您已经在Heroku中设置了MONGODB_URI环境变量来指向MongoHQ数据库。将代码添加到Flask应用的顶部：

import pymongo
from flask import Flask

app = Flask(__name__)

# Get the MongoHQ database connection string
mongo_uri = os.environ.get('MONGODB_URI')

# Connect to the MongoHQ database
client = pymongo.MongoClient(mongo_uri)

# Store the database connection in the Flask app's context
app.context_processor(lambda: {'db': client.test})

# In your tweet consuming app, replace the code
 self.db = pymongo.MongoClient().test
#To
self.db = app.context['db']
# it will ensure that your app is using the same database connection as the Flask app.