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quickimport.py
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quickimport.py
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#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# Copyright (c) 2011 by science+computing ag
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library 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
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
#
"""
=============
Quickimport
=============
The module :mod:`quickimport` provides an improved importer for python. If
you ever started a Python application from a lame file server (like
a CIFS server) you know the problem of long startup times. Usually
the long startup time is caused by the enormous number of
:c:func:`stat()` calls required to locate a module. For each directory
on ``sys.path`` (or on the package specific search path) and for each
possible suffix (see function :func:`imp.get_suffixes`) Python
probes the existence of a module or a package using the
C-function call :c:func:`stat()`. If your search path contains several
directories (if you use easy_install, it usually contains many directories),
you end up with several thousands :c:func:`stat()` calls. Most of
these calls fail, because the probed file does not exist.
The basic idea of Quickimport is to avoid those :c:func:`stat()` calls
that will fail for sure, because there is no matching
file in the directory in question. If we assume, that the content of
the directory does not change while our application is running, we can
read the directory content once. A perfect implementation of this concept
requires a patch for python. Fortunately we can use the PEP-302 import
hooks to create a nearly perfect version, that skips directories
not containing any candidate for the wanted module or package.
You only need to invoke the function :func:`install` early enough.
This function installs a PEP-302 importer and optionally
eliminates directories without any Python modules or packages from
``sys.path``.
Another option to speed up lame imports is to store many modules into
a zip-archive. The time required to extract modules from a zip-archive
is usually much lower than the time to locate the modules on the
file system and to read them. Therefore ``sys.path`` already contains
an entry for a zip-archive ``pythonXY.zip``. The function
:func:`buildZip` creates such a zip-archive for you.
.. warning::
Although the author is using the module quickimport in production, it is
more or less untested outside the specific environment it was written for.
.. autofunction:: install
.. autofunction:: uninstall
.. autofunction:: isDirRelevant
.. autofunction:: prepareCache
.. autofunction:: buildZip
.. autofunction:: newQuickimportFinder
.. autoclass:: NullFinder
.. autoclass:: QuickimportFinder
"""
from __future__ import absolute_import
from __future__ import print_function
import sys
from imp import acquire_lock, release_lock, find_module, get_suffixes, NullImporter
import pkgutil
from pkgutil import ImpLoader
import os.path
import re
suffixes = [ os.path.normcase(s[0]) for s in get_suffixes() ]
initfiles = [ os.path.normcase('__init__' + s) for s in suffixes ]
IDENTIFIER_RE = re.compile(os.path.normcase(r'^[a-zA-Z_][a-zA-Z0-9_]*$'))
AUTOCHACHE_KEY = object()
__all__ = []
DEBUG=False
def dbg(*args, **kwargs):
if DEBUG:
kwargs.setdefault('file', sys.stderr)
print(*args, **kwargs)
def buildZip(zipname=None):
"""
Build a zip-archive containing all suitable top-level modules.
This function creates the zip-archive `zipname` and adds
a compiled version of every suitable top-level module to the
archive. A module is suitable, if the module's Python source
code is available and does not reference the __path__ or
__file__ members.
This function uses the python :mod:`logging` system to report
its progress. Set the log level to ``INFO`` or ``DEBUG`` to get
progress information.
You can run this module as a pathon script to invoke this function::
python -m quickimport [zipname]
:param zipname: the name of the archive. If not given, the function
uses the name of the ``pythonXY.zip``-item of ``sys.path``.
:type zipname: str or unicode
"""
import logging
LOGGER = logging.getLogger(__name__)
import collections
import zipfile
uninstall()
if zipname is None:
for item in sys.path:
if (os.path.isabs(item) and
os.path.normcase(os.path.basename(item)) ==
os.path.normcase("python%s%s%szip" % (sys.version_info[0], sys.version_info[1], os.extsep))):
zipname = item
break
else:
raise RuntimeError("Failed to determine zipname from sys.path. Please provide the zipname argument.")
