use hardlinks for plugin cache copy to save resources

integration_test/module_controller_with_runner_test.go

@@ -63,7 +63,7 @@ var _ = Describe("Module controller with Runner", func() {
 			var dst string
 			testRepos.EXPECT().Clone(gomock.Any(), "https://host.xy/dummy/repo.git", gomock.AssignableToTypeOf(dst), "HEAD", "", true).
 				DoAndReturn(func(ctx context.Context, remote, dst, branch, pathspec string, rmGitDir bool) (string, error) {
-					return "commit124", sysutil.CopyDir(context.TODO(), filepath.Join("src", "modules"), dst, true)
+					return "commit124", sysutil.CopyDirWithHardLinks(context.TODO(), filepath.Join("src", "modules"), dst)
 				}).AnyTimes()
 
 			testMetrics.EXPECT().UpdateModuleRunDuration(gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any()).AnyTimes()

runner/plugin.go

@@ -74,7 +74,7 @@ func (pcp *pluginCache) new() string {
 	pcp.RLock()
 	defer pcp.RUnlock()
 
-	if err := sysutil.CopyDir(ctx, pcp.main, tmpPC, true); err != nil {
+	if err := sysutil.CopyDirWithHardLinks(ctx, pcp.main, tmpPC); err != nil {
 		pcp.log.Error("unable to create copy providers to plugin cache dir", "err", err)
 		sysutil.RemoveAll(tmpPC)
 		return ""
@@ -94,7 +94,7 @@ func (pcp *pluginCache) done(tmpPC string) {
 	pcp.Lock()
 	defer pcp.Unlock()
 
-	if err := sysutil.CopyDir(ctx, tmpPC, pcp.main, false); err != nil {
+	if err := sysutil.CopyDirWithHardLinks(ctx, tmpPC, pcp.main); err != nil {
 		pcp.log.Error("unable to create copy tmp to main dir", "err", err)
 	}
 }

sysutil/filesystem.go

@@ -20,31 +20,29 @@ func RemoveAll(dir string) error {
 	return cmd.Run()
 }
 
-// CopyFile copies a file
-func CopyFile(src, dst string, withReplace bool) error {
+// HardLinkFile creates hard link if dst doesn't exits
+func HardLinkFile(src, dst string) error {
 	var err error
 	var srcInfo os.FileInfo
 
 	if srcInfo, err = os.Stat(src); err != nil {
 		return err
 	}
 
-	if !withReplace {
-		// skip if dst file already exits
-		if dstInfo, err := os.Stat(dst); err == nil {
-			if srcInfo.Name() == dstInfo.Name() &&
-				srcInfo.Size() == dstInfo.Size() {
-				return nil
-			}
+	// skip if dst file already exits
+	if dstInfo, err := os.Stat(dst); err == nil {
+		if srcInfo.Name() == dstInfo.Name() {
+			return nil
 		}
 	}
 
-	// create hard link to save cpu/mem/disk io
+	// once plugin binary is downloaded it will not be modified hence
+	// we can use hard link instead of copy to save resources and time.
 	return os.Link(src, dst)
 }
 
-// CopyDir copies a dir recursively
-func CopyDir(ctx context.Context, src string, dst string, withReplace bool) error {
+// CopyDirWithHardLinks creates hard links of files from src recursively at dst
+func CopyDirWithHardLinks(ctx context.Context, src string, dst string) error {
 	var err error
 	var fileDescriptors []os.DirEntry
 	var srcInfo os.FileInfo
@@ -66,17 +64,12 @@ func CopyDir(ctx context.Context, src string, dst string, withReplace bool) erro
 		dstPath := path.Join(dst, fd.Name())
 
 		if fd.IsDir() {
-			if err := CopyDir(ctx, srcPath, dstPath, withReplace); err != nil {
+			if err := CopyDirWithHardLinks(ctx, srcPath, dstPath); err != nil {
 				return err
 			}
 		} else {
-			select {
-			case <-ctx.Done():
-				return ctx.Err()
-			default:
-				if err := CopyFile(srcPath, dstPath, withReplace); err != nil {
-					return err
-				}
+			if err := HardLinkFile(srcPath, dstPath); err != nil {
+				return err
 			}
 		}
 	}

sysutil/filesystem_test.go

@@ -48,7 +48,7 @@ func TestCopyDirWithReplace(t *testing.T) {
 	}
 
 	// Copy the directory.
-	err := CopyDir(context.TODO(), srcDir, dstDir, true)
+	err := CopyDirWithHardLinks(context.TODO(), srcDir, dstDir)
 	if err != nil {
 		t.Fatalf("error copying directory: %v", err)
 	}
@@ -123,7 +123,7 @@ func TestCopyDirWithoutReplace(t *testing.T) {
 	}
 
 	// Copy the directory.
-	err := CopyDir(context.TODO(), srcDir, dstDir, false)
+	err := CopyDirWithHardLinks(context.TODO(), srcDir, dstDir)
 	if err != nil {
 		t.Fatalf("error copying directory: %v", err)
 	}