Add exit code log and possible memory shortage warning log for Restic…

… command failure.

Signed-off-by: Xun Jiang <[email protected]>

changelogs/unreleased/6459-blackpiglet

@@ -0,0 +1 @@
+Add exit code log and possible memory shortage warning log for Restic command failure.

pkg/repository/restic/repository.go

@@ -18,6 +18,7 @@ package restic
 
 import (
 	"os"
+	"os/exec"
 	"time"
 
 	"github.com/pkg/errors"
@@ -120,6 +121,17 @@ func (r *RepositoryService) exec(cmd *restic.Command, bsl *velerov1api.BackupSto
 		"stderr":     stderr,
 	}).Debugf("Ran restic command")
 	if err != nil {
+		if exitError, ok := err.(*exec.ExitError); ok {
+			r.log.Errorf("Restic command fail with ExitCode: %d. Process ID is %d, Exit error is: %s", exitError.ExitCode(), exitError.Pid(), exitError.String())
+			// Golang's os.exec -1 ExitCode means signal kill. Usually this is caused
+			// by CGroup's OOM. Log a warning to notice user.
+			// https://github.com/golang/go/blob/master/src/os/exec_posix.go#L128-L136
+			if exitError.ExitCode() == -1 {
+				r.log.Warnf("The ExitCode is -1, which means the process is terminated by signal. Usually this is caused by CGroup kill due to out of memory. Please check whether this is such information in the work nodes' dmesg log.")
+			}
+		} else {
+			r.log.Error("Error cannot be convert to ExitError format")
+		}
 		return errors.Wrapf(err, "error running command=%s, stdout=%s, stderr=%s", cmd.String(), stdout, stderr)
 	}