Implementace prevodu HTML na PDF
Sluzba prijme adresu HTML dokumentu nebo HTML v tele requestu a vrati PDF. Navrzena pro dokumenty o stovkach az tisicich stranek. Rendering: - WeasyPrint jako vychozi engine, spravne CSS Paged Media, nizka pametova narocnost, bez JavaScriptu - Chromium pres Playwright pro dokumenty dokreslovane skripty - rezim auto s detekci skriptu a fallbackem pri selhani WeasyPrintu Velke dokumenty: - deleni na casti na strukturalnich hranicich, rez nikdy uvnitr tabulky nebo odstavce - dvoupruchodovy render obsahu se skutecnymi cisly stranek, pozice nadpisu se ctou z kotev hlasenych u kazde stranky - cislovani stranek bud pres CSS countery, nebo pres cislovaci vrstvu nastampovanou na hotove PDF, rozmer stranky se cte z vysledneho souboru - Chromium se restartuje po N jobech, nikdy vsak behem beziciho renderu API: - POST /convert synchronne, POST /jobs asynchronne se sledovanim stavu, stahovanim vysledku, rusenim a volitelnym callbackem - GET /health s overenim dostupnosti obou enginu a stavem fronty - OpenAPI respektuje prefix reverse proxy pres root_path Bezpecnost a provoz: - SSRF kontrola po DNS resolvu, na kazdem presmerovani a u vsech pozadavku prohlizece - nedostupne assety render nezastavi, ale hlasi se v odpovedi i v logu - fronta s omezenym poctem workeru, rozpracovane joby se pri ukonceni oznaci jako failed, nezmizi potichu - strukturovane JSON logovani s job_id - vsechny limity vypnute ve vychozim stavu Dockerfile je dvoufazovy, obsahuje zavislosti WeasyPrintu, Chromium a fonty s ceskou diakritikou. Autentizace zamerne neni implementovana, zpusob predavani neni domluveny. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
This commit is contained in:
JiriUhlir
co-authored by
Claude Opus 5
Claude Opus 5
parent
e3cc8f418b
commit
156289fe2d
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"""Fetching of the source document and of its assets.
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Both paths go through UrlGuard. Asset failures never abort the render, they are
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collected and reported back to the caller so nobody silently receives a PDF with
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missing images.
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"""
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from __future__ import annotations
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import io
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import logging
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from dataclasses import dataclass, field
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import httpx
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from ..config import Settings
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from ..errors import LimitExceededError, SourceUnavailableError
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from ..models import MissingAsset
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from .security import UrlGuard
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logger = logging.getLogger(__name__)
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USER_AGENT = "html-to-pdf/1.0 (AppFactory)"
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@dataclass
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class FetchedDocument:
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html: str
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base_url: str
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@dataclass
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class AssetReport:
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"""Collects assets that could not be loaded during a render."""
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missing: list[MissingAsset] = field(default_factory=list)
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_seen: set[str] = field(default_factory=set)
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def add(self, url: str, reason: str) -> None:
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if url in self._seen:
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return
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self._seen.add(url)
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self.missing.append(MissingAsset(url=url, reason=reason))
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logger.warning("Asset could not be loaded", extra={"asset_url": url, "reason": reason})
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def fetch_document(url: str, guard: UrlGuard, settings: Settings) -> FetchedDocument:
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"""Download the source HTML, validating every redirect hop."""
