EVOLUTION-MANAGER

Edit File: manager.py

#
# manager.py -- Extension management and registration.
#
# Copyright (c) 2010-2013  Beanbag, Inc.
# Copyright (c) 2008-2010  Christian Hammond
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#
# The above copyright notice and this permission notice shall be included
# in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
# IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
# CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
# TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
# SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

from __future__ import unicode_literals

import atexit
import datetime
import errno
import logging
import os
import pkg_resources
import shutil
import sys
import tempfile
import threading
import time
import traceback
import weakref

from django.conf import settings
from django.conf.urls import patterns, include
from django.contrib.admin.sites import AdminSite
from django.core.cache import cache
from django.core.management import call_command
from django.core.management.base import CommandError
from django.core.management.color import no_style
from django.core.urlresolvers import reverse
from django.db import IntegrityError
from django.db.models import loading
from django.utils import six
from django.utils.importlib import import_module
from django.utils.module_loading import module_has_submodule
from django.utils.six.moves import cStringIO as StringIO
from django.utils.translation import ugettext as _
from setuptools.command import easy_install

try:
    from django.template.loader import template_source_loaders
    template_engines = None
except ImportError:
    from django.template import engines as template_engines
    template_source_loaders = None

from djblets.cache.backend import make_cache_key
from djblets.extensions.errors import (EnablingExtensionError,
                                       InstallExtensionError,
                                       InvalidExtensionError)
from djblets.extensions.extension import ExtensionInfo
from djblets.extensions.models import RegisteredExtension
from djblets.extensions.signals import (extension_initialized,
                                        extension_uninitialized)
from djblets.urls.resolvers import DynamicURLResolver
from djblets.util.compat.django.core.files import locks

logger = logging.getLogger(__name__)

class SettingListWrapper(object):
    """Wraps list-based settings to provide management and ref counting.

This can be used instead of direct access to a list in Django
    settings to ensure items are never added more than once, and only
    removed when nothing needs it anymore.

Each item in the list is ref-counted. The initial items from the
    setting are populated and start with a ref count of 1. Adding items
    will increment a ref count for the item, adding it to the list
    if it doesn't already exist. Removing items reduces the ref count,
    removing when it hits 0.
    """
    def __init__(self, setting_name, display_name):
        self.setting_name = setting_name
        self.display_name = display_name
        self.ref_counts = {}

self.setting = getattr(settings, setting_name)

if isinstance(self.setting, tuple):
            self.setting = list(self.setting)
            setattr(settings, setting_name, self.setting)

for item in self.setting:
            self.ref_counts[item] = 1

def add(self, item):
        """Adds an item to the setting.

If the item is already in the list, it won't be added again.
        The ref count will just be incremented.

If it's a new item, it will be added to the list with a ref count
        of 1.
        """
        if item in self.ref_counts:
            self.ref_counts[item] += 1
        else:
            assert item not in self.setting, \
                ("Extension's %s %s is already in settings.%s, with "
                 "ref count of 0."
                 % (self.display_name, item, self.setting_name))

self.ref_counts[item] = 1
            self.setting.append(item)

def add_list(self, items):
        """Adds a list of items to the setting."""
        for item in items:
            self.add(item)

def remove(self, item):
        """Removes an item from the setting.

The item's ref count will be decremented. If it hits 0, it will
        be removed from the list.
        """
        assert item in self.ref_counts, \
            ("Extension's %s %s is missing a ref count."
             % (self.display_name, item))
        assert item in self.setting, \
            ("Extension's %s %s is not in settings.%s"
             % (self.display_name, item, self.setting_name))

if self.ref_counts[item] == 1:
            del self.ref_counts[item]
            self.setting.remove(item)
        else:
            self.ref_counts[item] -= 1

def remove_list(self, items):
        """Removes a list of items from the setting."""
        for item in items:
            try:
                self.remove(item)
            except ValueError:
                # This may have already been removed. Ignore the error.
                pass

class ExtensionManager(object):
    """A manager for all extensions.

ExtensionManager manages the extensions available to a project. It can
    scan for new extensions, enable or disable them, determine dependencies,
    install into the database, and uninstall.

An installed extension is one that has been installed by a Python package
    on the system.

