A news feed web service has the following code running on Google App Engine. During peak load, users report that they can see news articles they already viewed. What is the most likely cause of this problem?
import news
from flask import Flask, redirect, request
from flask.ext.api import status
from google.appengine.api import users
app = Flask(__name__)
sessions = {}
@app.route('/')
def homepage():
user = users.get_current_user()
if not user:
return "Invalid login", status.HTTP_401_UNAUTHORIZED
if user not in sessions:
sessions[user] = {'viewed': []}
news_articles = news.get_new_news(user, sessions[user]['viewed'])
sessions[user]['viewed'] += [n['id'] for n in news_articles]
return news.render(news_articles)
if __name__ == '__main__':
app.run()