Edit File: bccache.py
# -*- coding: utf-8 -*- """ jinja2.bccache ~~~~~~~~~~~~~~ This module implements the bytecode cache system Jinja is optionally using. This is useful if you have very complex template situations and the compiliation of all those templates slow down your application too much. Situations where this is useful are often forking web applications that are initialized on the first request. :copyright: (c) 2010 by the Jinja Team. :license: BSD. """ from os import path, listdir import os import stat import sys import errno import marshal import tempfile import fnmatch from hashlib import sha1 from jinja2.utils import open_if_exists from jinja2._compat import BytesIO, pickle, PY2, text_type # marshal works better on 3.x, one hack less required if not PY2: marshal_dump = marshal.dump marshal_load = marshal.load else: def marshal_dump(code, f): if isinstance(f, file): marshal.dump(code, f) else: f.write(marshal.dumps(code)) def marshal_load(f): if isinstance(f, file): return marshal.load(f) return marshal.loads(f.read()) bc_version = 2 # magic version used to only change with new jinja versions. With 2.6 # we change this to also take Python version changes into account. The # reason for this is that Python tends to segfault if fed earlier bytecode # versions because someone thought it would be a good idea to reuse opcodes # or make Python incompatible with earlier versions. bc_magic = 'j2'.encode('ascii') + \ pickle.dumps(bc_version, 2) + \ pickle.dumps((sys.version_info[0] << 24) | sys.version_info[1]) class Bucket(object): """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 The buckets get an internal checksum from the cache assigned and use this to automatically reject outdated cache material.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, key, checksum): self.environment = environment self.key = key self.checksum = checksum self.reset() def reset(self): """Resets the bucket (unloads the bytecode).""" self.code = None def load_bytecode(self, f): """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 self.code = marshal_load(f) def write_bytecode(self, f): """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): """Load bytecode from a string.""" self.load_bytecode(BytesIO(string)) def bytecode_to_string(self): """Return the bytecode as string.""" out = BytesIO() self.write_bytecode(out) return out.getvalue() class BytecodeCache(object): """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 Jinja2. """ def load_bytecode(self, bucket): """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): """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): """Clears the cache. This method is not used by Jinja2 but should be implemented to allow applications to clear the bytecode cache used by a particular environment. """ def get_cache_key(self, name, filename=None): """Returns the unique hash key for this template name.""" hash = sha1(name.encode('utf-8')) if filename is not None: filename = '|' + filename if isinstance(filename, text_type): filename = filename.encode('utf-8') hash.update(filename) return hash.hexdigest() def get_source_checksum(self, source): """Returns a checksum for the source.""" return sha1(source.encode('utf-8')).hexdigest() def get_bucket(self, environment, name, filename, source): """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): """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=None, pattern='__jinja2_%s.cache'): if directory is None: directory = self._get_default_cache_dir() self.directory = directory self.pattern = pattern def _get_default_cache_dir(self): tmpdir = tempfile.gettempdir() # On windows the temporary directory is used specific unless # explicitly forced otherwise. We can just use that. if os.name == 'n': return tmpdir if not hasattr(os, 'getuid'): raise RuntimeError('Cannot determine safe temp directory. You ' 'need to explicitly provide one.') dirname = '_jinja2-cache-%d' % os.getuid() actual_dir = os.path.join(tmpdir, dirname) try: # 448 == 0700 os.mkdir(actual_dir, 448) except OSError as e: if e.errno != errno.EEXIST: raise if os.lstat(actual_dir).st_uid != os.getuid(): raise RuntimeError('Someone else owns temp directory with your ' 'uid. You need to explicitly provide another.') if stat.S_IMODE(os.lstat(actual_dir).st_mode) != 448: raise RuntimeError('Bad permission flags on temp directory, ' 'shoud be 0700. You need to fix this.') return actual_dir def _get_cache_filename(self, bucket): return path.join(self.directory, self.pattern % bucket.key) def load_bytecode(self, bucket): f = open_if_exists(self._get_cache_filename(bucket), 'rb') if f is not None: try: bucket.load_bytecode(f) finally: f.close() def dump_bytecode(self, bucket): f = open(self._get_cache_filename(bucket), 'wb') try: bucket.write_bytecode(f) finally: f.close() def clear(self): # 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(listdir(self.directory), self.pattern % '*') for filename in files: try: remove(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: - `werkzeug <http://werkzeug.pocoo.org/>`_.contrib.cache - `python-memcached <http://www.tummy.com/Community/software/python-memcached/>`_ - `cmemcache <http://gijsbert.org/cmemcache/>`_ (Unfortunately the django cache interface is not compatible because it does not support storing binary data, only unicode. 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, prefix='jinja2/bytecode/', timeout=None, ignore_memcache_errors=True): self.client = client self.prefix = prefix self.timeout = timeout self.ignore_memcache_errors = ignore_memcache_errors def load_bytecode(self, bucket): try: code = self.client.get(self.prefix + bucket.key) except Exception: if not self.ignore_memcache_errors: raise code = None if code is not None: bucket.bytecode_from_string(code) def dump_bytecode(self, bucket): args = (self.prefix + bucket.key, bucket.bytecode_to_string()) if self.timeout is not None: args += (self.timeout,) try: self.client.set(*args) except Exception: if not self.ignore_memcache_errors: raise