如何从pythonanywhere烧瓶WebApp（通过pandas＆amp; sqlalchemy）访问外部MySQL数据库：接收sqlalchemy.exc.exc.operationalerror

Question

我正在尝试将烧瓶WebApp转换为在Pythonanywhere上运行，而不是我当前托管并完美运行的Raspberry Pi。

WebApp的核心功能之一是使用Pandas查询外部托管的MySQL数据库（未托管在Pythonanywhere上）。

以前，我已经使用以下方法进行了此操作，没有任何麻烦：

import pandas as pd
URI=f"mysql://{user}@{host}:{port}/{schema}"
my_dataframe=pd.read_sql_query(sql="select * from users",con=URI)

使用pythonanywhere托管的WebApp进行尝试，导致502-备用错误，错误日志的错误日志：（

File "./webapp.py", line 240, in ages
    message_, success=scripts.ages.main()
  File "./scripts/ages.py", line 22, in main
    my_dataframe=pd.read_sql_query(sql="select * from users",con=URI)
  File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/pandas/io/sql.py", line 383, in read_sql_query
    chunksize=chunksize,
  File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/pandas/io/sql.py", line 1295, in read_query
    result = self.execute(*args)
  File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/pandas/io/sql.py", line 1162, in execute
    *args, **kwargs
  File "<string>", line 2, in execute
  File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/util/deprecations.py", line 401, in warned
    return fn(*args, **kwargs)
  File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 3145, in execute
    connection = self.connect(close_with_result=True)
  File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 3204, in connect
    return self._connection_cls(self, close_with_result=close_with_result)
  File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 96, in __init__
    else engine.raw_connection()
  File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 3283, in raw_connection
    return self._wrap_pool_connect(self.pool.connect, _connection)
  File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 3254, in _wrap_pool_connect
    e, dialect, self
  File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 2101, in _handle_dbapi_exception_noconnection
    sqlalchemy_exception, with_traceback=exc_info[2], from_=e
  File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/util/compat.py", line 207, in raise_
    raise exception
  File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 3250, in _wrap_pool_connect
    return fn()
  File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/pool/base.py", line 310, in connect
    return _ConnectionFairy._checkout(self)
  File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/pool/base.py", line 868, in _checkout
    fairy = _ConnectionRecord.checkout(pool)
  File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/pool/base.py", line 476, in checkout
    rec = pool._do_get()
  File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/pool/impl.py", line 146, in _do_get
    self._dec_overflow()
  File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/util/langhelpers.py", line 72, in __exit__
    with_traceback=exc_tb,
  File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/util/compat.py", line 207, in raise_
    raise exception
  File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/pool/impl.py", line 143, in _do_get
    return self._create_connection()
  File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/pool/base.py", line 256, in _create_connection
    return _ConnectionRecord(self)
  File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/pool/base.py", line 371, in __init__
    self.__connect()
  File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/pool/base.py", line 666, in __connect
    pool.logger.debug("Error on connect(): %s", e)
  File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/util/langhelpers.py", line 72, in __exit__
    with_traceback=exc_tb,
  File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/util/compat.py", line 207, in raise_
    raise exception
  File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/pool/base.py", line 661, in __connect
    self.dbapi_connection = connection = pool._invoke_creator(self)
  File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/engine/create.py", line 590, in connect
    return dialect.connect(*cargs, **cparams)
  File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/engine/default.py", line 597, in connect
    return self.dbapi.connect(*cargs, **cparams)
  File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/MySQLdb/__init__.py", line 130, in Connect
    return Connection(*args, **kwargs)
  File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/MySQLdb/connections.py", line 185, in __init__
    super().__init__(*args, **kwargs2)
sqlalchemy.exc.OperationalError: (MySQLdb._exceptions.OperationalError) (2003, "Can't connect to MySQL server on '34.105.08.12:8080' (111)")
(Background on this error at: https://sqlalche.me/e/14/e3q8)

我更改了IP）

我已经去看了在链接网站 https://sqlalche.me/e/e/14/e3q8 't看到任何有用的东西。

我还尝试过谷歌搜索如何在Pythonanywhere中使用Sqlalchemy。这主要导致有关连接到Pythonanywhere托管的数据库的问题，这对我没有帮助。

我遇到了这个链接：

https://help.pythonanywhere.com/pages/usingsqlalchemywithmysql/

我实际上不知道它是指使用SQLalchemy连接到pythonanywhere托管MySQL数据库或外部数据库，但无论如何我还是尝试实现此功能。我怀疑这会有所作为，但是URI位于PANDAS SQL查询的单独文件中。

#credentials.py
from sqlalchemy import create_engine
URI_string=f"mysql://{user}@{host}:{port}/{schema}"
URI = create_engine(URI_string, pool_recycle=280)

import pandas as pd
import credentials
my_dataframe=pd.read_sql_query(sql="select * from users",con=credentials.URI)

通过此更改在PI上进行测试时，WebApp仍然有效，但是在PyanyWhere进行测试并接收相同的错误日志输出时，结果没有差异。

如果有人有任何想法，请告诉我！

Answer 1

如果您使用的是免费帐户，则只能使用http（s）从pythonanywhere连接到批准的网站列表。因此，外部数据库连接将无法从免费帐户中使用。