Reuse dl/cl for I/O retries in ILIAS crawler

This commit is contained in:
I-Al-Istannen 2021-05-23 00:28:27 +02:00
parent 8ac85ea0bd
commit 53e031d9f6

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@ -72,11 +72,11 @@ AWrapped = TypeVar("AWrapped", bound=Callable[..., Awaitable[None]])
def _iorepeat(attempts: int, name: str) -> Callable[[AWrapped], AWrapped]: def _iorepeat(attempts: int, name: str) -> Callable[[AWrapped], AWrapped]:
def decorator(f: AWrapped) -> AWrapped: def decorator(f: AWrapped) -> AWrapped:
async def wrapper(self: "HttpCrawler", *args: Any, **kwargs: Any) -> None: async def wrapper(*args: Any, **kwargs: Any) -> None:
last_exception: Optional[BaseException] = None last_exception: Optional[BaseException] = None
for round in range(attempts): for round in range(attempts):
try: try:
await f(self, *args, **kwargs) await f(*args, **kwargs)
return return
except aiohttp.ContentTypeError: # invalid content type except aiohttp.ContentTypeError: # invalid content type
raise CrawlWarning("ILIAS returned an invalid content type") raise CrawlWarning("ILIAS returned an invalid content type")
@ -97,6 +97,43 @@ def _iorepeat(attempts: int, name: str) -> Callable[[AWrapped], AWrapped]:
return decorator return decorator
def _wrap_io_in_warning(name: str) -> Callable[[AWrapped], AWrapped]:
"""
Wraps any I/O exception in a CrawlWarning.
"""
return _iorepeat(1, name)
# Crawler control flow:
#
# crawl_desktop -+
# |
# crawl_course --+
# |
# +- crawl_url <-+
# |
# |
# | @_wrap_io_exception # does not need to retry as children acquire bars
# +> crawl_ilias_element -+
# ^ |
# | @_io_repeat | # retries internally (before the bar)
# +- crawl_ilias_page <---+
# | |
# +> get_page | # Handles and retries authentication
# |
# @_io_repeat | # retries internally (before the bar)
# +- download_link <---+
# | |
# +> resolve_target | # Handles and retries authentication
# |
# @_io_repeat | # retries internally (before the bar)
# +- download_video <---+
# | |
# | @_io_repeat | # retries internally (before the bar)
# +- download_file <---+
# |
# +> stream_from_url # Handles and retries authentication
class KitIliasWebCrawler(HttpCrawler): class KitIliasWebCrawler(HttpCrawler):
def __init__( def __init__(
self, self,
@ -169,6 +206,9 @@ class KitIliasWebCrawler(HttpCrawler):
if not cl: if not cl:
return return
@_iorepeat(3, "crawling folder")
async def impl() -> None:
assert cl # The function is only reached when cl is not None
tasks = [] tasks = []
async with cl: async with cl:
soup = await self._get_page(url) soup = await self._get_page(url)
@ -177,10 +217,19 @@ class KitIliasWebCrawler(HttpCrawler):
for child in page.get_child_elements(): for child in page.get_child_elements():
tasks.append(self._handle_ilias_element(path, child)) tasks.append(self._handle_ilias_element(path, child))
