多執行緒中的共享物件
課程
這段程式碼出現了非持續的 bug，表現不一致。其隨機性使得它難以重現和有效地除錯。
這種非持續行為源自於 translate_markdown_file 函數，特別是 translate_front_matter 函數，處理共享數據的方式。這些函數可能會同時訪問和修改共享數據結構，如字典或列表，而沒有正確的同步。
當多個線程同時訪問和修改相同的數據時，會導致競爭條件。競爭條件發生在數據的最終狀態依賴於線程執行的不可預測順序。這可能導致數據損壞、意料之外的程式行為以及你所觀察到的非持續 bug。
要解決這個問題，你應該要或避免在線程之間共享可變數據，或使用適當的同步機制，如鎖，來保護共享數據。在這個情況下，front_matter_dict 被修改成為不安全的，解決方案是在修改之前創建一個副本。這在程式碼中已經完成，但需要理解為什麼這是必要的。
背景
with concurrent.futures.ThreadPoolExecutor(max_workers=MAX_THREADS) as executor:
futures = []
for filename in changed_files:
input_file = filename
for lang in languages:
print(f"Submitting translation job for {filename} to {lang}...")
future = executor.submit(translate_markdown_file, input_file, os.path.join(f"_posts/{lang}", os.path.basename(filename).replace(".md", f"-{lang}.md")), lang, dry_run)
futures.append(future)
for future in concurrent.futures.as_completed(futures):
try:
future.result()
except Exception as e:
print(f"A thread failed: {e}")
修改前
def translate_front_matter(front_matter, target_language, input_file):
print(f" Translating front matter for: {input_file}")
if not front_matter:
print(f" No front matter found for: {input_file}")
return ""
try:
front_matter_dict = {}
if front_matter:
front_matter_dict = yaml.safe_load(front_matter)
print(f" Front matter after safe_load: {front_matter_dict}")
if 'title' in front_matter_dict:
print(f" Translating title: {front_matter_dict['title']}")
if not (input_file == 'original/2025-01-11-resume-en.md' and target_language in ['zh', 'fr']):
if isinstance(front_matter_dict['title'], str):
translated_title = translate_text(front_matter_dict['title'], target_language)
if translated_title:
translated_title = translated_title.strip()
if len(translated_title) > 300:
translated_title = translated_title.split('\n')[0]
front_matter_dict['title'] = translated_title
print(f" Translated title to: {translated_title}")
else:
print(f" Title translation failed for: {input_file}")
else:
print(f" Title is not a string, skipping translation for: {input_file}")
else:
print(f" Skipping title translation for {input_file} to {target_language}")
# Always set lang to target_language
# Determine if the file is a translation
original_lang = 'en' # Default to english
if 'lang' in front_matter_dict:
original_lang = front_matter_dict['lang']
if target_language != original_lang:
front_matter_dict['lang'] = target_language
front_matter_dict['translated'] = True
print(f" Marked as translated to {target_language} for: {input_file}")
else:
front_matter_dict['translated'] = False
print(f" Not marked as translated for: {input_file}")
result = "---\n" + yaml.dump(front_matter_dict, allow_unicode=True) + "---"
print(f" Front matter translation complete for: {input_file}")
return result
except yaml.YAMLError as e:
print(f" Error parsing front matter: {e}")
return front_matter
修改後
def translate_front_matter(front_matter, target_language, input_file):
print(f" Translating front matter for: {input_file}")
if not front_matter:
print(f" No front matter found for: {input_file}")
return ""
try:
front_matter_dict = {}
if front_matter:
front_matter_dict = yaml.safe_load(front_matter)
print(f" Front matter after safe_load: {front_matter_dict}")
front_matter_dict_copy = front_matter_dict.copy()
if 'title' in front_matter_dict_copy:
print(f" Translating title: {front_matter_dict_copy['title']}")
if not (input_file == 'original/2025-01-11-resume-en.md' and target_language in ['zh', 'fr']):
if isinstance(front_matter_dict_copy['title'], str):
translated_title = translate_text(front_matter_dict_copy['title'], target_language)
if translated_title:
translated_title = translated_title.strip()
if len(translated_title) > 300:
translated_title = translated_title.split('\n')[0]
front_matter_dict_copy['title'] = translated_title
print(f" Translated title to: {translated_title}")
else:
print(f" Title translation failed for: {input_file}")
else:
print(f" Title is not a string, skipping translation for: {input_file}")
else:
print(f" Skipping title translation for {input_file} to {target_language}")
# Always set lang to target_language
front_matter_dict_copy['lang'] = target_language
front_matter_dict_copy['translated'] = True
result = "---\n" + yaml.dump(front_matter_dict_copy, allow_unicode=True) + "---"
print(f" Front matter translation complete for: {input_file}")
return result
except yaml.YAMLError as e:
print(f" Error parsing front matter: {e}")
return front_matter