import sqlite3 import threading from contextlib import contextmanager from logging import getLogger from os import makedirs from os.path import abspath, basename, dirname, expanduser, isabs, join from pathlib import Path from tempfile import gettempdir from typing import Type, Union from . import BaseCache, BaseStorage, get_valid_kwargs logger = getLogger(__name__) class DbCache(BaseCache): """SQLite cache backend. Args: db_path: Database file path (expands user paths and creates parent dirs) use_temp: Store database in a temp directory (e.g., ``/tmp/http_cache.sqlite``). Note: if ``db_path`` is an absolute path, this option will be ignored. fast_save: Speedup cache saving up to 50 times but with possibility of data loss. See :py:class:`.DbDict` for more info kwargs: Additional keyword arguments for :py:func:`sqlite3.connect` """ def __init__( self, db_path: Union[Path, str] = 'http_cache', use_temp: bool = False, fast_save: bool = False, **kwargs ): super().__init__(**kwargs) self.responses = DbPickleDict(db_path, table_name='responses', use_temp=use_temp, fast_save=fast_save, **kwargs) self.redirects = DbDict(db_path, table_name='redirects', use_temp=use_temp, **kwargs) def remove_expired_responses(self, *args, **kwargs): """Remove expired responses from the cache, with additional cleanup""" super().remove_expired_responses(*args, **kwargs) self.responses.vacuum() self.redirects.vacuum() class DbDict(BaseStorage): """A dictionary-like interface for SQLite. It's possible to create multiply DbDict instances, which will be stored as separate tables in one database:: d1 = DbDict('test', 'table1') d2 = DbDict('test', 'table2') d3 = DbDict('test', 'table3') All data will be stored in separate tables in the file ``test.sqlite``. Args: db_path: Database file path table_name: Table name fast_save: Use `"PRAGMA synchronous = 0;" `_ to speed up cache saving, but with the potential for data loss timeout: Timeout for acquiring a database lock """ def __init__(self, db_path, table_name='http_cache', fast_save=False, use_temp: bool = False, **kwargs): kwargs.setdefault('suppress_warnings', True) super().__init__(**kwargs) self.connection_kwargs = get_valid_kwargs(sqlite_template, kwargs) self.db_path = _get_db_path(db_path, use_temp) self.fast_save = fast_save self.table_name = table_name self._can_commit = True self._local_context = threading.local() with sqlite3.connect(self.db_path, **self.connection_kwargs) as con: con.execute("create table if not exists `%s` (key PRIMARY KEY, value)" % self.table_name) @contextmanager def connection(self, commit_on_success=False): if not hasattr(self._local_context, "con"): logger.debug(f'Opening connection to {self.db_path}:{self.table_name}') self._local_context.con = sqlite3.connect(self.db_path, **self.connection_kwargs) if self.fast_save: self._local_context.con.execute("PRAGMA synchronous = 0;") yield self._local_context.con if commit_on_success and self._can_commit: self._local_context.con.commit() def __del__(self): if hasattr(self._local_context, "con"): self._local_context.con.close() @contextmanager def bulk_commit(self): """ Context manager used to speedup insertion of big number of records :: >>> d1 = DbDict('test') >>> with d1.bulk_commit(): ... for i in range(1000): ... d1[i] = i * 2 """ self._can_commit = False try: yield if hasattr(self._local_context, "con"): self._local_context.con.commit() finally: self._can_commit = True def __getitem__(self, key): with self.connection() as con: row = con.execute("select value from `%s` where key=?" % self.table_name, (key,)).fetchone() # raise error after the with block, otherwise the connection will be locked if not row: raise KeyError return row[0] def __setitem__(self, key, item): with self.connection(True) as con: con.execute( "insert or replace into `%s` (key,value) values (?,?)" % self.table_name, (key, item), ) def __delitem__(self, key): with self.connection(True) as con: cur = con.execute("delete from `%s` where key=?" % self.table_name, (key,)) if not cur.rowcount: raise KeyError def __iter__(self): with self.connection() as con: for row in con.execute("select key from `%s`" % self.table_name): yield row[0] def __len__(self): with self.connection() as con: return con.execute("select count(key) from `%s`" % self.table_name).fetchone()[0] def clear(self): with self.connection(True) as con: con.execute("drop table if exists `%s`" % self.table_name) con.execute("create table `%s` (key PRIMARY KEY, value)" % self.table_name) con.execute("vacuum") def vacuum(self): with self.connection(True) as con: con.execute("vacuum") class DbPickleDict(DbDict): """Same as :class:`DbDict`, but pickles values before saving""" def __setitem__(self, key, item): super().__setitem__(key, sqlite3.Binary(self.serialize(item))) def __getitem__(self, key): return self.deserialize(super().__getitem__(key)) def _get_db_path(db_path: Union[Path, str], use_temp: bool) -> str: """Get resolved path for database file""" # Save to a temp directory, if specified if use_temp and not isabs(db_path): db_path = join(gettempdir(), db_path) # Expand relative and user paths (~/*), and add file extension if not specified db_path = abspath(expanduser(str(db_path))) if '.' not in basename(db_path): db_path += '.sqlite' # Make sure parent dirs exist makedirs(dirname(db_path), exist_ok=True) return db_path def sqlite_template( timeout: float = 5.0, detect_types: int = 0, isolation_level: str = None, check_same_thread: bool = True, factory: Type = None, cached_statements: int = 100, uri: bool = False, ): """Template function to get an accurate signature for the builtin :py:func:`sqlite3.connect`"""