Backup snapshoting

main.go

@@ -35,11 +35,14 @@ import (
 )
 
 type ofsVolume struct {
-	Volume          *volume.Volume
-	Fs              string
-	Opts            string
-	Env             []string
-	Asap            bool
+	Volume *volume.Volume
+	Fs     string
+	Opts   string
+	Env    []string
+	Asap   bool
+	// Create a snaphot on each mount (and delete the previous one)
+	Backup          bool
+	BackupSnapshot  string
 	MountSnapshots  bool
 	SnapshotsFilter string
 }
@@ -103,6 +106,8 @@ func (d *ofsDriver) Create(r *volume.CreateRequest) error {
 			}
 		case "asap":
 			v.Asap = true
+		case "backup":
+			v.Backup = true
 		case "mountSnapshots":
 			v.MountSnapshots = val == "yes"
 		case "snapshotsFilter":
@@ -200,6 +205,15 @@ func umount(v *ofsVolume, rt *ofsVolumeRt) error {
 	if err := os.Remove(v.Volume.Mountpoint); err != nil {
 		return err
 	}
+
+	if v.Backup {
+		if err := applyEnv(exec.Command("/sbin/mount.objectivefs", "destroy", v.BackupSnapshot, "-f"), v.Env).Wait(); err == nil {
+			log.WithFields(log.Fields{"name": v.Volume.Name, "snapshot": v.BackupSnapshot}).Info("Failed to destroy the previous snapshot")
+			return err
+		}
+		v.BackupSnapshot = ""
+	}
+
 	rt.mounted = false
 	return nil
 }
@@ -276,17 +290,48 @@ func (d *ofsDriver) Mount(r *volume.MountRequest) (*volume.MountResponse, error)
 	}
 
 	log.WithFields(log.Fields{"name": r.Name, "id": r.ID}).Info("Attach ObjectiveFS Volume")
+
+	// Each mount request causes new snapshot to get created and the old one deleted
+	if v.Backup && rt.mounted {
+		log.WithFields(log.Fields{"name": r.Name, "snapshot": v.BackupSnapshot}).Info("Going to unmount and destroy the previous backup snapshot")
+		if err := umount(v, rt); err != nil {
+			return &volume.MountResponse{}, err
+		}
+	}
+
 	if !rt.mounted {
 		if err := os.MkdirAll(v.Volume.Mountpoint, 0755); err != nil {
 			return &volume.MountResponse{}, err
 		}
 
+		var fs string
+		if v.Backup {
+			log.WithFields(log.Fields{"name": r.Name}).Info("Going to create a backup snapshot")
+			if snapshotTextB, err := applyEnv(exec.Command("/sbin/mount.objectivefs", "snapshot", v.Fs), v.Env).CombinedOutput(); err == nil {
+				log.WithFields(log.Fields{"name": v.Volume.Name, "output": string(snapshotTextB[:])}).Info("Failed to create a new backup snapshot")
+				return &volume.MountResponse{}, err
+			} else {
+				// Format: NOTE: Successfully created snapshot: snapshotId (<current UTC time>)
+				const okPrefix = "NOTE: Successfully created snapshot:"
+				snapshotText := string(snapshotTextB[:])
+				if snapshotIdWithSuffix, isOk := strings.CutPrefix(snapshotText, okPrefix); !isOk {
+					log.WithFields(log.Fields{"name": v.Volume.Name, "snapshot": v.BackupSnapshot}).Info("Failed to create a new backup snapshot")
+					return &volume.MountResponse{}, err
+				} else {
+					v.BackupSnapshot = strings.SplitAfter(snapshotIdWithSuffix, " ")[0]
+					fs = v.BackupSnapshot
+				}
+			}
+		} else {
+			fs = v.Fs
+		}
+
 		// Note: The first argument ("mount") causes running in the foreground, its absence in the background
 		var cmd *exec.Cmd
 		if len(v.Opts) == 0 {
-			cmd = exec.Command("/sbin/mount.objectivefs", "mount", v.Fs, v.Volume.Mountpoint)
+			cmd = exec.Command("/sbin/mount.objectivefs", "mount", fs, v.Volume.Mountpoint)
 		} else {
-			cmd = exec.Command("/sbin/mount.objectivefs", "mount", "-o"+v.Opts, v.Fs, v.Volume.Mountpoint)
+			cmd = exec.Command("/sbin/mount.objectivefs", "mount", "-o"+v.Opts, fs, v.Volume.Mountpoint)
 		}
 
 		cmd.Env = v.Env