mirror of
https://github.com/Garmelon/PFERD.git
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bd9d7efe64
Thank you mypy, very cool. These types make things *so much better*. They don't just complicate everything and don't really help because they can not detect that an element queried by a tag is no navigable string...
282 lines
12 KiB
Python
282 lines
12 KiB
Python
import asyncio
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import http.cookies
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import ssl
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from datetime import datetime
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from pathlib import Path, PurePath
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from typing import Any, Dict, List, Optional, Tuple, cast
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import aiohttp
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import certifi
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from aiohttp.client import ClientTimeout
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from bs4 import Tag
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from ..auth import Authenticator
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from ..config import Config
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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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from .crawler import Crawler, CrawlerSection
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ETAGS_CUSTOM_REPORT_VALUE_KEY = "etags"
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class HttpCrawlerSection(CrawlerSection):
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def http_timeout(self) -> float:
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return self.s.getfloat("http_timeout", fallback=20)
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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: HttpCrawlerSection,
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config: Config,
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shared_auth: Optional[Authenticator] = None,
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) -> None:
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super().__init__(name, section, config)
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self._authentication_id = 0
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self._authentication_lock = asyncio.Lock()
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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)
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self._shared_cookie_jar_paths: Optional[List[Path]] = None
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self._shared_auth = shared_auth
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self._output_dir.register_reserved(self.COOKIE_FILE)
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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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log.explain_topic("Authenticating")
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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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log.explain(
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"Authentication skipped due to auth id mismatch."
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"A previous authentication beat us to the race."
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)
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return
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log.explain("Calling crawler-specific authenticate")
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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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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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def share_cookies(self, shared: Dict[Authenticator, List[Path]]) -> None:
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if not self._shared_auth:
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return
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if self._shared_auth in shared:
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self._shared_cookie_jar_paths = shared[self._shared_auth]
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else:
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self._shared_cookie_jar_paths = []
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shared[self._shared_auth] = self._shared_cookie_jar_paths
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self._shared_cookie_jar_paths.append(self._cookie_jar_path)
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def _load_cookies_from_file(self, path: Path) -> None:
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jar: Any = http.cookies.SimpleCookie()
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with open(path, encoding="utf-8") as f:
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for i, line in enumerate(f):
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# Names of headers are case insensitive
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if line[:11].lower() == "set-cookie:":
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jar.load(line[11:])
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else:
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log.explain(f"Line {i} doesn't start with 'Set-Cookie:', ignoring it")
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self._cookie_jar.update_cookies(jar)
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def _save_cookies_to_file(self, path: Path) -> None:
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jar: Any = http.cookies.SimpleCookie()
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for morsel in self._cookie_jar:
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jar[morsel.key] = morsel
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with open(path, "w", encoding="utf-8") as f:
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f.write(jar.output(sep="\n"))
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f.write("\n") # A trailing newline is just common courtesy
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def _load_cookies(self) -> None:
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log.explain_topic("Loading cookies")
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cookie_jar_path: Optional[Path] = None
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if self._shared_cookie_jar_paths is None:
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log.explain("Not sharing any cookies")
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cookie_jar_path = self._cookie_jar_path
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else:
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log.explain("Sharing cookies")
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max_mtime: Optional[float] = None
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for path in self._shared_cookie_jar_paths:
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if not path.is_file():
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log.explain(f"{fmt_real_path(path)} is not a file")
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continue
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mtime = path.stat().st_mtime
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if max_mtime is None or mtime > max_mtime:
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log.explain(f"{fmt_real_path(path)} has newest mtime so far")
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max_mtime = mtime
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cookie_jar_path = path
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else:
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log.explain(f"{fmt_real_path(path)} has older mtime")
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if cookie_jar_path is None:
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log.explain("Couldn't find a suitable cookie file")
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return
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log.explain(f"Loading cookies from {fmt_real_path(cookie_jar_path)}")
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try:
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self._load_cookies_from_file(cookie_jar_path)
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except Exception as e:
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log.explain("Failed to load cookies")
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log.explain(str(e))
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def _save_cookies(self) -> None:
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log.explain_topic("Saving cookies")
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try:
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log.explain(f"Saving cookies to {fmt_real_path(self._cookie_jar_path)}")
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self._save_cookies_to_file(self._cookie_jar_path)
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except Exception as e:
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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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@staticmethod
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def get_folder_structure_from_heading_hierarchy(file_link: Tag, drop_h1: bool = False) -> PurePath:
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"""
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Retrieves the hierarchy of headings associated with the give file link and constructs a folder
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structure from them.
