
+	"time"
 
+	"github.com/coreos/etcd/mvcc/backend"
 	"github.com/spf13/cobra"
 )
 
+var (
+	defragDataDir string
+)
+
 // NewDefragCommand returns the cobra command for "Defrag".
 func NewDefragCommand() *cobra.Command {
-	return &cobra.Command{
+	cmd := &cobra.Command{
 		Use:   "defrag",
 		Short: "Defragments the storage of the etcd members with given endpoints",
 		Run:   defragCommandFunc,
 	}
+	cmd.Flags().StringVar(&defragDataDir, "data-dir", "", "Optional. If present, defragments a data directory not in use by etcd.")
+	return cmd
 }
 
 func defragCommandFunc(cmd *cobra.Command, args []string) {
+	if len(defragDataDir) > 0 {
+		err := defragData(defragDataDir)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "Failed to defragment etcd data[%s] (%v)\n", defragDataDir, err)
+			os.Exit(ExitError)
+		}
+		return
+	}
+
 	failures := 0
 	c := mustClientFromCmd(cmd)
 	for _, ep := range c.Endpoints() {
@@ -49,3 +67,23 @@ func defragCommandFunc(cmd *cobra.Command, args []string) {
 		os.Exit(ExitError)
 	}
 }
+
+func defragData(dataDir string) error {
+	var be backend.Backend
+
+	bch := make(chan struct{})
+	dbDir := filepath.Join(dataDir, "member", "snap", "db")
+	go func() {
+		defer close(bch)
+		be = backend.NewDefaultBackend(dbDir)
+
+	}()
+	select {
+	case <-bch:
+	case <-time.After(time.Second):
+		fmt.Fprintf(os.Stderr, "waiting for etcd to close and release its lock on %q. "+
+			"To defrag a running etcd instance, omit --data-dir.\n", dbDir)
+		<-bch
+	}
+	return be.Defrag()
+}