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110 lines
4.3 KiB
Python
110 lines
4.3 KiB
Python
import asyncio
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from pathlib import PurePath
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from typing import Optional
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import aiohttp
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from .config import Config
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from .crawler import Crawler, CrawlerSection
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from .logging import log
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from .utils import fmt_real_path
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from .version import NAME, VERSION
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class HttpCrawler(Crawler):
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COOKIE_FILE = PurePath(".cookies")
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def __init__(
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self,
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name: str,
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section: CrawlerSection,
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config: Config,
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) -> None:
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super().__init__(name, section, config)
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self._cookie_jar_path = self._output_dir.resolve(self.COOKIE_FILE)
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self._output_dir.register_reserved(self.COOKIE_FILE)
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self._authentication_id = 0
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self._authentication_lock = asyncio.Lock()
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self._current_cookie_jar: Optional[aiohttp.CookieJar] = None
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self._request_count = 0
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async def _current_auth_id(self) -> int:
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"""
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Returns the id for the current authentication, i.e. an identifier for the last
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successful call to [authenticate].
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This method must be called before any request that might authenticate is made, so the
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HttpCrawler can properly track when [authenticate] can return early and when actual
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authentication is necessary.
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"""
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# We acquire the lock here to ensure we wait for any concurrent authenticate to finish.
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# This should reduce the amount of requests we make: If an authentication is in progress
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# all future requests wait for authentication to complete.
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async with self._authentication_lock:
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self._request_count += 1
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return self._authentication_id
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async def authenticate(self, caller_auth_id: int) -> None:
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"""
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Starts the authentication process. The main work is offloaded to _authenticate, which
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you should overwrite in a subclass if needed. This method should *NOT* be overwritten.
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The [caller_auth_id] should be the result of a [_current_auth_id] call made *before*
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the request was made. This ensures that authentication is not performed needlessly.
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"""
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async with self._authentication_lock:
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# Another thread successfully called authenticate in-between
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# We do not want to perform auth again, so we return here. We can
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# assume the other thread suceeded as authenticate will throw an error
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# if it failed and aborts the crawl process.
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if caller_auth_id != self._authentication_id:
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return
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await self._authenticate()
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self._authentication_id += 1
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# Saving the cookies after the first auth ensures we won't need to re-authenticate
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# on the next run, should this one be aborted or crash
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await self._save_cookies()
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async def _authenticate(self) -> None:
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"""
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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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"""
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raise RuntimeError("_authenticate() was called but crawler doesn't provide an implementation")
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async def _save_cookies(self) -> None:
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log.explain_topic("Saving cookies")
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if not self._current_cookie_jar:
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log.explain("No cookie jar, save aborted")
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return
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try:
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self._current_cookie_jar.save(self._cookie_jar_path)
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log.explain(f"Cookies saved to {fmt_real_path(self._cookie_jar_path)}")
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except Exception:
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log.warn(f"Failed to save cookies to {fmt_real_path(self._cookie_jar_path)}")
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async def run(self) -> None:
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self._current_cookie_jar = aiohttp.CookieJar()
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self._request_count = 0
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try:
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self._current_cookie_jar.load(self._cookie_jar_path)
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except Exception:
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pass
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async with aiohttp.ClientSession(
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headers={"User-Agent": f"{NAME}/{VERSION}"},
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cookie_jar=self._current_cookie_jar,
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) as session:
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self.session = session
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try:
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await super().run()
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finally:
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del self.session
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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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await self._save_cookies()
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