external: improve S3 error message (pingcap#59327)

close pingcap#59326

Author: lance6716

br/pkg/storage/ks3.go

@@ -512,8 +512,14 @@ func (rs *KS3Storage) open(
 	}
 
 	if startOffset != r.Start || (endOffset != 0 && endOffset != r.End+1) {
-		return nil, r, errors.Annotatef(berrors.ErrStorageUnknown, "open file '%s' failed, expected range: %s, got: %v",
-			path, *rangeOffset, result.ContentRange)
+		rangeStr := "<empty>"
+		if result.ContentRange != nil {
+			rangeStr = *result.ContentRange
+		}
+		return nil, r, errors.Annotatef(
+			berrors.ErrStorageUnknown,
+			"open file '%s' failed, expected range: %s, got: %s",
+			path, *rangeOffset, rangeStr)
 	}
 
 	return result.Body, r, nil

br/pkg/storage/s3.go

@@ -875,8 +875,13 @@ func (rs *S3Storage) open(
 	}
 
 	if startOffset != r.Start || (endOffset != 0 && endOffset != r.End+1) {
-		return nil, r, errors.Annotatef(berrors.ErrStorageUnknown, "open file '%s' failed, expected range: %s, got: %v",
-			path, *rangeOffset, result.ContentRange)
+		rangeStr := "<empty>"
+		if result.ContentRange != nil {
+			rangeStr = *result.ContentRange
+		}
+		return nil, r, errors.Annotatef(berrors.ErrStorageUnknown,
+			"open file '%s' failed, expected range: %s, got: %s",
+			path, *rangeOffset, rangeStr)
 	}
 
 	return result.Body, r, nil

br/pkg/storage/s3_test.go

@@ -1472,3 +1472,30 @@ func TestS3ReadFileRetryable(t *testing.T) {
 	require.Error(t, err)
 	require.True(t, strings.Contains(err.Error(), errMsg))
 }
+
+func TestOpenRangeMismatchErrorMsg(t *testing.T) {
+	s := createS3Suite(t)
+	ctx := aws.BackgroundContext()
+	start, end := int64(10), int64(30)
+
+	s.s3.EXPECT().
+		GetObjectWithContext(ctx, gomock.Any()).
+		DoAndReturn(func(context.Context, *s3.GetObjectInput, ...request.Option) (*s3.GetObjectOutput, error) {
+			return &s3.GetObjectOutput{
+				ContentRange: aws.String("bytes 10-20/20"),
+			}, nil
+		})
+	reader, err := s.storage.Open(ctx, "test", &ReaderOption{StartOffset: &start, EndOffset: &end})
+	require.ErrorContains(t, err, "expected range: bytes=10-29, got: bytes 10-20/20")
+	require.Nil(t, reader)
+
+	s.s3.EXPECT().
+		GetObjectWithContext(ctx, gomock.Any()).
+		DoAndReturn(func(context.Context, *s3.GetObjectInput, ...request.Option) (*s3.GetObjectOutput, error) {
+			return &s3.GetObjectOutput{}, nil
+		})
+	reader, err = s.storage.Open(ctx, "test", &ReaderOption{StartOffset: &start, EndOffset: &end})
+	// other function will throw error
+	require.ErrorContains(t, err, "ContentRange is empty")
+	require.Nil(t, reader)
+}