JezK
Edit File: bccache.py
"""The optional bytecode cache system. This is useful if you have very complex template situations and the compilation of all those templates slows down your application too much. Situations where this is useful are often forking web applications that are initialized on the first request. """ import errno import fnmatch import marshal import os import pickle import stat import sys import tempfile import typing as t from hashlib import sha1 from io import BytesIO from types import CodeType if t.TYPE_CHECKING: import typing_extensions as te from .environment import Environment class _MemcachedClient(te.Protocol): def get(self, key: str) -> bytes: ... def set(self, key: str, value: bytes, timeout: t.Optional[int] = None) -> None: ... bc_version = 5 # Magic bytes to identify Jinja bytecode cache files. Contains the # Python major and minor version to avoid loading incompatible bytecode # if a project upgrades its Python version. bc_magic = ( b"j2" + pickle.dumps(bc_version, 2) + pickle.dumps((sys.version_info[0] << 24) | sys.version_info[1], 2) ) class Bucket: """Buckets are used to store the bytecode for one template. It's created and initialized by the bytecode cache and passed to the loading functions. The buckets get an internal checksum from the cache assigned and use this to automatically reject outdated cache material. Individual bytecode cache subclasses don't have to care about cache invalidation. """ def __init__(self, environment: "Environment", key: str, checksum: str) -> None: self.environment = environment self.key = key self.checksum = checksum self.reset() def reset(self) -> None: """Resets the bucket (unloads the bytecode).""" self.code: t.Optional[CodeType] = None def load_bytecode(self, f: t.BinaryIO) -> None: """Loads bytecode from a file or file like object.""" # make sure the magic header is correct magic = f.read(len(bc_magic)) if magic != bc_magic: self.reset() return # the source code of the file changed, we need to reload checksum = pickle.load(f) if self.checksum != checksum: self.reset() return # if marshal_load fails then we need to reload try: self.code = marshal.load(f) except (EOFError, ValueError, TypeError): self.reset() return def write_bytecode(self, f: t.IO[bytes]) -> None: """Dump the bytecode into the file or file like object passed.""" if self.code is None: raise TypeError("can't write empty bucket") f.write(bc_magic) pickle.dump(self.checksum, f, 2) marshal.dump(self.code, f) def bytecode_from_string(self, string: bytes) -> None: """Load bytecode from bytes.""" self.load_bytecode(BytesIO(string)) def bytecode_to_string(self) -> bytes: """Return the bytecode as bytes.""" out = BytesIO() self.write_bytecode(out) return out.getvalue() class BytecodeCache: """To implement your own bytecode cache you have to subclass this class and override :meth:`load_bytecode` and :meth:`dump_bytecode`. Both of these methods are passed a :class:`~jinja2.bccache.Bucket`. A very basic bytecode cache that saves the bytecode on the file system:: from os import path class MyCache(BytecodeCache): def __init__(self, directory): self.directory = directory def load_bytecode(self, bucket): filename = path.join(self.directory, bucket.key) if path.exists(filename): with open(filename, 'rb') as f: bucket.load_bytecode(f) def dump_bytecode(self, bucket): filename = path.join(self.directory, bucket.key) with open(filename, 'wb') as f: bucket.write_bytecode(f) A more advanced version of a filesystem based bytecode cache is part of Jinja. """ def load_bytecode(self, bucket: Bucket) -> None: """Subclasses have to override this method to load bytecode into a bucket. If they are not able to find code in the cache for the bucket, it must not do anything. """ raise NotImplementedError() def dump_bytecode(self, bucket: Bucket) -> None: """Subclasses have to override this method to write the bytecode from a bucket back to the cache. If it unable to do so it must not fail silently but raise an exception. """ raise NotImplementedError() def clear(self) -> None: """Clears the cache. This method is not used by Jinja but should be implemented to allow applications to clear the bytecode cache used by a particular environment. """ def get_cache_key( self, name: str, filename: t.Optional[t.Union[str]] = None ) -> str: """Returns the unique hash key for this template name.""" hash = sha1(name.encode("utf-8")) if filename is not None: hash.update(f"|{filename}".encode()) return hash.hexdigest() def get_source_checksum(self, source: str) -> str: """Returns a checksum for the source.""" return sha1(source.encode("utf-8")).hexdigest() def get_bucket( self, environment: "Environment", name: str, filename: t.Optional[str], source: str, ) -> Bucket: """Return a cache bucket for the given template. All arguments are mandatory but filename may be `None`. """ key = self.get_cache_key(name, filename) checksum = self.get_source_checksum(source) bucket = Bucket(environment, key, checksum) self.load_bytecode(bucket) return bucket def set_bucket(self, bucket: Bucket) -> None: """Put the bucket into the cache.""" self.dump_bytecode(bucket) class FileSystemBytecodeCache(BytecodeCache): """A bytecode cache that stores bytecode on the filesystem. It accepts two arguments: The directory where the cache items are stored and a pattern string that is used to build the filename. If no directory is specified a default cache directory is selected. On Windows the user's temp directory is used, on UNIX systems a directory is created for the user in the system temp directory. The pattern can be used to have multiple separate caches operate on the same directory. The default pattern is ``'__jinja2_%s.cache'``. ``%s`` is