# The only point an I/O exception can be thrown is in `get_page`.
# If that happens, no task was spawned yet. Therefore, we only retry
# this method without having spawned a single task. Due to this we do
# not need to cancel anything or worry about this gather call or the forks
# further up.
await asyncio.gather(*tasks) await asyncio.gather(*tasks)
await impl()
@anoncritical @anoncritical
@_iorepeat(3, "ILIAS element crawling") # Shouldn't happen but this method must never raise an I/O error as that might interfere with
# handle_ilias_page
@_wrap_io_in_warning("ilias element handling")
async def _handle_ilias_element(self, parent_path: PurePath, element: IliasPageElement) -> None: async def _handle_ilias_element(self, parent_path: PurePath, element: IliasPageElement) -> None:
element_path = PurePath(parent_path, element.name) element_path = PurePath(parent_path, element.name)
@ -208,11 +257,12 @@ class KitIliasWebCrawler(HttpCrawler):
if not dl: if not dl:
return return
@_iorepeat(3, "link resolving")
async def impl() -> None:
assert dl # This function is only reached when dl is not None
async with dl as (bar, sink): async with dl as (bar, sink):
export_url = element.url.replace("cmd=calldirectlink", "cmd=exportHTML") export_url = element.url.replace("cmd=calldirectlink", "cmd=exportHTML")
async with self.session.get(export_url) as response: real_url = await self._resolve_link_target(export_url)
html_page: BeautifulSoup = soupify(await response.read())
real_url: str = html_page.select_one("a").get("href").strip()
content = link_template_plain if self._link_file_use_plaintext else link_template_rich content = link_template_plain if self._link_file_use_plaintext else link_template_rich
content = content.replace("{{link}}", real_url) content = content.replace("{{link}}", real_url)
@ -222,26 +272,53 @@ class KitIliasWebCrawler(HttpCrawler):
sink.file.write(content.encode("utf-8")) sink.file.write(content.encode("utf-8"))
sink.done() sink.done()
await impl()
async def _resolve_link_target(self, export_url: str) -> str:
async with self.session.get(export_url, allow_redirects=False) as resp:
# No redirect means we were authenticated
if hdrs.LOCATION not in resp.headers:
return soupify(await resp.read()).select_one("a").get("href").strip()
self._authenticate()
async with self.session.get(export_url, allow_redirects=False) as resp:
# No redirect means we were authenticated
if hdrs.LOCATION not in resp.headers:
return soupify(await resp.read()).select_one("a").get("href").strip()
raise CrawlError("resolve_link_target failed even after authenticating")
async def _download_video(self, element: IliasPageElement, element_path: PurePath) -> None: async def _download_video(self, element: IliasPageElement, element_path: PurePath) -> None:
# Videos will NOT be redownloaded - their content doesn't really change and they are chunky # Videos will NOT be redownloaded - their content doesn't really change and they are chunky
dl = await self.download(element_path, mtime=element.mtime, redownload=Redownload.NEVER) dl = await self.download(element_path, mtime=element.mtime, redownload=Redownload.NEVER)
if not dl: if not dl:
return return
@_iorepeat(3, "video download")
async def impl() -> None:
assert dl # The function is only reached when dl is not None
async with dl as (bar, sink): async with dl as (bar, sink):
page = IliasPage(await self._get_page(element.url), element.url, element) page = IliasPage(await self._get_page(element.url), element.url, element)
real_element = page.get_child_elements()[0] real_element = page.get_child_elements()[0]
await self._stream_from_url(real_element.url, sink, bar) await self._stream_from_url(real_element.url, sink, bar)
await impl()
async def _download_file(self, element: IliasPageElement, element_path: PurePath) -> None: async def _download_file(self, element: IliasPageElement, element_path: PurePath) -> None:
dl = await self.download(element_path, mtime=element.mtime) dl = await self.download(element_path, mtime=element.mtime)
if not dl: if not dl:
return return
@_iorepeat(3, "file download")
async def impl() -> None:
assert dl # The function is only reached when dl is not None
async with dl as (bar, sink): async with dl as (bar, sink):
await self._stream_from_url(element.url, sink, bar) await self._stream_from_url(element.url, sink, bar)
await impl()
async def _stream_from_url(self, url: str, sink: FileSink, bar: ProgressBar) -> None: async def _stream_from_url(self, url: str, sink: FileSink, bar: ProgressBar) -> None:
async def try_stream() -> bool: async def try_stream() -> bool:
async with self.session.get(url, allow_redirects=False) as resp: async with self.session.get(url, allow_redirects=False) as resp: