"""
Offsite Spider Middleware
See documentation in docs/topics/spider-middleware.rst
"""
from __future__ import annotations
import logging
import re
import warnings
from typing import TYPE_CHECKING, Any, AsyncIterable, Iterable, Set
from scrapy import Spider, signals
from scrapy.crawler import Crawler
from scrapy.http import Request, Response
from scrapy.statscollectors import StatsCollector
from scrapy.utils.httpobj import urlparse_cached
if TYPE_CHECKING:
# typing.Self requires Python 3.11
from typing_extensions import Self
logger = logging.getLogger(__name__)
[docs]class OffsiteMiddleware:
def __init__(self, stats: StatsCollector):
self.stats: StatsCollector = stats
@classmethod
def from_crawler(cls, crawler: Crawler) -> Self:
assert crawler.stats
o = cls(crawler.stats)
crawler.signals.connect(o.spider_opened, signal=signals.spider_opened)
return o
def process_spider_output(
self, response: Response, result: Iterable[Any], spider: Spider
) -> Iterable[Any]:
return (r for r in result if self._filter(r, spider))
async def process_spider_output_async(
self, response: Response, result: AsyncIterable[Any], spider: Spider
) -> AsyncIterable[Any]:
async for r in result:
if self._filter(r, spider):
yield r
def _filter(self, request: Any, spider: Spider) -> bool:
if not isinstance(request, Request):
return True
if request.dont_filter or self.should_follow(request, spider):
return True
domain = urlparse_cached(request).hostname
if domain and domain not in self.domains_seen:
self.domains_seen.add(domain)
logger.debug(
"Filtered offsite request to %(domain)r: %(request)s",
{"domain": domain, "request": request},
extra={"spider": spider},
)
self.stats.inc_value("offsite/domains", spider=spider)
self.stats.inc_value("offsite/filtered", spider=spider)
return False
def should_follow(self, request: Request, spider: Spider) -> bool:
regex = self.host_regex
# hostname can be None for wrong urls (like javascript links)
host = urlparse_cached(request).hostname or ""
return bool(regex.search(host))
def get_host_regex(self, spider: Spider) -> re.Pattern[str]:
"""Override this method to implement a different offsite policy"""
allowed_domains = getattr(spider, "allowed_domains", None)
if not allowed_domains:
return re.compile("") # allow all by default
url_pattern = re.compile(r"^https?://.*$")
port_pattern = re.compile(r":\d+$")
domains = []
for domain in allowed_domains:
if domain is None:
continue
if url_pattern.match(domain):
message = (
"allowed_domains accepts only domains, not URLs. "
f"Ignoring URL entry {domain} in allowed_domains."
)
warnings.warn(message, URLWarning)
elif port_pattern.search(domain):
message = (
"allowed_domains accepts only domains without ports. "
f"Ignoring entry {domain} in allowed_domains."
)
warnings.warn(message, PortWarning)
else:
domains.append(re.escape(domain))
regex = rf'^(.*\.)?({"|".join(domains)})$'
return re.compile(regex)
def spider_opened(self, spider: Spider) -> None:
self.host_regex: re.Pattern[str] = self.get_host_regex(spider)
self.domains_seen: Set[str] = set()
class URLWarning(Warning):
pass
class PortWarning(Warning):
pass