def save_deal(deal_id):
'''
This allows a user to bookmark a deal, so the user can refer to the deal
at a later time
'''
msg = {}
user = get_current_user()
if str(deal_id) in user.deals_saved:
msg['status'] = 'error'
msg['message'] = 'you cannot save the same deal twice'
else:
user.deals_saved.append(deal_id)
user.save()
# noting that current user has bookmarked this deal
set_user_action_as_completed('save', deal_id, user.sequence_num)
# updating our redis cache
for sort in sorts:
r.delete("".join([user.name, '_', 'bookmarked', '_', sort]))
msg['status'] = 'success'
return jsonify(msg)
def vote_deal(deal_id):
'''
This function updates the number of votes of the deal by:
1) increasing num_votes by 1
2) add a new vote object into a deal's 'votes' list
'''
msg = {}
user = get_current_user()
if str(deal_id) in user.votes:
msg['status'] = 'error'
msg['message'] = 'you cannot vote for the same deal twice'
return jsonify(msg)
# we want to make sure that the user see's that his or her vote was counted
# right away w/o any delay. Hence, the following line is part of
# celery_tasks.upvote
else:
try:
user.deals_voted.append(str(deal_id))
user.save()
deal_queryset = Deal.objects(id=deal_id)
deal_queryset.update_one(inc__num_votes=1)
deal = deal_queryset.first()
# flushing redis cache to reflect the new vote count
remove_deal(deal.sequence_num)
# update redis cache: noting that current user has voted this deal in redis
set_user_action_as_completed('vote', deal_id, user.sequence_num)
for sort in sorts:
r.delete("".join([user.name, '_', 'liked', '_', sort]))
# update mongodb
celery_tasks.upvote.delay(deal_id, user.id, request.remote_addr)
msg['status'] = 'success'
return jsonify(msg)
except Exception as e:
print e
abort(404)
def store_list_of_deals(key, deal_seq_nums):
'''
Storing a list of deals that correpsonds to a deal query into redis.
This is used to reduce the need to query mongodb for a list of deals
that correponds to that query e.g. "get all deals in electronics less
than 1 wk old and sortd by popularity".
However, race condition may occur. Therefore, we use pipe.watch and
pipe.multi to ensure all redis transaction occur atomically. Also, if race
conditions occur, we will retry up to 25 times. It is ok if we quit after
25 tries because we will fallback to querying mongohq or whatever datastore
instead. It will be slower, but we will return the correct result.
'''
if len(deal_seq_nums) == 0:
# storing a -1 to denote that there are no deals associated with this key
pipe = r.pipeline()
pipe.rpush(key, 'None')
pipe.expire(key, cache_timeout)
pipe.execute()
else:
