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api.py
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api.py
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import datetime
import json
import math
import re
import requests
import time
import threading
from bs4 import BeautifulSoup
from flask import Flask, request, logging, abort, Response
import werkzeug.exceptions
app = Flask(__name__)
logger = logging.create_logger(app)
logger.root.setLevel('INFO')
# (for the sake of an example) local kv-storage for asynk tasks
JOBS = {}
def try_challenge(initial_response):
"""Handle Cloudflare challenge"""
# not implemented
logger.warning('Status code 503, not handled')
return False, 'Completed, status code %s' % (initial_response.status_code), None
def try_get_request(url, retry_on_rate_limit=True):
"""Send GET request.
Args:
str url: URL to send request to
bool retry_on_rate_limit: when True, if rate limit is encountered on the remote, we will wait and retry
"""
logger.info('Requesting %s' % (url))
try:
response = requests.get(url)
except requests.exceptions.MissingSchema:
return False, 'Failed, invalid URL', None
except requests.exceptions.ConnectionError:
return False, 'Failed, connection error', None
logger.info('Got response, status code %d' % (response.status_code))
if response.status_code == 200:
return True, 'Completed, status code %s' % (response.status_code), response
elif response.status_code == 503: # challenge?
return try_challenge(response)
elif response.status_code == 429: # rate limit?
retry_after = int(response.headers['retry-after'])
logger.warning('Rate limit allows retrying in %d seconds' % (retry_after))
if retry_on_rate_limit:
logger.info('Retrying in %d s' % (retry_after))
time.sleep(retry_after)
return try_get_request(url, retry_on_rate_limit=False)
logger.warning('Will not retry, moving on')
return False, 'Completed, status code %s' % (response.status_code), None
def get_rating_distribution(soup):
"""Locate and parse specific section of a page containg review rating distribution.
Args:
BeautifulSoup soup: object representing parsed HTML page
"""
script_child = soup.find(string=re.compile(r'^window.__ssr_data'))
if script_child is None:
logger.warning('Could not find section to extract ratingDistribution from')
return []
script_text = str(script_child)
ssr_data_statement = script_text[script_text.find("window.__ssr_data='"):script_text.find("}';", script_text.find("window.__ssr_data='"))+2]
ssr_data = ssr_data_statement[19:-1].replace('\\\\n', '\n').replace('\\\\', '$backslash').replace('\\', '').replace('$backslash', '\\')
try:
ssr_json = json.loads(ssr_data, strict=False)
rating_distribution = ssr_json['reduxAsyncConnect']['itemsMap']['listingPageAsyncDataContainer']['data']['listing']['statistics']['ratingDistribution']
except:
logger.warning('Found relevant section, but could not extract ratingDistribution')
return []
logger.info('Extracted ratingDistribution=%s' % (str(rating_distribution)))
return rating_distribution
def parse_html(html, get_ssr_data, url, response_description):
"""Parse HTML content (supposedly returned as some response.text)
Args:
str html: text to parse (expecting HTML page with reviews)
bool get_ssr_data: when True, specific part of the page containing review rating distribution will be parsed as well
str url: URL from where HTML was originally retrieved
str response_description: message from helper function that was sending HTTP request
"""
total_reviews, rating_distribution, reviews = 0, [], {}
soup = BeautifulSoup(html, 'html.parser')
content_element = soup.find(name='script', attrs={'data-react-helmet': 'true'})
if content_element is None: # page is likely invalid
msg = 'Page is invalid: %s' % (url)
logger.warning(msg)
return response_description, msg, total_reviews, rating_distribution, reviews
if get_ssr_data:
rating_distribution = get_rating_distribution(soup)
content = json.loads(content_element.text)
if 'aggregateRating' not in content: # page is likely invalid
msg = 'Page is invalid: %s' % (url)
logger.warning(msg)
return response_description, msg, total_reviews, rating_distribution, reviews
total_reviews = content['aggregateRating']['reviewCount']
if total_reviews > 0 and 'review' in content:
for review in content['review']:
reviews[review['url']] = {'title': review['headline'], 'content': review['reviewBody'], 'author_name': review['author']['name'], 'author_uri': review['author']['sameAs'], 'rating': review['reviewRating']['ratingValue'], 'date': review['datePublished']}
msg = 'Page %s: reviewCount=%d; extracted from page: %d' % (url, total_reviews, len(reviews))
logger.info(msg)
return response_description, msg, total_reviews, rating_distribution, reviews
def get_reviews_from_page(url, retry_on_rate_limit, get_ssr_data=False):
"""Request single page and parse it.
Args:
str url: URL of the page to parse
bool retry_on_rate_limit: when True, if rate limit is encountered on the remote, we will wait and retry
bool get_ssr_data: when True, specific part of the page containing review rating distribution will be parsed as well
"""
success, response_description, response = try_get_request(url, retry_on_rate_limit)
if not success:
msg = 'Failed to load page %s' % (url)
logger.warning(msg)
return response_description, msg, 0, [], {}
return parse_html(response.text, get_ssr_data, url, response_description)
def page_url(base_url, star_rating, page_number, sort_by_oldest=False):
"""Construct URL using provided parameters.
Args:
str base_url: URL stripped of any parameters
int star_rating: review rating
int page_number: page number
bool sort_by_oldest: when True, sort reviews 'oldest to newest' first before retrieving a page
"""
if sort_by_oldest:
url = '%s?sortBy=oldest&rating=%d' % (base_url, star_rating)
else:
url = '%s?rating=%d' % (base_url, star_rating)
if page_number > 1:
url = '%s&page=%d' % (url, page_number)
logger.info('Will request rating=%d, page=%d, ordered %s first (%s)' % (star_rating, page_number, 'oldest' if sort_by_oldest else 'newest', url))
return url
def get_reviews(url, crawl=False, sort_by_oldest=False, retry_on_rate_limit=False, page_limit=0):
"""Process one or more pages starting with specified URL and return collected reviews.
