Handle scenario where agent tries to delete a file that does not exist during a config apply

internal/file/file_manager_service.go

@@ -73,14 +73,19 @@ type (
 
 	fileManagerServiceInterface interface {
 		UpdateOverview(ctx context.Context, instanceID string, filesToUpdate []*mpi.File, iteration int) error
-		ConfigApply(ctx context.Context, configApplyRequest *mpi.ConfigApplyRequest) (writeStatus model.WriteStatus,
-			err error)
+		ConfigApply(
+			ctx context.Context,
+			configApplyRequest *mpi.ConfigApplyRequest,
+		) (writeStatus model.WriteStatus, err error)
 		Rollback(ctx context.Context, instanceID string) error
 		UpdateFile(ctx context.Context, instanceID string, fileToUpdate *mpi.File) error
 		ClearCache()
 		UpdateCurrentFilesOnDisk(ctx context.Context, updateFiles map[string]*mpi.File, referenced bool) error
-		DetermineFileActions(currentFiles map[string]*mpi.File, modifiedFiles map[string]*model.FileCache) (
-			map[string]*model.FileCache, map[string][]byte, error)
+		DetermineFileActions(
+			ctx context.Context,
+			currentFiles map[string]*mpi.File,
+			modifiedFiles map[string]*model.FileCache,
+		) (map[string]*model.FileCache, map[string][]byte, error)
 		IsConnected() bool
 		SetIsConnected(isConnected bool)
 	}
@@ -510,8 +515,11 @@ func (fms *FileManagerService) ConfigApply(ctx context.Context,
 		return model.Error, allowedErr
 	}
 
-	diffFiles, fileContent, compareErr := fms.DetermineFileActions(fms.currentFilesOnDisk,
-		ConvertToMapOfFileCache(fileOverview.GetFiles()))
+	diffFiles, fileContent, compareErr := fms.DetermineFileActions(
+		ctx,
+		fms.currentFilesOnDisk,
+		ConvertToMapOfFileCache(fileOverview.GetFiles()),
+	)
 
 	if compareErr != nil {
 		return model.Error, compareErr
@@ -546,7 +554,7 @@ func (fms *FileManagerService) ClearCache() {
 
 // nolint:revive,cyclop
 func (fms *FileManagerService) Rollback(ctx context.Context, instanceID string) error {
-	slog.InfoContext(ctx, "Rolling back config for instance", "instanceid", instanceID)
+	slog.InfoContext(ctx, "Rolling back config for instance", "instance_id", instanceID)
 
 	fms.filesMutex.Lock()
 	defer fms.filesMutex.Unlock()
@@ -714,6 +722,7 @@ func (fms *FileManagerService) checkAllowedDirectory(checkFiles []*mpi.File) err
 // that have changed and a map of the contents for each updated and deleted file. Key to both maps is file path
 // nolint: revive,cyclop,gocognit
 func (fms *FileManagerService) DetermineFileActions(
+	ctx context.Context,
 	currentFiles map[string]*mpi.File,
 	modifiedFiles map[string]*model.FileCache,
 ) (
@@ -736,6 +745,7 @@ func (fms *FileManagerService) DetermineFileActions(
 			return nil, nil, manifestFileErr
 		}
 	}
+
 	// if file is in manifestFiles but not in modified files, file has been deleted
 	// copy contents, set file action
 	for fileName, manifestFile := range filesMap {
@@ -745,7 +755,12 @@ func (fms *FileManagerService) DetermineFileActions(
 			// Read file contents before marking it deleted
 			fileContent, readErr := os.ReadFile(fileName)
 			if readErr != nil {
-				return nil, nil, fmt.Errorf("error reading file %s: %w", fileName, readErr)
+				if errors.Is(readErr, os.ErrNotExist) {
+					slog.DebugContext(ctx, "Unable to backup file contents since file does not exist", "file", fileName)
+					continue
+				} else {
+					return nil, nil, fmt.Errorf("error reading file %s: %w", fileName, readErr)
+				}
 			}
 			fileContents[fileName] = fileContent
 

internal/file/file_manager_service_test.go

@@ -548,6 +548,7 @@ func TestFileManagerService_Rollback(t *testing.T) {
 }
 
 func TestFileManagerService_DetermineFileActions(t *testing.T) {
+	ctx := context.Background()
 	tempDir := os.TempDir()
 
 	deleteTestFile := helpers.CreateFileWithErrorCheck(t, tempDir, "nginx_delete.conf")
@@ -573,7 +574,6 @@ func TestFileManagerService_DetermineFileActions(t *testing.T) {
 
 	addTestFile := helpers.CreateFileWithErrorCheck(t, tempDir, "nginx_add.conf")
 	defer helpers.RemoveFileWithErrorCheck(t, addTestFile.Name())
-	t.Logf("Adding file: %s", addTestFile.Name())
 	addFileContent := []byte("test add file")
 	addErr := os.WriteFile(addTestFile.Name(), addFileContent, 0o600)
 	require.NoError(t, addErr)
@@ -683,6 +683,18 @@ func TestFileManagerService_DetermineFileActions(t *testing.T) {
 			expectedContent: make(map[string][]byte),
 			expectedError:   nil,
 		},
+		{
+			name:          "Test 3: File being deleted already doesn't exist",
+			modifiedFiles: make(map[string]*model.FileCache),
+			currentFiles: map[string]*mpi.File{
+				"/unknown/file.conf": {
+					FileMeta: protos.FileMeta("/unknown/file.conf", files.GenerateHash(fileContent)),
+				},
+			},
+			expectedCache:   make(map[string]*model.FileCache),
+			expectedContent: make(map[string][]byte),
+			expectedError:   nil,
+		},
 	}
 
 	for _, test := range tests {
@@ -697,8 +709,11 @@ func TestFileManagerService_DetermineFileActions(t *testing.T) {
 			fileManagerService := NewFileManagerService(fakeFileServiceClient, types.AgentConfig())
 			require.NoError(tt, err)
 
-			diff, contents, fileActionErr := fileManagerService.DetermineFileActions(test.currentFiles,
-				test.modifiedFiles)
+			diff, contents, fileActionErr := fileManagerService.DetermineFileActions(
+				ctx,
+				test.currentFiles,
+				test.modifiedFiles,
+			)
 			require.NoError(tt, fileActionErr)
 			assert.Equal(tt, test.expectedContent, contents)
 			assert.Equal(tt, test.expectedCache, diff)