Improve logging and error messages for fallback

Author: boris-ilijic

cmd/pbm/backup.go

@@ -341,7 +341,7 @@ type bcpReplDesc struct {
 	Node               string              `json:"node" yaml:"node"`
 	Files              []backup.File       `json:"files,omitempty" yaml:"-"`
 	Size               int64               `json:"size" yaml:"-"`
-	HSize              string              `json:"size_h" yaml:"size_h"`
+	HSize              string              `json:"size_h,omitempty" yaml:"size_h,omitempty"`
 	LastWriteTS        int64               `json:"last_write_ts" yaml:"-"`
 	LastTransitionTS   int64               `json:"last_transition_ts" yaml:"-"`
 	LastWriteTime      string              `json:"last_write_time" yaml:"last_write_time"`
@@ -445,7 +445,6 @@ func describeBackup(
 			IsConfigShard:      r.IsConfigShard,
 			Status:             r.Status,
 			Size:               r.Size,
-			HSize:              byteCountIEC(r.Size),
 			LastWriteTS:        int64(r.LastWriteTS.T),
 			LastTransitionTS:   r.LastTransitionTS,
 			LastWriteTime:      time.Unix(int64(r.LastWriteTS.T), 0).UTC().Format(time.RFC3339),
@@ -461,6 +460,9 @@ func describeBackup(
 		if bcp.Type == defs.ExternalBackup {
 			rv.Replsets[i].Files = r.Files
 		}
+		if r.Size > 0 {
+			rv.Replsets[i].HSize = byteCountIEC(r.Size)
+		}
 
 		if !b.coll || bcp.Type != defs.LogicalBackup {
 			continue

cmd/pbm/main.go

@@ -810,12 +810,12 @@ func (app *pbmApp) buildRestoreCmd() *cobra.Command {
 	)
 	restoreCmd.Flags().BoolVar(
 		&restoreOptions.fallback, "fallback-enabled", true,
-		"Disables fallback sync feature when doing physical restore. Enabled by default.",
+		"Enables/disables fallback strategy when doing physical restore.",
 	)
 	restoreCmd.Flags().BoolVar(
 		&restoreOptions.allowPartlyDone, "allow-partly-done", true,
 		"Allows parly done state of the cluster after physical restore. "+
-			"If disabled, fallback will be applied when cluster is partly-done. Enabled by default.",
+			"If disabled, fallback will be applied when cluster is partly-done.",
 	)
 
 	restoreCmd.Flags().StringVar(&restoreOptions.rsMap, RSMappingFlag, "", RSMappingDoc)

pbm/restore/physical.go

@@ -2548,11 +2548,12 @@ func (r *PhysRestore) prepareBackup(ctx context.Context, backupName string) erro
 
 	setName := mapRevRS(r.nodeInfo.SetName)
 
+	r.log.Debug("restore opts: --fallback-enabled: %t; --allow-partly-done: %t",
+		r.fallback, r.allowPartlyDone)
 	if r.fallback && r.bcp.RS(setName) != nil {
 		err = r.checkDiskSpace(r.bcp.RS(setName).Size)
 		if err != nil {
-			return errors.Wrap(err, "not enough disk space for fallback strategy, "+
-				"consider using --fallback-enabled=false")
+			return errors.Wrap(err, "check disk space")
 		}
 	}
 
@@ -2607,6 +2608,11 @@ func (r *PhysRestore) checkMongod(needVersion string) (version string, err error
 // It returns error in case when backup size is larger than free space on the disk.
 // It also includes min disk space requirement of 10GiB.
 func (r *PhysRestore) checkDiskSpace(bcpSize int64) error {
+	if bcpSize == 0 {
+		return errors.New("unable to apply fallback strategy for unknown backup size, " +
+			"consider using --fallback-enabled=false")
+	}
+
 	var stat syscall.Statfs_t
 	err := syscall.Statfs(r.dbpath, &stat)
 	if err != nil {
@@ -2615,8 +2621,13 @@ func (r *PhysRestore) checkDiskSpace(bcpSize int64) error {
 
 	free := int64(stat.Bavail) * int64(stat.Bsize)
 	tenGiB := 10 * (1 << 30)
-	if bcpSize+int64(tenGiB) >= free {
-		return errors.Errorf("not enough disk space, free=%d, backup size=%d", free, bcpSize)
+	totalReqSize := bcpSize + int64(tenGiB)
+	r.log.Debug("free space on disk: %s; backup size: %s; total requested free size: %s",
+		storage.PrettySize(free), storage.PrettySize(bcpSize), storage.PrettySize(totalReqSize))
+
+	if totalReqSize >= free {
+		return errors.New("not enough disk space for fallback strategy, " +
+			"consider using --fallback-enabled=false")
 	}
 
 	return nil