class Crawler(object):
""" Crawler - a simple web-crawler that follows internal
and external links.
It will save all its results in a DB, and will go on till it get to a defined max depth.
"""
def __init__(self, db_file='crawler.db'):
"""
:param db_file: The database file name to be saved
"""
self._url_scanner = UrlScanner()
self._db_manager = DBManager(db_file)
self._internal_urls_to_scan = []
self._external_urls_to_scan = []
self._max_page_depth = None
self._max_external_sites_page_depth = None
self._domain = None
def crawl(self, url, max_page_depth=5, max_external_sites_page_depth=4, request_rate_limit=4):
"""
Will crawl a given url up to max_page_depth and max_external_sites_page_depth on a max rate of
request_rate_limit.
:param url: The to-be crawled url
:param max_page_depth: Max internal (same-domain) depth
:param max_external_sites_page_depth: Max external (different-domain) depth
:param request_rate_limit: Up to n requests at once
:return: List of Url objects (See schemas/url.py)
"""
self._url_scanner.set_request_limit(request_rate_limit)
self._max_page_depth = max_page_depth
self._max_external_sites_page_depth = max_external_sites_page_depth
self._domain = get_domain(url)
self._internal_urls_to_scan.append(url)
self._crawl_internal_urls()
self._crawl_external_urls()
return self._get_crawled_urls()
def _get_crawled_urls(self):
return self._db_manager.get_crawled_urls()
def _crawl_internal_urls(self):
while self._internal_urls_to_scan and self._max_page_depth:
child_urls = self._url_scanner.scan(self._internal_urls_to_scan)
child_urls = list(set(child_urls) - set([x.url for x in self._db_manager.get_crawled_urls()]))
self._internal_urls_to_scan = get_same_domain_urls(self._domain, child_urls)
self._external_urls_to_scan.extend(get_external_urls(self._domain, child_urls))
url_objects = [{'url': url, 'crawl_time': datetime.now()} for url in self._internal_urls_to_scan]
self._db_manager.update(url_objects)
self._max_page_depth -= 1
def _crawl_external_urls(self):
while self._external_urls_to_scan and self._max_external_sites_page_depth:
self._external_urls_to_scan = self._url_scanner.scan(self._external_urls_to_scan)
self._external_urls_to_scan = list(
set(self._external_urls_to_scan) - set([x.url for x in self._db_manager.get_crawled_urls()]))
url_objects = [{'url': url, 'crawl_time': datetime.now()} for url in self._external_urls_to_scan]
self._db_manager.update(url_objects)
self._max_external_sites_page_depth -= 1
class DBManagerTests(TestBase):
def setUp(self):
self.db_manager = DBManager('test.db')
def test_insertion_sanity(self):
self.db_manager.update([
{'url': 'http://example.com/', 'crawl_time': datetime.now()},
{'url': 'http://example.com/a.html', 'crawl_time': datetime.now()}])
crawled = self.db_manager.get_crawled_urls()
expected = ['http://example.com/', 'http://example.com/a.html']
self.assertEqual([x.url for x in crawled], expected)