replaced with the cache key. >>> bcc = FileSystemBytecodeCache('/tmp/jinja_cache', '%s.cache') This bytecode cache supports clearing of the cache using the clear method. """ def __init__( self, directory: t.Optional[str] = None, pattern: str = "__jinja2_%s.cache" ) -> None: if directory is None: directory = self._get_default_cache_dir() self.directory = directory self.pattern = pattern def _get_default_cache_dir(self) -> str: def _unsafe_dir() -> "te.NoReturn": raise RuntimeError( "Cannot determine safe temp directory. You " "need to explicitly provide one." ) tmpdir = tempfile.gettempdir() # On windows the temporary directory is used specific unless # explicitly forced otherwise. We can just use that. if os.name == "nt": return tmpdir if not hasattr(os, "getuid"): _unsafe_dir() dirname = f"_jinja2-cache-{os.getuid()}" actual_dir = os.path.join(tmpdir, dirname) try: os.mkdir(actual_dir, stat.S_IRWXU) except OSError as e: if e.errno != errno.EEXIST: raise try: os.chmod(actual_dir, stat.S_IRWXU) actual_dir_stat = os.lstat(actual_dir) if ( actual_dir_stat.st_uid != os.getuid() or not stat.S_ISDIR(actual_dir_stat.st_mode) or stat.S_IMODE(actual_dir_stat.st_mode) != stat.S_IRWXU ): _unsafe_dir() except OSError as e: if e.errno != errno.EEXIST: raise actual_dir_stat = os.lstat(actual_dir) if ( actual_dir_stat.st_uid != os.getuid() or not stat.S_ISDIR(actual_dir_stat.st_mode) or stat.S_IMODE(actual_dir_stat.st_mode) != stat.S_IRWXU ): _unsafe_dir() return actual_dir def _get_cache_filename(self, bucket: Bucket) -> str: return os.path.join(self.directory, self.pattern % (bucket.key,)) def load_bytecode(self, bucket: Bucket) -> None: filename = self._get_cache_filename(bucket) # Don't test for existence before opening the file, since the # file could disappear after the test before the open. try: f = open(filename, "rb") except (FileNotFoundError, IsADirectoryError, PermissionError): # PermissionError can occur on Windows when an operation is # in progress, such as calling clear(). return with f: bucket.load_bytecode(f) def dump_bytecode(self, bucket: Bucket) -> None: # Write to a temporary file, then rename to the real name after # writing. This avoids another process reading the file before # it is fully written. name = self._get_cache_filename(bucket) f = tempfile.NamedTemporaryFile( mode="wb", dir=os.path.dirname(name), prefix=os.path.basename(name), suffix=".tmp", delete=False, ) def remove_silent() -> None: try: os.remove(f.name) except OSError: # Another process may have called clear(). On Windows, # another program may be holding the file open. pass try: with f: bucket.write_bytecode(f) except BaseException: remove_silent() raise try: os.replace(f.name, name) except OSError: # Another process may have called clear(). On Windows, # another program may be holding the file open. remove_silent() except BaseException: remove_silent() raise def clear(self) -> None: # imported lazily here because google app-engine doesn't support # write access on the file system and the function does not exist # normally. from os import remove files = fnmatch.filter(os.listdir(self.directory), self.pattern % ("*",)) for filename in files: try: remove(os.path.join(self.directory, filename)) except OSError: pass class MemcachedBytecodeCache(BytecodeCache): """This class implements a bytecode cache that uses a memcache cache for storing the information. It does not enforce a specific memcache library (tummy's memcache or cmemcache) but will accept any class that provides the minimal interface required. Libraries compatible with this class: - `cachelib <https://github.com/pallets/cachelib>`_ - `python-memcached <https://pypi.org/project/python-memcached/>`_ (Unfortunately the django cache interface is not compatible because it does not support storing binary data, only text. You can however pass the underlying cache client to the bytecode cache which is available as `django.core.cache.cache._client`.) The minimal interface for the client passed to the constructor is this: .. class:: MinimalClientInterface .. method:: set(key, value[, timeout]) Stores the bytecode in the cache. `value` is a string and `timeout` the timeout of the key. If timeout is not provided a default timeout or no timeout should be assumed, if it's provided it's an integer with the number of seconds the cache item should exist. .. method:: get(key) Returns the value for the cache key. If the item does not exist in the cache the return value must be `None`. The other arguments to the constructor are the prefix for all keys that is added before the actual cache key and the timeout for the bytecode in the cache system. We recommend a high (or no) timeout. This bytecode cache does not support clearing of used items in the cache. The clear method is a no-operation function. .. versionadded:: 2.7 Added support for ignoring memcache errors through the `ignore_memcache_errors` parameter. """ def __init__( self, client: "_MemcachedClient", prefix: str = "jinja2/bytecode/", timeout: t.Optional[int] = None, ignore_memcache_errors: bool = True, ): self.client = client self.prefix = prefix self.timeout = timeout self.ignore_memcache_errors = ignore_memcache_errors def load_bytecode(self, bucket: Bucket) -> None: try: code = self.client.get(self.prefix + bucket.key) except Exception: if not self.ignore_memcache_errors: raise else: bucket.bytecode_from_string(code) def dump_bytecode(self, bucket: Bucket) -> None: key = self.prefix + bucket.key value = bucket.bytecode_to_string() try: if self.timeout is not None: self.client.set(key, value, self.timeout) else: self.client.set(key, value) except Exception: if not self.ignore_memcache_errors: raise