# creating a lock to prevent multiple threads from updating the same
# key. In other words, we use setnx as a lock to prevent
# race conditions between threads on updating the same key
#
# Also, we set the lock to expire in 10 seconds so if the lock
# owner dies prior to releasing the lock, the lock will be released
# automatically by redis
#
# Note to self:
# It is possible that a thread has acquired a lock but the thread
# dies before assigning an expiration to the lock or releases the lock.
#
# If that's the case, use the code below to ensure that we atomically
# grab the lock and set the lock with an expiration. Because of
# performance issues and potentially buggy code, the following piece
# of code is not used
#
# lock_obtained = False
# retries = 10
# done = False
# with r.pipeline() as pipe:
# while retries > 0 and not done:
# try:
# retries = retries - 1
# pipe.watch('lock')
# pipe.multi()
# pipe.setnx('lock', obtained)
# pipe.expires('lock', 10)
# lock_obtained = all(pipe.execute())
# done = True
# except WatchError
# continue
lock_expiration = 3 # 3 minutes
if r.setnx('lock', 'obtained'): # attemp to obtain lock
r.expire('lock', lock_expiration)
pipe = r.pipeline()
for num in deal_seq_nums:
pipe.rpush(key, num)
pipe.expire(key, cache_timeout)
pipe.rpush(set_of_deal_list_keys, key)
pipe.execute()
r.delete('lock') # release lock
def post_deal():
form = Deal_Form()
# if current_user is None:
# msg = {"status": "error", "message": "user not logged in"}
# return msg
if request.method == 'GET':
return render_template('post_deal.html', form=form)
elif request.method == 'POST':
if form.validate_on_submit():
title = request.form.get('title')
title = string.strip(title)
short_title = title[0:short_title_length - 1]
short_title = string_to_url_fix(short_title)
category = request.form.get('categories')
category = string.lower(category)
location = request.form.get('location', None)
if location == "":
location = None
if location and is_amazon_url(location):
location = gen_amazon_affiliate_url(location)
description = request.form.get('description', None)
user = get_current_user()
ip = request.remote_addr
new_deal = Deal(title=title, short_title=short_title,
location=location, category=category,
description=description, author_id=str(user.id),
num_votes=1, ip=ip)
new_deal.save()
new_deal_id = new_deal.id
# updating redis cache
store_deal(new_deal)
insert_new_deal_into_list(category, new_deal.sequence_num)
set_user_action_as_completed('vote', new_deal_id, user.sequence_num)
for sort in sorts:
r.delete("".join([user.name, '_', 'shared', '_', sort]))
# updating mongodb or datastore
user.deals_voted.append(str(new_deal_id))
user.deals_submitted.append(str(new_deal_id))
user.save()
celery_tasks.upvote.delay(new_deal_id, user.id, request.remote_addr)
#building this deal's url so to redirect the user
next = Href('/')
next = next('deals', new_deal.sequence_num, new_deal.short_title)
msg = {'status': 'success', 'redirect': next}
return jsonify(msg)
else:
#if form returns errors, return the errors to the users via js
msg = {"status": "error"}
if form.title.errors:
msg["title_error"] = form.title.errors[0]
if form.location.errors:
msg["location_error"] = form.location.errors[0]
if form.categories.errors:
msg["category_error"] = form.categories.errors[0]
if form.description.errors:
msg["description_error"] = form.description.errors[0]
return jsonify(msg)
else:
abort(404)
def store_list_of_deals(key, deal_seq_nums):
'''
Storing a list of deals that correpsonds to a deal query into redis.
This is used to reduce the need to query mongodb for a list of deals
that correponds to that query e.g. "get all deals in electronics less
than 1 wk old and sortd by popularity".
However, race condition may occur. Therefore, we use pipe.watch and
pipe.multi to ensure all redis transaction occur atomically. Also, if race
conditions occur, we will retry up to 25 times. It is ok if we quit after
25 tries because we will fallback to querying mongohq or whatever datastore
instead. It will be slower, but we will return the correct result.
'''
if len(deal_seq_nums) == 0:
# storing a -1 to denote that there are no deals associated with this key
pipe = r.pipeline()
pipe.rpush(key, 'None')
pipe.expire(key, cache_timeout)
pipe.execute()
else:
# creating a lock to prevent multiple threads from updating the same
# key. In other words, we use setnx as a lock to prevent
# race conditions between threads on updating the same key
#
# Also, we set the lock to expire in 10 seconds so if the lock
# owner dies prior to releasing the lock, the lock will be released
# automatically by redis
#
# Note to self:
# It is possible that a thread has acquired a lock but the thread
# dies before assigning an expiration to the lock or releases the lock.
#
# If that's the case, use the code below to ensure that we atomically
# grab the lock and set the lock with an expiration. Because of
# performance issues and potentially buggy code, the following piece
# of code is not used
#
# lock_obtained = False
# retries = 10
# done = False
# with r.pipeline() as pipe:
# while retries > 0 and not done:
# try:
# retries = retries - 1
# pipe.watch('lock')
# pipe.multi()
# pipe.setnx('lock', obtained)
# pipe.expires('lock', 10)
# lock_obtained = all(pipe.execute())
# done = True
# except WatchError
# continue
lock_expiration = 3 # 3 minutes
if r.setnx('lock', 'obtained'): # attemp to obtain lock
r.expire('lock', lock_expiration)
pipe = r.pipeline()
for num in deal_seq_nums:
pipe.rpush(key, num)
pipe.expire(key, cache_timeout)
pipe.rpush(set_of_deal_list_keys, key)
pipe.execute()
r.delete('lock') # release lock
