feat: return proper gRPC error codes for expected conditions (#549)

The plugin now returns a 404 status code when a requested WAL file does
not exist in the object store.

This prevents misleading log entries such as "Error while handling gRPC
request" for expected missing-file scenarios.

The `ErrEndOfWALStreamReached` now returns `OutOfRange` error.

The `ErrMissingPermissions` now returns `FailedPrecondition` error.

Signed-off-by: Leonardo Cecchi <[email protected]>
Signed-off-by: Armando Ruocco <[email protected]>
Signed-off-by: Marco Nenciarini <[email protected]>
Co-authored-by: Armando Ruocco <[email protected]>
Co-authored-by: Marco Nenciarini <[email protected]>

Author: 3 people

internal/cnpgi/common/errors.go

@@ -1,16 +1,25 @@
 package common
 
-// walNotFoundError is raised when a WAL file has not been found in the object store
-type walNotFoundError struct{}
+import (
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
+)
 
-func newWALNotFoundError() *walNotFoundError { return &walNotFoundError{} }
+// ErrEndOfWALStreamReached is returned when end of WAL is detected in the cloud archive.
+var ErrEndOfWALStreamReached = status.Errorf(codes.OutOfRange, "end of WAL reached")
 
-// ShouldPrintStackTrace tells whether the sidecar log stream should contain the stack trace
-func (e walNotFoundError) ShouldPrintStackTrace() bool {
-	return false
-}
+// ErrMissingPermissions is raised when the sidecar has no
+// permission to download the credentials needed to reach
+// the object storage.
+// This will be fixed by the reconciliation loop in the
+// operator plugin.
+var ErrMissingPermissions = status.Errorf(codes.FailedPrecondition,
+	"no permission to download the backup credentials, retrying")
 
-// Error implements the error interface
-func (e walNotFoundError) Error() string {
-	return "WAL file not found"
+// newWALNotFoundError returns a error that states that a
+// certain WAL file has not been found. This error is
+// compatible with GRPC status codes, resulting in a 404
+// being used as a response code.
+func newWALNotFoundError(walName string) error {
+	return status.Errorf(codes.NotFound, "wal %q not found", walName)
 }

internal/cnpgi/common/wal.go

@@ -27,13 +27,6 @@ import (
 	"github.com/cloudnative-pg/plugin-barman-cloud/internal/cnpgi/operator/config"
 )
 
-// ErrMissingPermissions is raised when the sidecar has no
-// permission to download the credentials needed to reach
-// the object storage.
-// This will be fixed by the reconciliation loop in the
-// operator plugin.
-var ErrMissingPermissions = fmt.Errorf("no permission to download the backup credentials, retrying")
-
 // SpoolManagementError is raised when a spool management
 // error has been detected
 type SpoolManagementError struct {
@@ -95,11 +88,14 @@ func (w WALServiceImplementation) Archive(
 	ctx context.Context,
 	request *wal.WALArchiveRequest,
 ) (*wal.WALArchiveResult, error) {
-	contextLogger := log.FromContext(ctx)
-	contextLogger.Debug("starting wal archive")
-
 	baseWalName := path.Base(request.GetSourceFileName())
 
+	contextLogger := log.FromContext(ctx)
+	contextLogger.Debug("wal archive start", "walName", baseWalName)
+	defer func() {
+		contextLogger.Debug("wal archive end", "walName", baseWalName)
+	}()
+
 	// Step 1: parse the configuration and get the environment variables needed
 	// for barman-cloud-wal-archive
 	configuration, err := config.NewFromClusterJSON(request.ClusterDefinition)
@@ -122,6 +118,7 @@ func (w WALServiceImplementation) Archive(
 	)
 	if err != nil {
 		if apierrors.IsForbidden(err) {
+			contextLogger.Info(ErrMissingPermissions.Error())
 			return nil, ErrMissingPermissions
 		}
 		return nil, err
@@ -350,7 +347,7 @@ func (w WALServiceImplementation) restoreFromBarmanObjectStore(
 	// The failure has already been logged in walRestorer.RestoreList method
 	if walStatus[0].Err != nil {
 		if errors.Is(walStatus[0].Err, barmanRestorer.ErrWALNotFound) {
-			return newWALNotFoundError()
+			return newWALNotFoundError(walStatus[0].WalName)
 		}
 
 		return walStatus[0].Err
@@ -457,9 +454,6 @@ func gatherWALFilesToRestore(walName string, parallel int) (walList []string, er
 	return walList, err
 }
 
-// ErrEndOfWALStreamReached is returned when end of WAL is detected in the cloud archive.
-var ErrEndOfWALStreamReached = errors.New("end of WAL reached")
-
 // checkEndOfWALStreamFlag returns ErrEndOfWALStreamReached if the flag is set in the restorer.
 func checkEndOfWALStreamFlag(walRestorer *barmanRestorer.WALRestorer) error {
 	contain, err := walRestorer.IsEndOfWALStream()