A registered extension is one that has been installed and information then
    placed in the database. This happens automatically after scanning for
    an installed extension. The registration data stores whether or not it's
    enabled, and stores various pieces of information on the extension.

An enabled extension is one that is actively enabled and hooked into the
    project.

Each project should have one ExtensionManager.
    """
    VERSION_SETTINGS_KEY = '_extension_installed_version'

def __init__(self, key):
        self.key = key

self.pkg_resources = None

self._extension_classes = {}
        self._extension_instances = {}
        self._load_errors = {}

# State synchronization
        self._sync_key = make_cache_key('extensionmgr:%s:gen' % key)
        self._last_sync_gen = None
        self._load_lock = threading.Lock()
        self._shutdown_lock = threading.Lock()
        self._block_sync_gen = False

self.dynamic_urls = DynamicURLResolver()

# Extension middleware instances, ordered by dependencies.
        self.middleware = []

# Wrap the INSTALLED_APPS and TEMPLATE_CONTEXT_PROCESSORS settings
        # to allow for ref-counted add/remove operations.
        self._installed_apps_setting = SettingListWrapper(
            'INSTALLED_APPS',
            'installed app')
        self._context_processors_setting = SettingListWrapper(
            'TEMPLATE_CONTEXT_PROCESSORS',
            'context processor')

instance_id = id(self)
        _extension_managers[instance_id] = self

def get_url_patterns(self):
        """Returns the URL patterns for the Extension Manager.

This should be included in the root urlpatterns for the site.
        """
        return patterns('', self.dynamic_urls)

def is_expired(self):
        """Returns whether or not the extension state is possibly expired.

Extension state covers the lists of extensions and each extension's
        configuration. It can expire if the state synchronization value
        falls out of cache or is changed.

Each ExtensionManager has its own state synchronization cache key.
        """
        sync_gen = cache.get(self._sync_key)

return (sync_gen is None or
                (type(sync_gen) is int and sync_gen != self._last_sync_gen))

def clear_sync_cache(self):
        cache.delete(self._sync_key)

def get_absolute_url(self):
        return reverse("djblets.extensions.views.extension_list")

def get_can_disable_extension(self, registered_extension):
        extension_id = registered_extension.class_name

return (registered_extension.extension_class is not None and
                (self.get_enabled_extension(extension_id) is not None or
                 extension_id in self._load_errors))

def get_can_enable_extension(self, registered_extension):
        return (registered_extension.extension_class is not None and
                self.get_enabled_extension(
                    registered_extension.class_name) is None)

def get_enabled_extension(self, extension_id):
        """Returns an enabled extension with the given ID."""
        if extension_id in self._extension_instances:
            return self._extension_instances[extension_id]

return None

def get_enabled_extensions(self):
        """Returns the list of all enabled extensions."""
        return list(self._extension_instances.values())

def get_installed_extensions(self):
        """Returns the list of all installed extensions."""
        return list(self._extension_classes.values())

def get_installed_extension(self, extension_id):
        """Returns the installed extension with the given ID."""
        if extension_id not in self._extension_classes:
            raise InvalidExtensionError(extension_id)

return self._extension_classes[extension_id]

def get_dependent_extensions(self, dependency_extension_id):
        """Returns a list of all extensions required by an extension."""
        if dependency_extension_id not in self._extension_instances:
            raise InvalidExtensionError(dependency_extension_id)

dependency = self.get_installed_extension(dependency_extension_id)
        result = []

for extension_id, extension in six.iteritems(self._extension_classes):
            if extension_id == dependency_extension_id:
                continue

for ext_requirement in extension.info.requirements:
                if ext_requirement == dependency:
                    result.append(extension_id)

return result

def enable_extension(self, extension_id):
        """Enables an extension.

Enabling an extension will install any data files the extension
        may need, any tables in the database, perform any necessary
        database migrations, and then will start up the extension.
        """
        if extension_id in self._extension_instances:
            # It's already enabled.
            return

if extension_id not in self._extension_classes:
            if extension_id in self._load_errors:
                raise EnablingExtensionError(
                    _('There was an error loading this extension'),
                    self._load_errors[extension_id],
                    needs_reload=True)

raise InvalidExtensionError(extension_id)

ext_class = self._extension_classes[extension_id]

# Enable extension dependencies
        for requirement_id in ext_class.requirements:
            self.enable_extension(requirement_id)

extension = self._init_extension(ext_class)

ext_class.registration.enabled = True
        ext_class.registration.save()

self._clear_template_cache()
        self._bump_sync_gen()
        self._recalculate_middleware()

return extension

def disable_extension(self, extension_id):
        """Disables an extension.