Args:
str url: URL to process
bool crawl: when True and there are more reviews than fit single page, other pages with same base URL will be processed as well
bool sort_by_oldest: when True, additional pages will be loaded when reviews are sorted 'oldest to newest'
bool retry_on_rate_limit: when True, if rate limit is encountered on the remote, we will wait and retry
int page_limit: when >= 0, limit number of requested pages per each star rating to this number
"""
# get first page and check if we have all the reviews with one shot
last_response_description, last_msg, total_reviews, rating_distribution, reviews = get_reviews_from_page(url, retry_on_rate_limit, get_ssr_data=True)
if total_reviews == 0:
logger.warning('Did not get any reviews from requested page')
return {'http_response': last_response_description, 'job_status': last_msg, 'data': reviews}
elif total_reviews == len(reviews) or not crawl:
logger.info('%s' % ('Got all reviews in one go' if crawl else 'Got reviews from requested page (will not look further)'))
return {'http_response': last_response_description, 'job_status': last_msg, 'data': reviews}
logger.info('Reviews take more than 1 page, will try crawling')
# stratify by star rating, then by page number
if not rating_distribution:
rating_distribution = [total_reviews] * 5
base_url = url.split('?')[0]
got_reviews = {}
processed_pages = {}
for star_rating in range(1, 6):
if rating_distribution[star_rating-1] == 0:
continue
expected_pages_count = math.ceil(rating_distribution[star_rating-1] / 25)
if star_rating in processed_pages and processed_pages[star_rating] == expected_pages_count:
logger.info('Already got all pages for rating=%d' % (star_rating))
continue
logger.info('Star rating %d: expecting %d page%s' % (star_rating, expected_pages_count, 's' if expected_pages_count != 1 else ''))
for page_number in range(1, expected_pages_count+1):
if page_limit > 0 and page_number > page_limit:
logger.warning('Will not process pages beyond page %d' % page_limit)
break
next_url = page_url(base_url, star_rating, page_number, sort_by_oldest)
try:
last_response_description, last_msg, _, _, got_reviews = get_reviews_from_page(next_url, retry_on_rate_limit)
processed_pages[star_rating] = page_number
except:
pass
reviews.update(got_reviews)
logger.info('Total reviews collected so far: %d (%s)' % (len(reviews), url))
logger.info('Got %d reviews from %s' % (len(reviews), url))
return {'http_response': last_response_description, 'job_status': last_msg, 'data': reviews}
def run_job(job_id, method, *args, **kwargs):
"""Wrap get_reviews() function in a job.
Args:
str job_id: ID of a job to store
object method: procedure to execute (expected to return iterable with at least 3 items)
*args, **kwargs: parameters for method
"""
global JOBS
JOBS[job_id] = {'http_response': 'N/A', 'job_status': 'In progress', 'data': {}}
result = method(*args, **kwargs)
JOBS[job_id] = result
# Views
@app.route('/', methods=['GET', 'POST'])
def scrape():
"""Get parameters and either parse single page right away and return the results,
or start job in a separate thread and return endpoint to retrieve the results later.
"""
global JOBS
if request.method == 'GET':
# parse single page
url = request.args['url']
result = get_reviews(url=url)
return result
elif request.method == 'POST':
# promise to parse what is requested, and execute in a separate thread
parameters = {}
try:
parameters = request.get_json()
except werkzeug.exceptions.BadRequest:
return Response("{'status_code': '400', 'message': 'request parameters have not been provided'}", status=400, mimetype='application/json')
url = parameters['url'] if 'url' in parameters else None
crawl = parameters['crawl'].lower() == 'true' if 'crawl' in parameters else False
sort_oldest_first = parameters['oldest_first'].lower() == 'true' if 'oldest_first' in parameters else False
retry_on_rate_limit = parameters['retry_on_rate_limit'].lower() == 'true' if 'retry_on_rate_limit' in parameters else False
page_limit = int(parameters['page_limit']) if 'page_limit' in parameters and parameters['page_limit'].isdigit() else 0
if url is None:
return Response("{'status_code': '400', 'message': 'remote URL has not been provided'}", status=400, mimetype='application/json')
if not url.startswith('https://www.productreview.com.au/listings/'):
return Response("{'status_code': '400', 'message': 'remote URL is invalid'}", status=400, mimetype='application/json')
job_id = str(datetime.datetime.timestamp(datetime.datetime.now()))
JOBS[job_id] = {'http_response': 'N/A', 'job_status': 'Requested', 'data': {}}
t = threading.Thread(target=run_job, args=(job_id, get_reviews, url, crawl, sort_oldest_first, retry_on_rate_limit, page_limit))
t.run()
return {'fetch_results_at': '/result?job_id=%s' % (str(job_id))}
abort(400)
@app.route('/jobs', methods=['GET'])
def result():
"""Return list of async jobs"""
global JOBS
return {'jobs': list(JOBS.keys())}
@app.route('/result', methods=['GET'])
def jobs():
"""Return result of a job done asynchronously"""
global JOBS
job_id = request.args['job_id']
if job_id in JOBS:
return JOBS[job_id]
abort(400)
if __name__ == '__main__':
app.run(port=5000)