diff options
Diffstat (limited to 'src/jinja2/bccache.py')
| -rw-r--r-- | src/jinja2/bccache.py | 353 |
1 files changed, 353 insertions, 0 deletions
diff --git a/src/jinja2/bccache.py b/src/jinja2/bccache.py new file mode 100644 index 00000000..6f897451 --- /dev/null +++ b/src/jinja2/bccache.py @@ -0,0 +1,353 @@ +# -*- coding: utf-8 -*- +"""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 os +import stat +import sys +import tempfile +from hashlib import sha1 +from os import listdir +from os import path + +from ._compat import BytesIO +from ._compat import marshal_dump +from ._compat import marshal_load +from ._compat import pickle +from ._compat import text_type +from .utils import open_if_exists + +bc_version = 3 + +# 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 + + The buckets get an internal checksum from the cache assigned and use this + to automatically reject outdated cache material.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 + # 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): + """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 + Jinja. + """ + + 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 Jinja 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): + def _unsafe_dir(): + 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 = "_jinja2-cache-%d" % 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): + 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: + + - `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 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 |