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<h1> level headings usually only appear once and serve as the page title, so they would introduce
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redundant nesting. To avoid this, <h1> headings are ignored via the drop_h1 parameter.
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"""
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def find_associated_headings(tag: Tag, level: int) -> PurePath:
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if level == 0 or (level == 1 and drop_h1):
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return PurePath()
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level_heading = cast(Optional[Tag], tag.find_previous(name=f"h{level}"))
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if level_heading is None:
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return find_associated_headings(tag, level - 1)
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folder_name = level_heading.get_text().strip()
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return find_associated_headings(level_heading, level - 1) / folder_name
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# start at level <h3> because paragraph-level headings are usually too granular for folder names
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return find_associated_headings(file_link, 3)
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def _get_previous_etag_from_report(self, path: PurePath) -> Optional[str]:
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"""
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If available, retrieves the entity tag for a given path which was stored in the previous report.
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"""
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if not self._output_dir.prev_report:
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return None
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etags = self._output_dir.prev_report.get_custom_value(ETAGS_CUSTOM_REPORT_VALUE_KEY) or {}
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return etags.get(str(path))
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def _add_etag_to_report(self, path: PurePath, etag: Optional[str]) -> None:
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"""
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Adds an entity tag for a given path to the report's custom values.
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"""
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if not etag:
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return
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etags = self._output_dir.report.get_custom_value(ETAGS_CUSTOM_REPORT_VALUE_KEY) or {}
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etags[str(path)] = etag
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self._output_dir.report.add_custom_value(ETAGS_CUSTOM_REPORT_VALUE_KEY, etags)
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async def _request_resource_version(self, resource_url: str) -> Tuple[Optional[str], Optional[datetime]]:
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"""
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Requests the ETag and Last-Modified headers of a resource via a HEAD request.
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If no entity tag / modification date can be obtained, the according value will be None.
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"""
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try:
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async with self.session.head(resource_url) as resp:
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if resp.status != 200:
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return None, None
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etag_header = resp.headers.get("ETag")
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last_modified_header = resp.headers.get("Last-Modified")
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last_modified = None
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if last_modified_header:
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try:
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# https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Last-Modified#directives
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datetime_format = "%a, %d %b %Y %H:%M:%S GMT"
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last_modified = datetime.strptime(last_modified_header, datetime_format)
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except ValueError:
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# last_modified remains None
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pass
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return etag_header, last_modified
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except aiohttp.ClientError:
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return None, None
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async def run(self) -> None:
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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(
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headers={"User-Agent": f"{NAME}/{VERSION}"},
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cookie_jar=self._cookie_jar,
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connector=aiohttp.TCPConnector(ssl=ssl.create_default_context(cafile=certifi.where())),
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timeout=ClientTimeout(
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# 30 minutes. No download in the history of downloads was longer than 30 minutes.
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# This is enough to transfer a 600 MB file over a 3 Mib/s connection.
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# Allowing an arbitrary value could be annoying for overnight batch jobs
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total=15 * 60,
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connect=self._http_timeout,
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sock_connect=self._http_timeout,
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sock_read=self._http_timeout,
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),
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# See https://github.com/aio-libs/aiohttp/issues/6626
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# Without this aiohttp will mangle the redirect header from Shibboleth, invalidating the
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# passed signature. Shibboleth will not accept the broken signature and authentication will
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# fail.
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requote_redirect_url=False
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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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self._save_cookies()
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