LOGGER.info("Creating zip archive %r ...", zipname)
files = collections.OrderedDict()
for dir in sys.path:
if os.path.normcase(os.path.realpath(dir)) == os.path.normcase(os.path.realpath(zipname)):
continue
LOGGER.info("Scanning dir %r", dir)
try:
for module_loader, name, ispkg in pkgutil.iter_modules([dir]):
if name in files:
LOGGER.info("Module %r already found as %r", name, files[name])
continue
files[name] = None
if ispkg:
LOGGER.info("Omitting package %r", name)
continue
module_loader = module_loader.find_module(name)
filename = module_loader.get_filename(name)
source = module_loader.get_source(name)
if source is None:
LOGGER.info("Omitting module %r: no source", name)
continue
if "__file__" in source or "__path__" in source:
LOGGER.info("Omitting module %r: __file__ or __path__ in source", name)
continue
LOGGER.debug("Selecting module %r: %r", name, filename)
files[name] = filename
except OSError, e:
LOGGER.warn("Exeception in dir %r: %s", dir, e)
if os.path.exists(zipname):
if not os.path.isfile(zipname) or os.path.islink(zipname):
raise ValueError("Must be a regular file: %r" % (zipname,))
LOGGER.warn("Zipfile already exists, going to remove it: %r", zipname)
os.unlink(zipname)
f = zipfile.PyZipFile(zipname, "w", zipfile.ZIP_DEFLATED, True)
for filename in files.itervalues():
if filename is not None:
try:
f.writepy(filename)
except RuntimeError, e:
LOGGER.debug("Exclude %r, because of RuntimeError: %s", filename, e)
continue
except IOError, e:
LOGGER.debug("Exclude %r, because of IOError: %s", filename, e)
continue
f.close()
LOGGER.info("Created zip archive %r", zipname)
def finderIsNullFinder(finder):
import quickimport as q
return isinstance(finder, (NullFinder, q.NullFinder))
def finderIsQuickimportFinder(finder):
import quickimport as q
return isinstance(finder, (QuickimportFinder, q.QuickimportFinder ))
def isDirRelevant(dir):
"""
Test is a given directory contains any entries that
could be modules or packages.
:param dir: the directory to inspect
:type dir: str or unicode
:returns: `True` if the directory might contain Python modules or packages.
`False` otherwise.
:rtype: bool
"""
finder = sys.path_importer_cache.get(dir)
if finderIsNullFinder(finder) or isinstance(finder, NullImporter):
# We will never import from this directory
return False
if finderIsQuickimportFinder(finder):
return True
if getattr(sys, "quickimport_cache", {}).get(dir):
# It's in the cache. Therefore it is relevant
return True
relevant, files = readAndAnalyseDir(dir, True)
return relevant or files is None
def readAndAnalyseDir(dir, doStat=None):
"""
Read a given directory and check, if the directory
could contain python modules or packages.
Test is a given directory contains any entries that
could be modules or packages.
:param dir: the directory to inspect
:type dir: str or unicode
:param doStat: If ``True``, analyze the directory content more
thoroughly using stat-based calls.
:returns: A tuple, containing a boolean that indicates,
if the directory might contain Python modules or packages, and
an list of the directory content.
:rtype: bool, list
"""
if not os.path.isabs(dir):
# probably not a regular path
return True, None
isdir = os.path.isdir
if not isdir(dir):
# Not a directory at all
return False, None
listdir = os.listdir
try:
files = listdir(dir)
except Exception:
# Dir is unreadable, assume it contains modules
return True, None
normcase = os.path.normcase
# First pass: look for matching module names
for f in files:
nf = normcase(f)
for s in suffixes:
if nf.endswith(s):
return True, files
if not doStat and IDENTIFIER_RE.match(nf):
return True, files
# second pass: look for packages
if doStat:
join = os.path.join
isfile = os.path.isfile
for f in files:
d = join(dir,f)
if not isdir(d):
continue
try:
dfiles = listdir(d)
except Exception:
# Dir is unreadable, assume it contains modules
return True
for ff in dfiles:
if normcase(ff) in initfiles and isfile(ff):
return True, files
# Nothing suitable found
return False, files
def updateCache(cache, dir, files):
"""
Update a dir in the cache
"""
cache[dir] = frozenset(map(os.path.normcase, files))
def prepareCache(path=None, cache=None):
"""
Create or update the directory cache for :class:`QuickimportFinder`.
:param path: a list of path entries to process
:type path: :class:`list`
:param cache: the cache dictionary. If not given, a new dictionary is used
:type cache: dict
:returns: the cache dictionary
:rtype: :class:`dict`
"""
if path is None:
path = sys.path
if cache is None:
cache = {}
for dir in path:
relevant, files = readAndAnalyseDir(dir, False)
if relevant and files:
updateCache(cache, dir, files)
return cache
class NullFinder(object):
"""
A PEP-302 finder class for the ``sys.path_hooks`` hook.
This class never finds anything.
"""
__slots__ = ()
def find_module(self, fullname, path=None):
return None
nullFinder = NullFinder()
# QuickimportFinder should not have to derive from
# pkgutil.ImpImporter. But pkg_resources in setuptools assumes
# (without justification!) that any path-like importer will be
# derived from pkgutil.ImpImporter. If QuickimportFinder derives from
# object, any attempt to use pkg_resources will fail, e.g.,
# python -c "__requires__='setuptools'; import pkg_resources"
class QuickimportFinder(pkgutil.ImpImporter):
"""
A PEP-302 finder class for the ``sys.path_hooks`` hook.
This class uses the directory cache ``sys.quickimport_cache``
to store the content of directories from ``sys.path`` or
from package specific search path lists.
"""
__slots__ = ("dir")
def __init__(self, dir):
pkgutil.ImpImporter.__init__(self, dir)
self.dir = dir
def find_module(self, fullname, path=None):
dbg("find_module (%s): %r" % (self.dir, fullname), end='')
acquire_lock()
try:
dir = self.dir
try:
files = sys.quickimport_cache[dir]
except Exception, e:
raise ImportError("Can't import %r: No quickimport dir cache for dir %r: %s" % (fullname, dir, e) )
basename = fullname.rsplit('.', 1)[-1]
basenameNormcase = os.path.normcase(basename)
if not basenameNormcase in files:
for s in suffixes:
if (basenameNormcase + s) in files:
break
else:
dbg("")
return None
# this path is a candidate
importer = sys.path_importer_cache.get(dir)
assert importer is self
try:
dbg("testing.. ", end='')
loader = ImpLoader(fullname, *find_module(basename, [dir]))
dbg("found")
return loader
except ImportError, e:
dbg(e)
return None
finally:
release_lock()
def newQuickimportFinder(dir):
"""
A PEP-302 finder factory function for the import hook ``sys.path_hooks``.
This function returns a new finder object of class
:class:`QuickimportFinder` or :class:`NullFinder`, if
*dir* denotes a regular directory. Class :class:`NullFinder` is used,
if the directory does not contain any Python module or package.
If *dir* does not denote a regular directory, this function raises
:exc:`ImportError`.
"""
dbg("newQuickimportFinder, dir: %r" % (dir,))
try:
cache = sys.quickimport_cache
except AttributeError:
pass
else:
if dir in cache:
return QuickimportFinder(dir)
isRelevant, files = readAndAnalyseDir(dir, False)
if files is not None:
if not isRelevant:
return nullFinder
if cache.get(AUTOCHACHE_KEY):
updateCache(cache, dir, files)
return QuickimportFinder(dir)
raise ImportError("no cache for %r" % (dir,))
def install(flags=None, dirs=None):
"""
Install the Quickimport importer.
This function optionally
* removes directories without any modules or packages from
``sys.path``.
* appends the PEP-302 importer :class:`QuickimportFinder`
to the end of the ``sys.path_hooks`` list.
:param flags: A string that contains keywords to control
the Quickimport behavior.
:type flags: :class:`str` or a sequence of strings
:param dirs: A list of directories to cache. If this parameter
is not given, ``sys.path`` is used instead.
:type dirs: sequence of strings
Known keywords in `flags` are
are:
``off``
Disable Quickimport entirely. Useful if you encounter import
problems and want to rule out any influence from Quickimport.
``noCache``
Disable the caching of directories and the Quickimport PEP-302
finder.
``noAutocache``
Disable the automatic addition of directories to the
directory cache. Using this flags limits the usage of
Quickimport to the directories given by the *dirs*
argument.
``filterDirs``
Remove non relevant items from *dirs*. An item is
not relevant, if it is a directory, that does not contain
any Python modules or packages.
"""
if flags is None:
flags = ""
if "off" in flags:
return
if "debug" in flags:
global DEBUG
DEBUG = True
acquire_lock()
try:
if "noCache" not in flags:
dbg("quickimport: installing cache")
sys.quickimport_cache = cache = prepareCache(dirs, getattr(sys, "quickimport_cache", None))
cache[AUTOCHACHE_KEY] = "noAutocache" not in flags
try:
sys.path_hooks.remove(newQuickimportFinder)
except ValueError:
pass
sys.path_hooks.append(newQuickimportFinder)
# in case we are running this file as a script
for dir, finder in sys.path_importer_cache.items():
if (finder is None or
finderIsNullFinder(finder) or
finderIsQuickimportFinder(finder)):
del sys.path_importer_cache[dir]
else:
cache.pop(dir, None)
if "filterDirs" in flags:
dbg("quickimport: filtering dirs")
if dirs is None:
dirs = sys.path
dirs[:] = filter(isDirRelevant, dirs)
finally:
release_lock()
def uninstall():
"""
Uninstall Quickimport
"""
try:
sys.path_hooks.remove(newQuickimportFinder)
except ValueError:
pass
else:
sys.path_importer_cache.clear()
try:
del sys.quickimport_cache
except AttributeError:
pass
if __name__ == '__main__':
import logging
logging.basicConfig(level=logging.DEBUG)
buildZip(*sys.argv[1:])