Question

当芹菜试图清理后端时，我面临以下异常。

最有可能的是，这是由于MySQL disconnect issue而发生的，可以通过使用pool_recycle参数并稍后重试该任务来解决。但这不在我的手中 - 我猜芹菜需要为此提供支持吗？

现在我的问题是，什么是后端清理任务以及这样一个失败的任务如何影响我们的系统？

日志：

[2014-04-08 04:00:00,017: INFO/Beat] Scheduler: Sending due task celery.backend_cleanup (celery.backend_cleanup)
[2014-04-08 04:00:00,020: INFO/MainProcess] Received task: celery.backend_cleanup[b70acd50-e72d-43b1-a702-0bfa8e7e83a6] expires:[2014-04-08 16:00:00.018317+01:00]
[2014-04-08 04:00:00,036: ERROR/MainProcess] Task celery.backend_cleanup[b70acd50-e72d-43b1-a702-0bfa8e7e83a6] raised unexpected: OperationalError('(OperationalError) MySQL Connection not available.',)
Traceback (most recent call last):
  File "/webapps/phoenix/lib/python3.3/site-packages/celery/app/trace.py", line 238, in trace_task
    R = retval = fun(*args, **kwargs)
  File "/webapps/phoenix/lib/python3.3/site-packages/celery/app/trace.py", line 416, in __protected_call__
    return self.run(*args, **kwargs)
  File "/webapps/phoenix/lib/python3.3/site-packages/celery/app/builtins.py", line 56, in backend_cleanup
    app.backend.cleanup()
  File "/webapps/phoenix/lib/python3.3/site-packages/celery/backends/database/__init__.py", line 180, in cleanup
    Task.date_done < (now - expires)).delete()
  File "/webapps/phoenix/lib/python3.3/site-packages/sqlalchemy/orm/query.py", line 2626, in delete
    delete_op.exec_()
  File "/webapps/phoenix/lib/python3.3/site-packages/sqlalchemy/orm/persistence.py", line 866, in exec_
    self._do_exec()
  File "/webapps/phoenix/lib/python3.3/site-packages/sqlalchemy/orm/persistence.py", line 991, in _do_exec
    params=self.query._params)
  File "/webapps/phoenix/lib/python3.3/site-packages/sqlalchemy/orm/session.py", line 978, in execute
    clause, params or {})
  File "/webapps/phoenix/lib/python3.3/site-packages/sqlalchemy/engine/base.py", line 664, in execute
    return meth(self, multiparams, params)
  File "/webapps/phoenix/lib/python3.3/site-packages/sqlalchemy/sql/elements.py", line 282, in _execute_on_connection
    return connection._execute_clauseelement(self, multiparams, params)
  File "/webapps/phoenix/lib/python3.3/site-packages/sqlalchemy/engine/base.py", line 761, in _execute_clauseelement
    compiled_sql, distilled_params
  File "/webapps/phoenix/lib/python3.3/site-packages/sqlalchemy/engine/base.py", line 828, in _execute_context
    None, None)
  File "/webapps/phoenix/lib/python3.3/site-packages/sqlalchemy/engine/base.py", line 1023, in _handle_dbapi_exception
    exc_info
  File "/webapps/phoenix/lib/python3.3/site-packages/sqlalchemy/util/compat.py", line 174, in raise_from_cause
    reraise(type(exception), exception, tb=exc_tb, cause=exc_value)
  File "/webapps/phoenix/lib/python3.3/site-packages/sqlalchemy/util/compat.py", line 167, in reraise
    raise value.with_traceback(tb)
  File "/webapps/phoenix/lib/python3.3/site-packages/sqlalchemy/engine/base.py", line 824, in _execute_context
    context = constructor(dialect, self, conn, *args)
  File "/webapps/phoenix/lib/python3.3/site-packages/sqlalchemy/engine/default.py", line 507, in _init_compiled
    self.cursor = self.create_cursor()
  File "/webapps/phoenix/lib/python3.3/site-packages/sqlalchemy/engine/default.py", line 671, in create_cursor
    return self._dbapi_connection.cursor()
  File "/webapps/phoenix/lib/python3.3/site-packages/sqlalchemy/pool.py", line 548, in cursor
    return self.connection.cursor(*args, **kwargs)
  File "/webapps/phoenix/lib/python3.3/site-packages/mysql/connector/connection.py", line 1231, in cursor
    raise errors.OperationalError("MySQL Connection not available.")
sqlalchemy.exc.OperationalError: (OperationalError) MySQL Connection not available. 'DELETE FROM celery_taskmeta WHERE celery_taskmeta.date_done < %(date_done_1)s' [{}]

PS我已经检查了这个问题，但似乎是由于一个不同的例外：Celery log shows cleanup failed

Answer 1

最近的芹菜必须重试short lived sessions。

任务是清除未读取的任务结果。如果它失败了，你可能会看到这些结果开始积累，但是否则应该没问题。

你说得对，关于它的文档非常少！

使用SQLAlchemy＆amp; amp; Celery后端清理失败MySQL的

1 个答案: