wayback-python prototyping

liveweb.py

"""Prototype of liveweb proxy.
"""
def get_recent_crawl_location(url):
    """Looks at memcache to find the location of the recent crawl of the given URL.
    """
    return memcache_client.get(md5sum(url))

def fetch(url):
    """Fetches a url from liveweb. 

    If the url is cralwed very recently, returns that instead of fetching again.
    """
    location = get_recent_crawl_locaiton(url)
    if location:
        filename, offset, size = location.split()
        content = read_file(filename, offset, size)
    else:
        # warcproxy is a script written by Kenji
        # We need to modify it to update memcache with offset info.
        content = warcproxy.fetch(url)
    return content

query_urldb.py

def fetch_url(url, timestamp):
    if url.endswith('*'):
        return fetch_prefix_matches(url, timestamp)
    else:
        return fetch_wayback_content(url, timestamp)


def fetch_prefix_matches(prefix_url, timestamp=None):
    assert prefix_url.endswith('*')

    match_list = query_urldb(prefix_url)

    if match_list and timestamp:
        match_list = filter_by_time(match_list, timestamp)

    return match_list


def fetch_wayback_content(url, timestamp):
    match_list = query_urldb(url)
    closest_match = get_closest_capture(match_list, timestamp)

    if closest_match is None:
        return None

    return fetch_from_cluster(closest_match)

robots.py

"""Robots.txt cache.

Recently used robots.txt files are cached in memcache.
"""
from robotparser import RobotFileParser
import query_urldb as urldb
import liveweb

def get_robotstxt(host):
    """Returns the contents of robots.txt file for given host from the wayback 
    machine.
    """
    txt = memcache.get(host)
    if not txt:
        url = "http://%s/robots.txt" % host
        timestamp = "latest-timestamp-here"
        txt = urldb.fetch_wayback_content(url, timestamp) or liveweb.fetch(url)
        memcache.put(host, txt)
    return txt

def is_allowed(url):
    """Returns True if robots.txt allows waybackmachine to fetch/display the given URL.
    """
    txt = get_robotstxt(get_host(url))
    
    parser = RobotFileParser()
    parser.parse(txt.splitlines())
    
    return parser.can_fetch("ia_archiver", url)
    

webapp.py

"""Prototype of wayback webapp.
"""

import robots
import query_urldb as urldb
import liveweb

def index():
     return render_template("index.html")

def calendar(timestamp, url):
    assert "*" in timestamp
    if not robots.allowed(url):
        return render_template("norobots.html", url)

    data = urldb.query(url, timestamp)
    if data:
        return render_template("calendar.html", url, data)
    else:
        return render_template("not_archived.html", url)

def page(timestamp, url):
    assert "*" not in timestamp
    
    if not robots.allowed(url):
        return render_template("norobots.html", url)

    data = urldb.fetch_wayback_content(url, timestamp) or liveweb.fetch(url)
    status, mimetype, body = parse_response(data)

    # Handle non 200 status
    if status != 200:
        return render_template("non200.html", status, url)

    # convert links and insert wayback header for html documents
    if mimetype == "text/html":
        body = rewrite_page(body, timestamp)
    return body