在Python 3迁移之后，当前没有上下文错误，我应该包括更多的逻辑吗？

问题描述

我正在将Google App Engine Python 2项目转换为Python 3

通过阅读文档，我的理解是我理解的首选路径是直接运行主python程序，就像过去一样跳过dev_appserver.py。

https://cloud.google.com/appengine/docs/standard/python3/tools/local-devserver-command

python3 main.py

--- main.py -- 
# coding: utf-8

import flask
from flask import request,redirect,url_for
from flask_basicauth import BasicAuth

#from urllib# import urlparse,urlunparse

import config


--- config.py

import model
...
33: CONFIG_DB = model.Config.get_master_db()


--- model/config.py
from __future__ import absolute_import

from google.cloud import ndb
#from oauth2client.contrib.appengine import CredentialsNDBProperty

from api import fields
import config
import model
import util
...

class Config(model.Base,model.ConfigAuth):
...
@classmethod
def get_master_db(cls):
57:  return cls.get_or_insert('master')

运行以下跟踪时会产生

Traceback (most recent call last):
  File "main.py",line 9,in <module>
    import config
  File "/home/ffej/cloudpayback/main/config.py",line 33,in <module>
    CONFIG_DB = model.Config.get_master_db()
  File "/home/ffej/cloudpayback/main/model/config.py",line 57,in get_master_db
    return cls.get_or_insert('master')
  File "/home/ffej/cloudpayback/env/lib/python3.8/site-packages/google/cloud/ndb/_options.py",line 89,in wrapper
    return wrapped(*pass_args,**kwargs)
  File "/home/ffej/cloudpayback/env/lib/python3.8/site-packages/google/cloud/ndb/utils.py",line 146,in positional_wrapper
    return wrapped(*args,**kwds)
  File "/home/ffej/cloudpayback/env/lib/python3.8/site-packages/google/cloud/ndb/model.py",line 5698,in _get_or_insert
    return cls._get_or_insert_async(
  File "/home/ffej/cloudpayback/env/lib/python3.8/site-packages/google/cloud/ndb/_options.py",line 5811,in _get_or_insert_async
    key = key_module.Key(cls._get_kind(),name,parent=parent,**key_args)
  File "/home/ffej/cloudpayback/env/lib/python3.8/site-packages/google/cloud/ndb/key.py",line 290,in __new__
    context = context_module.get_context()
  File "/home/ffej/cloudpayback/env/lib/python3.8/site-packages/google/cloud/ndb/context.py",line 96,in get_context
    raise exceptions.ContextError()
google.cloud.ndb.exceptions.ContextError: No current context. NDB calls must be made in context established by google.cloud.ndb.Client.context.

迁移之后是否应该包含其他逻辑来启动/初始化数据存储？

谢谢， 杰夫

解决方法

Python3中NDB库的API发生了重大变化。要在localhost上进行开发，您必须：

• 运行DataStore Emulator，因为您不再运行dev_appserver：

  $ gcloud beta emulators datastore start

• 如果使用the new NDB Library，则每个NDB操作都需要包装在上下文管理器中：

with ndb_client.context(): # <- you need this line
    cls.get_or_insert('master')

编辑：您可以使用中间件，而不是使用上下文管理器包装每个NDB调用，而是将整个请求周期包装到NDB上下文中：

class NDBMiddleware:
    def __init__(self,app):
        self.app = app
        self.client = ndb_client

    def __call__(self,environ,start_response):
        with self.client.context():
            return self.app(environ,start_response)

app = Flask(__name__)
app.wsgi_app = NDBMiddleware(app.wsgi_app)