pferd/PFERD/crawl/http_crawler.py

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import asyncio
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from pathlib import Path, PurePath
from typing import Dict, List, Optional
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import aiohttp
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from aiohttp.client import ClientTimeout
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from ..auth import Authenticator
from ..config import Config
from ..logging import log
from ..utils import fmt_real_path
from ..version import NAME, VERSION
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from .crawler import Crawler, CrawlerSection
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class HttpCrawlerSection(CrawlerSection):
def http_timeout(self) -> float:
return self.s.getfloat("http_timeout", fallback=20)
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class HttpCrawler(Crawler):
COOKIE_FILE = PurePath(".cookies")
def __init__(
self,
name: str,
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section: HttpCrawlerSection,
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config: Config,
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shared_auth: Optional[Authenticator] = None,
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) -> None:
super().__init__(name, section, config)
self._authentication_id = 0
self._authentication_lock = asyncio.Lock()
self._request_count = 0
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self._http_timeout = section.http_timeout()
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self._cookie_jar_path = self._output_dir.resolve(self.COOKIE_FILE)
self._shared_cookie_jar_paths: Optional[List[Path]] = None
self._shared_auth = shared_auth
self._output_dir.register_reserved(self.COOKIE_FILE)
async def _current_auth_id(self) -> int:
"""
Returns the id for the current authentication, i.e. an identifier for the last
successful call to [authenticate].
This method must be called before any request that might authenticate is made, so the
HttpCrawler can properly track when [authenticate] can return early and when actual
authentication is necessary.
"""
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# We acquire the lock here to ensure we wait for any concurrent authenticate to finish.
# This should reduce the amount of requests we make: If an authentication is in progress
# all future requests wait for authentication to complete.
async with self._authentication_lock:
self._request_count += 1
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return self._authentication_id
async def authenticate(self, caller_auth_id: int) -> None:
"""
Starts the authentication process. The main work is offloaded to _authenticate, which
you should overwrite in a subclass if needed. This method should *NOT* be overwritten.
The [caller_auth_id] should be the result of a [_current_auth_id] call made *before*
the request was made. This ensures that authentication is not performed needlessly.
"""
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async with self._authentication_lock:
log.explain_topic("Authenticating")
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# Another thread successfully called authenticate in-between
# We do not want to perform auth again, so we return here. We can
# assume the other thread suceeded as authenticate will throw an error
# if it failed and aborts the crawl process.
if caller_auth_id != self._authentication_id:
log.explain(
"Authentication skipped due to auth id mismatch."
"A previous authentication beat us to the race."
)
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return
log.explain("Calling crawler-specific authenticate")
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await self._authenticate()
self._authentication_id += 1
# Saving the cookies after the first auth ensures we won't need to re-authenticate
# on the next run, should this one be aborted or crash
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self._save_cookies()
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async def _authenticate(self) -> None:
"""
Performs authentication. This method must only return normally if authentication suceeded.
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In all other cases it must either retry internally or throw a terminal exception.
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"""
raise RuntimeError("_authenticate() was called but crawler doesn't provide an implementation")
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def share_cookies(self, shared: Dict[Authenticator, List[Path]]) -> None:
if not self._shared_auth:
return
if self._shared_auth in shared:
self._shared_cookie_jar_paths = shared[self._shared_auth]
else:
self._shared_cookie_jar_paths = []
shared[self._shared_auth] = self._shared_cookie_jar_paths
self._shared_cookie_jar_paths.append(self._cookie_jar_path)
def _load_cookies(self) -> None:
log.explain_topic("Loading cookies")
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cookie_jar_path: Optional[Path] = None
if self._shared_cookie_jar_paths is None:
log.explain("Not sharing any cookies")
cookie_jar_path = self._cookie_jar_path
else:
log.explain("Sharing cookies")
max_mtime: Optional[float] = None
for path in self._shared_cookie_jar_paths:
if not path.is_file():
log.explain(f"{fmt_real_path(path)} is not a file")
continue
mtime = path.stat().st_mtime
if max_mtime is None or mtime > max_mtime:
log.explain(f"{fmt_real_path(path)} has newest mtime so far")
max_mtime = mtime
cookie_jar_path = path
else:
log.explain(f"{fmt_real_path(path)} has older mtime")
if cookie_jar_path is None:
log.explain("Couldn't find a suitable cookie file")
return
log.explain(f"Loading cookies from {fmt_real_path(cookie_jar_path)}")
try:
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self._cookie_jar.load(cookie_jar_path)
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except Exception as e:
log.explain("Failed to load cookies")
log.explain(str(e))
def _save_cookies(self) -> None:
log.explain_topic("Saving cookies")
try:
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log.explain(f"Saving cookies to {fmt_real_path(self._cookie_jar_path)}")
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self._cookie_jar.save(self._cookie_jar_path)
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except Exception as e:
log.warn(f"Failed to save cookies to {fmt_real_path(self._cookie_jar_path)}")
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log.warn(str(e))
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async def run(self) -> None:
self._request_count = 0
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self._cookie_jar = aiohttp.CookieJar()
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self._load_cookies()
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async with aiohttp.ClientSession(
headers={"User-Agent": f"{NAME}/{VERSION}"},
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cookie_jar=self._cookie_jar,
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timeout=ClientTimeout(total=self._http_timeout)
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) as session:
self.session = session
try:
await super().run()
finally:
del self.session
log.explain_topic(f"Total amount of HTTP requests: {self._request_count}")
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# They are saved in authenticate, but a final save won't hurt
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self._save_cookies()