Question

I have a weird error in my flask application.
Problem is that the code below works fine in the Flask development server but fails in the production server (Uwsgi+Nginx). The code’s intention is to retrieve an entire collection from mongoDb and serve it’s contents as JSON.

I am not using virtualenv as I work under a virtual machine and also, I don’t have any other projects running on that machine.
So the stack is like this:

Python
Flask
MongoDb->MongoEngine
Uwsgi
NginX

I have two models:

One for Company:

class Company(Document):
    name = StringField(max_length=50)
    ....

One for Campaigns:

class Campaign(Document):
    name = StringField(min_length=8)
    company = ReferenceField(Company)
    ....

The routing is done like this:

@app.route('/getjson', methods=['GET', 'POST'])
    def getJson():
        if request.method == 'GET':
        collection = request.args.get('collection')
        if collection == 'Campaign':
            return jsonify (getCampaign())

And the getCampaign() function goes like this:

def getCampaign():
    theCollection = Campaign.objects.all()
    theDict = {}
    for obj in x:
        dict_model = {
            obj.name:
            {
            'company': obj.company.name,
            ...
            }
    theDict.update(dict_model)
return theDict

This results in a nicely formated Json with “application/json” as Content-Type. Problem is when o try the same code on the production server it fails miserably throwing the following error!

    Traceback (most recent call last):
  File "/usr/local/lib/python2.6/dist-packages/flask/app.py", line 1518, in __call__
    return self.wsgi_app(environ, start_response)
  File "/usr/local/lib/python2.6/dist-packages/flask/app.py", line 1506, in wsgi_app
    response = self.make_response(self.handle_exception(e))
  File "/usr/local/lib/python2.6/dist-packages/flask/app.py", line 1504, in wsgi_app
    response = self.full_dispatch_request()
  File "/usr/local/lib/python2.6/dist-packages/flask/app.py", line 1264, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/usr/local/lib/python2.6/dist-packages/flask/app.py", line 1262, in full_dispatch_request
    rv = self.dispatch_request()
  File "/usr/local/lib/python2.6/dist-packages/flask/app.py", line 1248, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "./mobuy.py", line 58, in getJson
    return jsonify (getCampaign())
  File "./jsonOut.py", line 36, in getCampaign
    'company': obj.company.name,
  File "/usr/local/lib/python2.6/dist-packages/bson/dbref.py", line 88, in __getattr__
     raise AttributeError(key)
  AttributeError: name

Running ” ‘company’: “%s” % obj.dict ” throws this result:

"company":"{'_created': False, '_data': {'status': 3, 'startDate':
datetime.datetime(2012, 5, 23, 20, 22, 28, 42000), None: ObjectId('4fbd4704f65b813c5900000d'), 
'EndDate': datetime.datetime(2012, 5, 23, 20, 22, 28, 42000), 
'name': u'Campaign13', 'max_claimed': 39, 'text': u'a discount', 
'company': DBRef(u'company', ObjectId('4fbd36f2f65b813869000008')),
'image': u'http://www.Company8.com/image.jpg', 'Shops': [],
 'category': 5, 'id': None, 'coupons': []},
 '_id': ObjectId('4fbd4704f65b813c5900000d'), '_changed_fields': [],
 '_initialised': True}",

HELP! Why is this working in dev server and not working in Uwsgi??

Answer 1

The solution i found is, i went around the problem and queried the database with pymongo directly

#init pymongo dor dbfer quering as uwsgi fails miserably
connection = Connection()
db = connection.mobuy_test
company_collection = db.company
campaign_collection = db.campaign
for obj in Campaign.objects.all(): #the mongoengine queryset loop
    theId = campaign_collection.find_one({'_id':obj.id})['company'].id
    companyName = company_collection.find_one({'_id':theId})['name']
    dict_model = {
                  'campaign_name': obj.name,
                  'campaign_company':companyName
                   ...
                  }

Not sure if i used the pymongo query correctly but this works for now, only problem is, It’s Dirty.