Gramex Redis Cache随机抛出TypeError:无法序列化_thread.RLock对象求助

正在使用Gramex Redis Cache服务，偶尔会随机出现错误并在Gramex控制台抛出异常，请求协助解决。

错误日志 #

E 19-Jul 07:23:59 gramex:cache 8000 gramex.cache.open: <class 'gramex.services.rediscache.RedisCache'> cannot cache <tornado.template.Template object at 0x7f5cc43c1290>
Traceback (most recent call last):
  File "/home/star/conda/lib/python3.7/site-packages/tornado/web.py", line 1704, in _execute
    result = await result
  File "/home/star/conda/lib/python3.7/site-packages/tornado/gen.py", line 769, in run
    yielded = self.gen.throw(*exc_info)  # type: ignore
  File "/home/star/conda/lib/python3.7/site-packages/gramex/handlers/filehandler.py", line 188, in get
    yield self._get_path(self.root)
  File "/home/star/conda/lib/python3.7/site-packages/tornado/gen.py", line 762, in run
    value = future.result()
  File "/home/star/conda/lib/python3.7/site-packages/tornado/gen.py", line 234, in wrapper
    yielded = ctx_run(next, result)
  File "/home/star/conda/lib/python3.7/site-packages/gramex/handlers/filehandler.py", line 244, in _get_path
    raise HTTPError(FORBIDDEN, f'{self.file} not allowed')
tornado.web.HTTPError: HTTP 403: Forbidden (/home/star/conda/lib/python3.7/site-packages/gramex/favicon.ico not allowed)
 
During handling of the above exception, another exception occurred:
 
Traceback (most recent call last):
  File "/home/star/conda/lib/python3.7/site-packages/gramex/cache.py", line 168, in open
    _cache[key] = cached
  File "/home/star/conda/lib/python3.7/site-packages/gramex/services/rediscache.py", line 58, in __setitem__
    value = pickle.dumps(value, pickle.HIGHEST_PROTOCOL)
TypeError: can't pickle _thread.RLock objects

gramex.yaml配置 #

cache:
    memory:
      default: false
    redis:
      type: redis
      # path: $REDIS_CACHE_HOST:$REDIS_CACHE_PORT:$REDIS_CACHE_DB
      path: $REDIS_CACHE_HOST:$REDIS_CACHE_PORT:$REDIS_CACHE_DB:password=$REDIS_CACHE_PASSWORD
      size: 0 #GB cache
      default: true


app:
  session:
    type: redis         # Persistent multi-instance data store
    path: $REDIS_HOST:$REDIS_PORT:0:password=$REDIS_PASSWORD     # Redis server
    expiry: 10          # Session cookies expiry in days
    purge: 86400        # Delete old sessions periodically (in seconds)
    domain: .mydomain.com


url:
  show_daypart_data:
    pattern: /$YAMLURL/show_daypart_data
    handler: FormHandler
    kwargs:
      cors: true
      methods: $http_methods
      headers:
        $request_headers
      frm_30:
        url: $BigQ_CONN
        credentials_path: $CREDENTIAL_PATH
        state: my_utilities.cache_query(handler, '30 mi')
        queryfunction: star.get_show_daypart_query(handler, 'frm_period')
      modify: star.modify_show_daypart_data(handler, data)
      default:
        _limit: 450000
      error: *API_ERROR

对应的Python函数（state参数使用） #

def cache_query(handler, table):
    '''Runs a cache validation query'''
    args = handler.argparse(
        src={'default': 'any'},
        view={'default': 'net'})
    state = ''
    for tbl in table.split('+'):
        table_name = rds_tables[args.src][tbl]
        query = f"""SELECT CONCAT(year, '-', week) as week FROM {table_name}
                        ORDER BY year DESC, week DESC limit 1"""
        try:
            val = REDIS_CACHE[str(query)]
            if not val:
                df = gramex.cache.query(query, db_engine)
                val = df.week.iloc[0]
                REDIS_CACHE[str(query)] = val
            state = '-' + val
        except Exception as error:
            app_log.error(f'Cache query failed ==> {error}')
            pass
    return state

解决方案 #

1. 修复favicon.ico的403错误 #

错误根源是Gramex尝试访问/home/star/conda/lib/python3.7/site-packages/gramex/favicon.ico时被禁止，触发HTTP 403异常。可通过以下方式解决：

• 在gramex.yaml的url部分添加允许访问favicon.ico的规则：

  url:
    favicon:
      pattern: /favicon.ico
      handler: FileHandler
      kwargs:
        path: /path/to/your/favicon.ico  # 指定项目内合法的favicon路径，如项目根目录下的文件
        headers:
          Cache-Control: public, max-age=86400
  

• 或调整FileHandler权限配置，允许访问Gramex包内的favicon.ico（不推荐，建议使用自定义favicon）。

2. 解决Redis缓存无法序列化的问题 #

处理403异常时，Gramex尝试缓存tornado.template.Template对象，该对象包含无法被pickle序列化的_thread.RLock锁对象，导致报错。可通过以下方式处理：

• 排除特定路径的缓存：在cache配置中，为favicon.ico这类静态资源路径禁用Redis缓存，改用内存缓存：

  cache:
    memory:
      default: false
      paths:
        /favicon.ico: true  # 对favicon.ico使用内存缓存，避免Redis序列化问题
    redis:
      type: redis
      path: $REDIS_CACHE_HOST:$REDIS_CACHE_PORT:$REDIS_CACHE_DB:password=$REDIS_CACHE_PASSWORD
      size: 0
      default: true
  

• 检查缓存内容：确保所有手动缓存的内容都是可序列化类型（当前cache_query函数缓存的是字符串，这部分无问题，问题出在Gramex内部异常处理时的缓存操作）。

内容的提问来源于stack exchange，提问作者Nivedita Deshmukh