diff --git a/docs/topics/downloader-middleware.rst b/docs/topics/downloader-middleware.rst index 934eb19ac..fcfe7fd29 100644 --- a/docs/topics/downloader-middleware.rst +++ b/docs/topics/downloader-middleware.rst @@ -564,6 +564,10 @@ defines the methods described below. Return response if present in cache, or ``None`` otherwise. + If this method raises an exception, e.g. because the cache entry is + corrupted, the middleware logs a warning and handles the request as a + cache miss. + :param spider: the spider which generated the request :type spider: :class:`~scrapy.Spider` object diff --git a/scrapy/downloadermiddlewares/httpcache.py b/scrapy/downloadermiddlewares/httpcache.py index c6c811809..e7ca0ac0e 100644 --- a/scrapy/downloadermiddlewares/httpcache.py +++ b/scrapy/downloadermiddlewares/httpcache.py @@ -1,5 +1,6 @@ from __future__ import annotations +import logging from email.utils import formatdate from typing import TYPE_CHECKING @@ -28,6 +29,9 @@ if TYPE_CHECKING: from scrapy.statscollectors import StatsCollector +logger = logging.getLogger(__name__) + + class HttpCacheMiddleware: DOWNLOAD_EXCEPTIONS = ( ConnectionDone, @@ -77,9 +81,20 @@ class HttpCacheMiddleware: return None # Look for cached response and check if expired - cachedresponse: Response | None = self.storage.retrieve_response( - self.crawler.spider, request - ) + cachedresponse: Response | None + try: + cachedresponse = self.storage.retrieve_response( + self.crawler.spider, request + ) + except Exception: + self.stats.inc_value("httpcache/retrieve_error") + logger.warning( + f"Could not read the cache entry for {request}, treating it as a " + f"cache miss.", + exc_info=True, + extra={"spider": self.crawler.spider}, + ) + cachedresponse = None if cachedresponse is None: self.stats.inc_value("httpcache/miss") if self.ignore_missing: diff --git a/tests/test_downloadermiddleware_httpcache.py b/tests/test_downloadermiddleware_httpcache.py index 9d5d6874e..ce56ee11d 100644 --- a/tests/test_downloadermiddleware_httpcache.py +++ b/tests/test_downloadermiddleware_httpcache.py @@ -1,10 +1,12 @@ from __future__ import annotations import email.utils +import logging import shutil import tempfile import time from contextlib import contextmanager +from pathlib import Path from typing import TYPE_CHECKING, Any from unittest import mock @@ -93,6 +95,12 @@ class TestBase: class StorageTestMixin: """Mixin containing storage-specific test methods.""" + def _corrupt_cache_entry( + self, storage: Any, spider: Spider, request: Request + ) -> None: + """Make the cache entry of *request* unreadable for *storage*.""" + raise NotImplementedError + def test_storage(self): with self._storage(HTTPCACHE_EXPIRATION_SECS=1) as (storage, crawler): request2 = self.request.copy() @@ -115,6 +123,38 @@ class StorageTestMixin: with mock.patch("scrapy.extensions.httpcache.time", return_value=future): assert storage.retrieve_response(crawler.spider, self.request) + def test_corrupted_cache_entry_is_a_miss(self, caplog): + with self._middleware() as mw: + spider = mw.crawler.spider + mw.storage.store_response(spider, self.request, self.response) + self._corrupt_cache_entry(mw.storage, spider, self.request) + + caplog.clear() + with caplog.at_level(logging.WARNING): + assert mw.process_request(self.request) is None + + assert "treating it as a cache miss" in caplog.text + assert mw.crawler.stats.get_value("httpcache/retrieve_error") == 1 + assert mw.crawler.stats.get_value("httpcache/miss") == 1 + + # Storing the response again replaces the corrupted cache entry. + mw.storage.store_response(spider, self.request, self.response) + self.assertEqualResponse( + self.response, mw.storage.retrieve_response(spider, self.request) + ) + + def test_corrupted_cache_entry_ignore_missing(self): + with self._middleware(HTTPCACHE_IGNORE_MISSING=True) as mw: + spider = mw.crawler.spider + mw.storage.store_response(spider, self.request, self.response) + self._corrupt_cache_entry(mw.storage, spider, self.request) + + with pytest.raises(IgnoreRequest): + mw.process_request(self.request) + + assert mw.crawler.stats.get_value("httpcache/retrieve_error") == 1 + assert mw.crawler.stats.get_value("httpcache/ignore") == 1 + def test_storage_no_content_type_header(self): """Test that the response body is used to get the right response class even if there is no Content-Type header""" @@ -556,29 +596,43 @@ class RFC2616PolicyTestMixin(PolicyTestMixin): # Concrete test classes that combine storage and policy mixins -class TestFilesystemStorageWithDummyPolicy( - TestBase, StorageTestMixin, DummyPolicyTestMixin -): +class FilesystemStorageTestMixin(StorageTestMixin): storage_class = "scrapy.extensions.httpcache.FilesystemCacheStorage" + + def _corrupt_cache_entry(self, storage, spider, request) -> None: + rpath = Path(storage._get_request_path(spider, request)) + (rpath / "response_body").unlink() + + +class DbmStorageTestMixin(StorageTestMixin): + storage_class = "scrapy.extensions.httpcache.DbmCacheStorage" + + def _corrupt_cache_entry(self, storage, spider, request) -> None: + key = storage._fingerprinter.fingerprint(request).hex() + storage.db[f"{key}_data"] = b"not a pickle" + + +class TestFilesystemStorageWithDummyPolicy( + TestBase, FilesystemStorageTestMixin, DummyPolicyTestMixin +): policy_class = "scrapy.extensions.httpcache.DummyPolicy" class TestFilesystemStorageWithRFC2616Policy( - TestBase, StorageTestMixin, RFC2616PolicyTestMixin + TestBase, FilesystemStorageTestMixin, RFC2616PolicyTestMixin ): - storage_class = "scrapy.extensions.httpcache.FilesystemCacheStorage" policy_class = "scrapy.extensions.httpcache.RFC2616Policy" -class TestDbmStorageWithDummyPolicy(TestBase, StorageTestMixin, DummyPolicyTestMixin): - storage_class = "scrapy.extensions.httpcache.DbmCacheStorage" +class TestDbmStorageWithDummyPolicy( + TestBase, DbmStorageTestMixin, DummyPolicyTestMixin +): policy_class = "scrapy.extensions.httpcache.DummyPolicy" class TestDbmStorageWithRFC2616Policy( - TestBase, StorageTestMixin, RFC2616PolicyTestMixin + TestBase, DbmStorageTestMixin, RFC2616PolicyTestMixin ): - storage_class = "scrapy.extensions.httpcache.DbmCacheStorage" policy_class = "scrapy.extensions.httpcache.RFC2616Policy" @@ -599,3 +653,8 @@ class TestFilesystemStorageGzipWithDummyPolicy(TestFilesystemStorageWithDummyPol def _get_settings(self, **new_settings) -> dict[str, Any]: new_settings.setdefault("HTTPCACHE_GZIP", True) return super()._get_settings(**new_settings) + + def _corrupt_cache_entry(self, storage, spider, request) -> None: + # A spider killed while writing a gzip file leaves it truncated. + body_path = Path(storage._get_request_path(spider, request), "response_body") + body_path.write_bytes(body_path.read_bytes()[:-5])