我在运行Web服务器/调度程序的EC2上有一个气流实例。我想将MySQL RDS实例连接为后端元数据数据库，而不是本机SQLite。我替换了通过sql_alchemy连接到数据库的Airflow.cfg中的一行，以使用pymysql驱动程序连接到RDS：
#sql_alchemy_conn = sqlite:////home/cloud-user/airflow/airflow.db
sql_alchemy_conn = mysql+pymysql://admin:<PASSWORD>@airflow-db.xxxxxxxxxxxx.us-east-1.rds.amazonaws.com:3306/airflow
连接似乎工作正常，我能够通过在我的EC2实例上设置的MySQL客户端进入RDS实例并查询表。
当我打开或关闭DAG时，在我的shell中得到了这个讨厌的python堆栈跟踪：
[2019-09-30 14:00:51,774] {app.py:1891} ERROR - Exception on /admin/airflow/paused [POST]
Traceback (most recent call last):
File "/home/cloud-user/.local/lib/python2.7/site-packages/flask/app.py", line 2446, in wsgi_app
response = self.full_dispatch_request()
File "/home/cloud-user/.local/lib/python2.7/site-packages/flask/app.py", line 1951, in full_dispatch_request
rv = self.handle_user_exception(e)
File "/home/cloud-user/.local/lib/python2.7/site-packages/flask/app.py", line 1820, in handle_user_exception
reraise(exc_type, exc_value, tb)
File "/home/cloud-user/.local/lib/python2.7/site-packages/flask/app.py", line 1949, in full_dispatch_request
rv = self.dispatch_request()
File "/home/cloud-user/.local/lib/python2.7/site-packages/flask/app.py", line 1935, in dispatch_request
return self.view_functions[rule.endpoint](**req.view_args)
File "/home/cloud-user/.local/lib/python2.7/site-packages/flask_admin/base.py", line 69, in inner
return self._run_view(f, *args, **kwargs)
File "/home/cloud-user/.local/lib/python2.7/site-packages/flask_admin/base.py", line 368, in _run_view
return fn(self, *args, **kwargs)
File "/home/cloud-user/.local/lib/python2.7/site-packages/flask_login/utils.py", line 258, in decorated_view
return func(*args, **kwargs)
File "/home/cloud-user/.local/lib/python2.7/site-packages/airflow/www/utils.py", line 279, in wrapper
session.commit()
File "/home/cloud-user/.local/lib/python2.7/site-packages/sqlalchemy/orm/session.py", line 1027, in commit
self.transaction.commit()
File "/home/cloud-user/.local/lib/python2.7/site-packages/sqlalchemy/orm/session.py", line 494, in commit
self._prepare_impl()
File "/home/cloud-user/.local/lib/python2.7/site-packages/sqlalchemy/orm/session.py", line 473, in _prepare_impl
self.session.flush()
File "/home/cloud-user/.local/lib/python2.7/site-packages/sqlalchemy/orm/session.py", line 2459, in flush
self._flush(objects)
File "/home/cloud-user/.local/lib/python2.7/site-packages/sqlalchemy/orm/session.py", line 2597, in _flush
transaction.rollback(_capture_exception=True)
File "/home/cloud-user/.local/lib/python2.7/site-packages/sqlalchemy/util/langhelpers.py", line 68, in __exit__
compat.reraise(exc_type, exc_value, exc_tb)
File "/home/cloud-user/.local/lib/python2.7/site-packages/sqlalchemy/orm/session.py", line 2557, in _flush
flush_context.execute()
File "/home/cloud-user/.local/lib/python2.7/site-packages/sqlalchemy/orm/unitofwork.py", line 422, in execute
rec.execute(self)
File "/home/cloud-user/.local/lib/python2.7/site-packages/sqlalchemy/orm/unitofwork.py", line 589, in execute
uow,
File "/home/cloud-user/.local/lib/python2.7/site-packages/sqlalchemy/orm/persistence.py", line 245, in save_obj
insert,
File "/home/cloud-user/.local/lib/python2.7/site-packages/sqlalchemy/orm/persistence.py", line 1138, in _emit_insert_statements
statement, params
File "/home/cloud-user/.local/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 988, in execute
