Mercurial > libervia-backend
view sat/memory/cache.py @ 3377:297389b1563c
jp (application/list): don't use `extend` in argument as in it Python 3.8+ only
author | Goffi <goffi@goffi.org> |
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date | Thu, 01 Oct 2020 10:12:01 +0200 |
parents | fedec192a83f |
children | be6d91572633 |
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#!/usr/bin/env python3 # SAT: a jabber client # Copyright (C) 2009-2020 Jérôme Poisson (goffi@goffi.org) # This program is free software: you can redistribute it and/or modify # it under the terms of the GNU Affero General Public License as published by # the Free Software Foundation, either version 3 of the License, or # (at your option) any later version. # This program is distributed in the hope that it will be useful, # but WITHOUT ANY WARRANTY; without even the implied warranty of # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the # GNU Affero General Public License for more details. # You should have received a copy of the GNU Affero General Public License # along with this program. If not, see <http://www.gnu.org/licenses/>. import pickle as pickle import mimetypes import time from pathlib import Path from sat.core.i18n import _ from sat.core.log import getLogger from sat.core.constants import Const as C from sat.core import exceptions from sat.tools.common import regex log = getLogger(__name__) DEFAULT_EXT = ".raw" class Cache(object): """generic file caching""" def __init__(self, host, profile): """ @param profile(unicode, None): ame of the profile to set the cache for if None, the cache will be common for all profiles """ self.profile = profile path_elts = [host.memory.getConfig("", "local_dir"), C.CACHE_DIR] if profile: path_elts.extend(["profiles", regex.pathEscape(profile)]) else: path_elts.append("common") self.cache_dir = Path(*path_elts) self.cache_dir.mkdir(0o700, parents=True, exist_ok=True) self.purge() def purge(self): # remove expired files from cache # TODO: this should not be called only on startup, but at regular interval # (e.g. once a day) purged = set() # we sort files to have metadata files first for cache_file in sorted(self.cache_dir.iterdir()): if cache_file in purged: continue try: with cache_file.open('rb') as f: cache_data = pickle.load(f) except IOError: log.warning( _("Can't read metadata file at {path}") .format(path=cache_file)) continue except (pickle.UnpicklingError, EOFError): log.debug(f"File at {cache_file} is not a metadata file") continue try: eol = cache_data['eol'] filename = cache_data['filename'] except KeyError: log.warning( _("Invalid cache metadata at {path}") .format(path=cache_file)) continue filepath = self.getPath(filename) if not filepath.exists(): log.warning(_( "cache {cache_file!r} references an inexisting file: {filepath!r}" ).format(cache_file=str(cache_file), filepath=str(filepath))) log.debug("purging cache with missing file") cache_file.unlink() elif eol < time.time(): log.debug( "purging expired cache {filepath!r} (expired for {time}s)" .format(filepath=str(filepath), time=int(time.time() - eol)) ) cache_file.unlink() try: filepath.unlink() except FileNotFoundError: log.warning( _("following file is missing while purging cache: {path}") .format(path=filepath) ) purged.add(cache_file) purged.add(filepath) def getPath(self, filename): """return cached file URL @param filename(str): cached file name (cache data or actual file) @return (Path): path to the cached file """ if not filename or "/" in filename: log.error( "invalid char found in file name, hack attempt? name:{}".format(filename) ) raise exceptions.DataError("Invalid char found") return self.cache_dir / filename def getMetadata(self, uid, update_eol=True): """Retrieve metadata for cached data @param uid(unicode): unique identifier of file @param update_eol(bool): True if eol must extended if True, max_age will be added to eol (only if it is not already expired) @return (dict, None): metadata with following keys: see [cacheData] for data details, an additional "path" key is the full path to cached file. None if file is not in cache (or cache is invalid) """ uid = uid.strip() if not uid: raise exceptions.InternalError("uid must not be empty") cache_url = self.getPath(uid) if not cache_url.exists(): return None try: with cache_url.open("rb") as f: cache_data = pickle.load(f) except IOError as e: log.warning(f"can't read cache at {cache_url}: {e}") return None except pickle.UnpicklingError: log.warning(f"invalid cache found at {cache_url}") return None try: eol = cache_data["eol"] except KeyError: log.warning("no End Of Life found for cached file {}".format(uid)) eol = 0 if eol < time.time(): log.debug( "removing expired cache (expired for {}s)".format(time.time() - eol) ) return None if update_eol: try: max_age = cache_data["max_age"] except KeyError: log.warning(f"no max_age found for cache at {cache_url}, using default") max_age = cache_data["max_age"] = C.DEFAULT_MAX_AGE now = int(time.time()) cache_data["last_access"] = now cache_data["eol"] = now + max_age with cache_url.open("wb") as f: pickle.dump(cache_data, f, protocol=2) cache_data["path"] = self.getPath(cache_data["filename"]) return cache_data def getFilePath(self, uid): """Retrieve absolute path to file @param uid(unicode): unique identifier of file @return (unicode, None): absolute path to cached file None if file is not in cache (or cache is invalid) """ metadata = self.getMetadata(uid) if metadata is not None: return metadata["path"] def removeFromCache(self, uid, metadata=None): """Remove data from cache @param uid(unicode): unique identifier cache file """ cache_data = self.getMetadata(uid, update_eol=False) if cache_data is None: log.debug(f"cache with uid {uid!r} has already expired or been removed") return try: filename = cache_data['filename'] except KeyError: log.warning(_("missing filename for cache {uid!r}") .format(uid=uid)) else: filepath = self.getPath(filename) try: filepath.unlink() except FileNotFoundError: log.warning( _("missing file referenced in cache {uid!r}: {filename}") .format(uid=uid, filename=filename) ) cache_file = self.getPath(uid) cache_file.unlink() log.debug(f"cache with uid {uid!r} has been removed") def cacheData(self, source, uid, mime_type=None, max_age=None, filename=None): """create cache metadata and file object to use for actual data @param source(unicode): source of the cache (should be plugin's import_name) @param uid(unicode): an identifier of the file which must be unique @param mime_type(unicode): MIME type of the file to cache it will be used notably to guess file extension It may be autogenerated if filename is specified @param max_age(int, None): maximum age in seconds the cache metadata will have an "eol" (end of life) None to use default value 0 to ignore cache (file will be re-downloaded on each access) @param filename: if not None, will be used as filename else one will be generated from uid and guessed extension @return(file): file object opened in write mode you have to close it yourself (hint: use with statement) """ cache_url = self.getPath(uid) if filename is None: if mime_type: ext = mimetypes.guess_extension(mime_type, strict=False) if ext is None: log.warning( "can't find extension for MIME type {}".format(mime_type) ) ext = DEFAULT_EXT elif ext == ".jpe": ext = ".jpg" else: ext = DEFAULT_EXT mime_type = None filename = uid + ext elif mime_type is None: # we have filename but not MIME type, we try to guess the later mime_type = mimetypes.guess_type(filename, strict=False)[0] if max_age is None: max_age = C.DEFAULT_MAX_AGE now = int(time.time()) cache_data = { "source": source, "filename": filename, "creation": now, "eol": now + max_age, # we also store max_age for updating eol "max_age": max_age, "mime_type": mime_type, } file_path = self.getPath(filename) with open(cache_url, "wb") as f: pickle.dump(cache_data, f, protocol=2) return file_path.open("wb")