def open(self, spider):
self.spider = spider
self.setup()
self.dupefilter = RFPDupeFilter(self.redis_conn,
self.spider.name + ':dupefilter', self.rfp_timeout)
class DistributedScheduler(object):
'''
Scrapy request scheduler that utilizes Priority Queues
to moderate scrape requests within a distributed scrapy
cluster
'''
redis_conn = None # the redis connection
queue = None # the queue to use for crawling
spider = None # the spider using this scheduler
queue_class = None # the class to use for the queue
dupefilter = None # the redis dupefilter
item_retries = 0 # the number of extra tries to get an item
def __init__(self, server, persist, timeout, retries):
'''
Initialize the scheduler
'''
self.redis_conn = server
self.persist = persist
self.rfp_timeout = timeout
self.item_retires = retries
def setup(self):
'''
Used to initialize things when using mock
spider.name is not set yet
'''
self.queue = RedisPriorityQueue(self.redis_conn,
self.spider.name + ":queue")
@classmethod
def from_settings(cls, settings):
server = redis.Redis(host=settings.get('REDIS_HOST'),
port=settings.get('REDIS_PORT'))
persist = settings.get('SCHEDULER_PERSIST', True)
timeout = settings.get('DUPEFILTER_TIMEOUT', 600)
retries = settings.get('SCHEDULER_ITEM_RETRIES', 3)
return cls(server, persist, timeout, retries)
@classmethod
def from_crawler(cls, crawler):
return cls.from_settings(crawler.settings)
def open(self, spider):
self.spider = spider
self.setup()
self.dupefilter = RFPDupeFilter(self.redis_conn,
self.spider.name + ':dupefilter', self.rfp_timeout)
def close(self, reason):
if not self.persist:
self.dupefilter.clear()
self.queue.clear()
def is_blacklisted(self, appid, crawlid):
'''
Checks the redis blacklist for crawls that should not be propagated
either from expiring or stopped
@return: True if the appid crawlid combo is blacklisted
'''
key_check = '{appid}||{crawlid}'.format(appid=appid,
crawlid=crawlid)
redis_key = self.spider.name + ":blacklist"
return self.redis_conn.sismember(redis_key, key_check)
def enqueue_request(self, request):
'''
Pushes a request from the spider back into the queue
'''
if not request.dont_filter and self.dupefilter.request_seen(request):
return
req_dict = self.request_to_dict(request)
if not self.is_blacklisted(req_dict['meta']['appid'],
req_dict['meta']['crawlid']):
key = "{sid}:queue".format(sid=req_dict['meta']['spiderid'])
curr_time = time.time()
# insert if crawl never expires (0) or time < expires
if req_dict['meta']['expires'] == 0 or \
curr_time < req_dict['meta']['expires']:
self.queue.push(req_dict, req_dict['meta']['priority'])
def request_to_dict(self, request):
'''
Convert Request object to a dict.
modified from scrapy.utils.reqser
'''
req_dict = {
# urls should be safe (safe_string_url)
'url': request.url.decode('ascii'),
'method': request.method,
'headers': dict(request.headers),
'body': request.body,
'cookies': request.cookies,
'meta': request.meta,
'_encoding': request._encoding,
'priority': request.priority,
'dont_filter': request.dont_filter,
}
return req_dict
def find_item(self):
'''
Finds an item from the queue
'''
count = 0
while count <= self.item_retries:
item = self.queue.pop()
if item:
# very basic limiter
time.sleep(1)
return item
# we want the spiders to get slightly out of sync
# with each other for better performance
time.sleep(random.random())
count = count + 1
return None
def next_request(self):
'''
Logic to handle getting a new url request
'''
t = time.time()
item = self.find_item()
if item:
try:
req = Request(item['url'])
except ValueError:
# need absolute url
# need better url validation here
req = Request('http://' + item['url'])
if 'meta' in item:
item = item['meta']
# defaults
if "attrs" not in item:
item["attrs"] = {}
if "allowed_domains" not in item:
item["allowed_domains"] = ()
if "allow_regex" not in item:
item["allow_regex"] = ()
if "deny_regex" not in item:
item["deny_regex"] = ()
if "deny_extensions" not in item:
item["deny_extensions"] = None
if 'curdepth' not in item:
item['curdepth'] = 0
if "maxdepth" not in item:
item["maxdepth"] = 0
if "priority" not in item:
item['priority'] = 0
if "retry_times" not in item:
item['retry_times'] = 0
if "expires" not in item:
item['expires'] = 0
for key in ('attrs', 'allowed_domains', 'curdepth', 'maxdepth',
'appid', 'crawlid', 'spiderid', 'priority', 'retry_times',
'expires', 'allow_regex', 'deny_regex', 'deny_extensions'):
req.meta[key] = item[key]
return req
return None
def has_pending_requests(self):
'''
We never want to say we have pending requests
If this returns True scrapy sometimes hangs.
'''
return False