115 lines
3.2 KiB
Go
115 lines
3.2 KiB
Go
// Copyright 2026 Alibaba Group
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package helpers
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import (
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"fmt"
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"io"
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"os"
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"path/filepath"
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)
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type atomicTempFile interface {
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io.Writer
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Name() string
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Chmod(os.FileMode) error
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Sync() error
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Close() error
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}
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var (
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atomicMkdirAll = os.MkdirAll
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atomicCreateTemp = func(dir, pattern string) (atomicTempFile, error) {
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return os.CreateTemp(dir, pattern)
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}
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atomicRemove = os.Remove
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atomicRename = os.Rename
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)
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// AtomicWrite writes data to path atomically by creating a temp file in the
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// same directory, writing and fsyncing the data, then renaming over the target.
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// It replaces os.WriteFile for all config and download file writes.
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//
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// os.WriteFile truncates the target before writing, so a process kill (CI timeout,
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// OOM, Ctrl+C) between truncate and completion leaves the file empty or partial.
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// AtomicWrite avoids this: on any failure the temp file is cleaned up and the
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// original file remains untouched.
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func AtomicWrite(path string, data []byte, perm os.FileMode) error {
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return atomicWrite(path, perm, func(tmp atomicTempFile) error {
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_, err := tmp.Write(data)
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return err
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})
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}
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// AtomicWriteFromReader atomically copies reader contents into path.
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func AtomicWriteFromReader(path string, reader io.Reader, perm os.FileMode) (int64, error) {
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var copied int64
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err := atomicWrite(path, perm, func(tmp atomicTempFile) error {
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n, err := io.Copy(tmp, reader)
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copied = n
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return err
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})
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if err != nil {
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return 0, err
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}
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return copied, nil
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}
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// AtomicWriteJSON is a convenience wrapper for writing JSON data atomically.
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// It uses 0600 permissions by default for sensitive data.
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func AtomicWriteJSON(path string, data []byte) error {
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return AtomicWrite(path, data, 0600)
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}
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func atomicWrite(path string, perm os.FileMode, writeFn func(tmp atomicTempFile) error) error {
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dir := filepath.Dir(path)
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// Ensure directory exists with secure permissions
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if err := atomicMkdirAll(dir, 0700); err != nil {
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return fmt.Errorf("create directory: %w", err)
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}
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tmp, err := atomicCreateTemp(dir, "."+filepath.Base(path)+".*.tmp")
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if err != nil {
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return fmt.Errorf("create temp file: %w", err)
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}
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tmpName := tmp.Name()
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success := false
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defer func() {
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if !success {
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tmp.Close()
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atomicRemove(tmpName)
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}
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}()
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if err := tmp.Chmod(perm); err != nil {
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return fmt.Errorf("set permissions: %w", err)
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}
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if err := writeFn(tmp); err != nil {
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return fmt.Errorf("write data: %w", err)
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}
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if err := tmp.Sync(); err != nil {
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return fmt.Errorf("sync to disk: %w", err)
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}
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if err := tmp.Close(); err != nil {
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return fmt.Errorf("close temp file: %w", err)
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}
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if err := atomicRename(tmpName, path); err != nil {
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return fmt.Errorf("rename to final: %w", err)
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}
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success = true
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return nil
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}
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