133 lines
5.2 KiB
Python
133 lines
5.2 KiB
Python
"""HTTP cache implementation."""
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from __future__ import annotations
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import os
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import shutil
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from collections.abc import Generator
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from contextlib import contextmanager
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from datetime import datetime
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from typing import Any, BinaryIO, Callable
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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) -> bytes | None:
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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_to_file(self, path: str, writer_func: Callable[[BinaryIO], Any]) -> None:
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"""Common file writing logic with proper permissions and atomic replacement."""
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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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writer_func(f)
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# Inherit the read/write permissions of the cache directory
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# to enable multi-user cache use-cases.
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mode = (
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os.stat(self.directory).st_mode
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& 0o666 # select read/write permissions of cache directory
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| 0o600 # set owner read/write permissions
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)
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# Change permissions only if there is no risk of following a symlink.
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if os.chmod in os.supports_fd:
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os.chmod(f.fileno(), mode)
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elif os.chmod in os.supports_follow_symlinks:
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os.chmod(f.name, mode, follow_symlinks=False)
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replace(f.name, path)
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def _write(self, path: str, data: bytes) -> None:
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self._write_to_file(path, lambda f: f.write(data))
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def _write_from_io(self, path: str, source_file: BinaryIO) -> None:
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self._write_to_file(path, lambda f: shutil.copyfileobj(source_file, f))
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def set(
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self, key: str, value: bytes, expires: 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) -> BinaryIO | None:
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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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def set_body_from_io(self, key: str, body_file: BinaryIO) -> None:
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"""Set the body of the cache entry from a file object."""
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path = self._get_cache_path(key) + ".body"
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self._write_from_io(path, body_file)
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