return meth(self, multiparams, params)
File "/home/cloud-user/.local/lib/python2.7/site-packages/sqlalchemy/sql/elements.py", line 287, in _execute_on_connection
return connection._execute_clauseelement(self, multiparams, params)
File "/home/cloud-user/.local/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 1107, in _execute_clauseelement
distilled_params,
File "/home/cloud-user/.local/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 1253, in _execute_context
e, statement, parameters, cursor, context
File "/home/cloud-user/.local/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 1473, in _handle_dbapi_exception
util.raise_from_cause(sqlalchemy_exception, exc_info)
File "/home/cloud-user/.local/lib/python2.7/site-packages/sqlalchemy/util/compat.py", line 398, in raise_from_cause
reraise(type(exception), exception, tb=exc_tb, cause=cause)
File "/home/cloud-user/.local/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 1249, in _execute_context
cursor, statement, parameters, context
File "/home/cloud-user/.local/lib/python2.7/site-packages/sqlalchemy/engine/default.py", line 552, in do_execute
cursor.execute(statement, parameters)
File "/home/cloud-user/.local/lib/python2.7/site-packages/pymysql/cursors.py", line 170, in execute
result = self._query(query)
File "/home/cloud-user/.local/lib/python2.7/site-packages/pymysql/cursors.py", line 328, in _query
conn.query(q)
File "/home/cloud-user/.local/lib/python2.7/site-packages/pymysql/connections.py", line 517, in query
self._affected_rows = self._read_query_result(unbuffered=unbuffered)
File "/home/cloud-user/.local/lib/python2.7/site-packages/pymysql/connections.py", line 732, in _read_query_result
result.read()
File "/home/cloud-user/.local/lib/python2.7/site-packages/pymysql/connections.py", line 1075, in read
first_packet = self.connection._read_packet()
File "/home/cloud-user/.local/lib/python2.7/site-packages/pymysql/connections.py", line 684, in _read_packet
packet.check_error()
File "/home/cloud-user/.local/lib/python2.7/site-packages/pymysql/protocol.py", line 220, in check_error
err.raise_mysql_exception(self._data)
File "/home/cloud-user/.local/lib/python2.7/site-packages/pymysql/err.py", line 109, in raise_mysql_exception
raise errorclass(errno, errval)
ProgrammingError: (pymysql.err.ProgrammingError) (1064, u"You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '[(\\'is_paused\\', u\\'true\\'), (\\'dag_id\\', u\\'test\\')]'')' at line 1")
[SQL: INSERT INTO log (dttm, dag_id, task_id, event, execution_date, owner, extra) VALUES (%(dttm)s, %(dag_id)s, %(task_id)s, %(event)s, %(execution_date)s, %(owner)s, %(extra)s)]
[parameters: {'task_id': None, 'extra': "[('is_paused', u'true'), ('dag_id', u'test')]", 'execution_date': None, 'event': 'paused', 'owner': 'anonymous', 'dttm': datetime.datetime(2019, 9, 30, 18, 0, 51, 768073, tzinfo=<Timezone [UTC]>), 'dag_id': u'test'}]
(Background on this error at: http://sqlalche.me/e/f405)
根据我在Airflow文档上看到的内容，我正在正确进行更改，并且'airflow initdb / resetdb'命令执行没有错误。
我已经花了很多时间来搜索该错误，但是对于该问题没有明确的答案。我真的不确定是否缺少先决条件，还是应该使用其他连接器？
EDIT：我正在使用python 2.7，如堆栈跟踪所示。 Airflow声称在短期内具有兼容性，但是我看到升级到python 3.6之后[Link to other solution]，另一个SO用户的问题消失了。如果可以使用，我会尝试并进行更新。
看来解决方案的确是利用虚拟环境升级到python 3.6，这是由于python 2.x和3.y具有Linux系统和Airflow所要求的双重性。具体来说，我遵循此guide，而我的DAG似乎已成功执行。