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current = url
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timeout = httpx.Timeout(settings.fetch_timeout_seconds)
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with httpx.Client(follow_redirects=False, timeout=timeout, headers={"User-Agent": USER_AGENT}) as client:
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for hop in range(settings.max_redirects + 1):
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guard.check(current)
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try:
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response = client.get(current)
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except httpx.HTTPError as exc:
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raise SourceUnavailableError(
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"Zdrojovy dokument se nepodarilo stahnout.",
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{"url": current, "reason": str(exc)},
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) from exc
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if response.is_redirect:
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location = response.headers.get("location")
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if not location:
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raise SourceUnavailableError(
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"Zdroj vratil presmerovani bez hlavicky Location.", {"url": current}
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)
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current = str(response.url.join(location))
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logger.info("Following redirect", extra={"hop": hop + 1, "target": current})
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continue
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if response.status_code >= 400:
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raise SourceUnavailableError(
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f"Zdrojovy dokument vratil HTTP {response.status_code}.",
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{"url": current, "status_code": response.status_code},
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)
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_check_size(len(response.content), settings)
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return FetchedDocument(html=response.text, base_url=str(response.url))
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raise SourceUnavailableError(
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"Prekrocen maximalni pocet presmerovani.",
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{"url": url, "max_redirects": settings.max_redirects},
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)
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def _check_size(size: int, settings: Settings) -> None:
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if settings.max_html_bytes and size > settings.max_html_bytes:
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raise LimitExceededError(
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"Zdrojovy dokument je vetsi nez nakonfigurovany limit MAX_HTML_BYTES.",
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{"size_bytes": size, "limit_bytes": settings.max_html_bytes},
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)
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def build_url_fetcher(guard: UrlGuard, report: AssetReport, allow_remote: bool, timeout_seconds: int):
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"""Return a WeasyPrint url_fetcher with SSRF checks and failure reporting."""
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from weasyprint import default_url_fetcher
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def fetcher(url: str, timeout: int = 10, ssl_context=None): # noqa: ARG001
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if url.startswith("data:"):
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return default_url_fetcher(url)
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if not allow_remote:
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report.add(url, "stahovani externich assetu je vypnute")
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return _empty_asset()
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try:
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guard.check(url)
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except Exception as exc: # noqa: BLE001 - reported, never silent
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report.add(url, f"zablokovano: {exc}")
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return _empty_asset()
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try:
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response = httpx.get(
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url,
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timeout=timeout_seconds,
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follow_redirects=False,
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headers={"User-Agent": USER_AGENT},
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)
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while response.is_redirect:
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location = response.headers.get("location")
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if not location:
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raise httpx.HTTPError("presmerovani bez hlavicky Location")
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target = str(response.url.join(location))
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guard.check(target)
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response = httpx.get(
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target,
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timeout=timeout_seconds,
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follow_redirects=False,
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headers={"User-Agent": USER_AGENT},
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)
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if response.status_code >= 400:
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report.add(url, f"HTTP {response.status_code}")
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return _empty_asset()
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return {
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"string": response.content,
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"mime_type": response.headers.get("content-type", "").split(";")[0] or None,
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"redirected_url": str(response.url),
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}
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except Exception as exc: # noqa: BLE001 - reported, never silent
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report.add(url, str(exc))
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return _empty_asset()
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return fetcher
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def _empty_asset() -> dict:
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"""Placeholder returned instead of a failed asset so the render continues."""
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return {"file_obj": io.BytesIO(b""), "mime_type": "application/octet-stream"}
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@dataclass
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class AssetGate:
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"""Per job gateway for everything the render pulls from the network."""
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guard: UrlGuard
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report: AssetReport
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allow_remote: bool = True
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timeout_seconds: int = 10
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def weasy_fetcher(self):
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return build_url_fetcher(self.guard, self.report, self.allow_remote, self.timeout_seconds)
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def allowed(self, url: str) -> tuple[bool, str]:
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"""Decide whether a browser initiated request may proceed."""
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if url.startswith("data:") or url.startswith("blob:") or url.startswith("about:"):
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return True, ""
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if not url.startswith(("http://", "https://")):
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return False, "nepovolene schema"
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if not self.allow_remote:
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return False, "stahovani externich assetu je vypnute"
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try:
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self.guard.check(url)
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except Exception as exc: # noqa: BLE001 - reported, never silent
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return False, str(exc)
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return True, ""
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