107 lines
3.8 KiB
Python
107 lines
3.8 KiB
Python
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"""HTTP cache implementation.
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"""
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import os
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from contextlib import contextmanager
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from datetime import datetime
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from typing import BinaryIO, Generator, Optional, Union
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from pip._vendor.cachecontrol.cache import SeparateBodyBaseCache
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from pip._vendor.cachecontrol.caches import SeparateBodyFileCache
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from pip._vendor.requests.models import Response
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from pip._internal.utils.filesystem import adjacent_tmp_file, replace
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from pip._internal.utils.misc import ensure_dir
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def is_from_cache(response: Response) -> bool:
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return getattr(response, "from_cache", False)
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@contextmanager
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def suppressed_cache_errors() -> Generator[None, None, None]:
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"""If we can't access the cache then we can just skip caching and process
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requests as if caching wasn't enabled.
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"""
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try:
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yield
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except OSError:
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pass
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class SafeFileCache(SeparateBodyBaseCache):
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"""
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A file based cache which is safe to use even when the target directory may
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not be accessible or writable.
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There is a race condition when two processes try to write and/or read the
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same entry at the same time, since each entry consists of two separate
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files (https://github.com/psf/cachecontrol/issues/324). We therefore have
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additional logic that makes sure that both files to be present before
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returning an entry; this fixes the read side of the race condition.
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For the write side, we assume that the server will only ever return the
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same data for the same URL, which ought to be the case for files pip is
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downloading. PyPI does not have a mechanism to swap out a wheel for
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another wheel, for example. If this assumption is not true, the
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CacheControl issue will need to be fixed.
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"""
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def __init__(self, directory: str) -> None:
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assert directory is not None, "Cache directory must not be None."
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super().__init__()
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self.directory = directory
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def _get_cache_path(self, name: str) -> str:
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# From cachecontrol.caches.file_cache.FileCache._fn, brought into our
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# class for backwards-compatibility and to avoid using a non-public
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# method.
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hashed = SeparateBodyFileCache.encode(name)
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parts = list(hashed[:5]) + [hashed]
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return os.path.join(self.directory, *parts)
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def get(self, key: str) -> Optional[bytes]:
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# The cache entry is only valid if both metadata and body exist.
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metadata_path = self._get_cache_path(key)
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body_path = metadata_path + ".body"
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if not (os.path.exists(metadata_path) and os.path.exists(body_path)):
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return None
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with suppressed_cache_errors():
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with open(metadata_path, "rb") as f:
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return f.read()
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def _write(self, path: str, data: bytes) -> None:
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with suppressed_cache_errors():
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ensure_dir(os.path.dirname(path))
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with adjacent_tmp_file(path) as f:
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f.write(data)
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replace(f.name, path)
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def set(
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self, key: str, value: bytes, expires: Union[int, datetime, None] = None
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) -> None:
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path = self._get_cache_path(key)
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self._write(path, value)
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def delete(self, key: str) -> None:
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path = self._get_cache_path(key)
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with suppressed_cache_errors():
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os.remove(path)
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with suppressed_cache_errors():
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os.remove(path + ".body")
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def get_body(self, key: str) -> Optional[BinaryIO]:
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# The cache entry is only valid if both metadata and body exist.
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metadata_path = self._get_cache_path(key)
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body_path = metadata_path + ".body"
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if not (os.path.exists(metadata_path) and os.path.exists(body_path)):
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return None
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with suppressed_cache_errors():
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return open(body_path, "rb")
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def set_body(self, key: str, body: bytes) -> None:
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path = self._get_cache_path(key) + ".body"
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self._write(path, body)
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