Disabling an extension will remove any data files the extension
        installed and then shut down the extension and all of its hooks.

It will not delete any data from the database.
        """
        has_load_error = extension_id in self._load_errors

if not has_load_error:
            if extension_id not in self._extension_instances:
                # It's not enabled.
                return

if extension_id not in self._extension_classes:
                raise InvalidExtensionError(extension_id)

extension = self._extension_instances[extension_id]

for dependent_id in self.get_dependent_extensions(extension_id):
                self.disable_extension(dependent_id)

self._uninstall_extension(extension)
            self._uninit_extension(extension)
            self._unregister_static_bundles(extension)

registration = extension.registration
        else:
            del self._load_errors[extension_id]

if extension_id in self._extension_classes:
                # The class was loadable, so it just couldn't be instantiated.
                # Update the registration on the class.
                ext_class = self._extension_classes[extension_id]
                registration = ext_class.registration
            else:
                registration = RegisteredExtension.objects.get(
                    class_name=extension_id)

registration.enabled = False
        registration.save(update_fields=['enabled'])

self._clear_template_cache()
        self._bump_sync_gen()
        self._recalculate_middleware()

def install_extension(self, install_url, package_name):
        """Install an extension from a remote source.

Installs an extension from a remote URL containing the
        extension egg. Installation may fail if a malformed install_url
        or package_name is passed, which will cause an InstallExtensionError
        exception to be raised. It is also assumed that the extension is not
        already installed.
        """

try:
            easy_install.main(["-U", install_url])

# Update the entry points.
            dist = pkg_resources.get_distribution(package_name)
            dist.activate()
            pkg_resources.working_set.add(dist)
        except pkg_resources.DistributionNotFound:
            raise InstallExtensionError(_("Invalid package name."))
        except SystemError:
            raise InstallExtensionError(
                _('Installation failed (probably malformed URL).'))

# Refresh the extension manager.
        self.load(True)

def load(self, full_reload=False):
        """
        Loads all known extensions, initializing any that are recorded as
        being enabled.

If this is called a second time, it will refresh the list of
        extensions, adding new ones and removing deleted ones.

If full_reload is passed, all state is cleared and we reload all
        extensions and state from scratch.
        """
        with self._load_lock:
            self._block_sync_gen = True
            self._load_extensions(full_reload)
            self._block_sync_gen = False

def shutdown(self):
        """Shut down the extension manager and all of its extensions."""
        with self._shutdown_lock:
            self._clear_extensions()

def _load_extensions(self, full_reload=False):
        if full_reload:
            # We're reloading everything, so nuke all the cached copies.
            self._clear_extensions()
            self._clear_template_cache()
            self._load_errors = {}

# Preload all the RegisteredExtension objects
        registered_extensions = {}
        for registered_ext in RegisteredExtension.objects.all():
            registered_extensions[registered_ext.class_name] = registered_ext

found_extensions = {}
        found_registrations = {}
        registrations_to_fetch = []
        find_registrations = False
        extensions_changed = False

for entrypoint in self._entrypoint_iterator():
            registered_ext = None

try:
                ext_class = entrypoint.load()
            except Exception as e:
                logger.exception('Error loading extension %s: %s',
                                 entrypoint.name, e)
                extension_id = '%s.%s' % (entrypoint.module_name,
                                          '.'.join(entrypoint.attrs))
                self._store_load_error(extension_id, e)
                continue

# A class's extension ID is its class name. We want to
            # make this easier for users to access by giving it an 'id'
            # variable, which will be accessible both on the class and on
            # instances.
            class_name = ext_class.id = "%s.%s" % (ext_class.__module__,
                                                   ext_class.__name__)
            self._extension_classes[class_name] = ext_class
            found_extensions[class_name] = ext_class

# Don't override the info if we've previously loaded this
            # class.
            if not getattr(ext_class, 'info', None):
                ext_class.info = ExtensionInfo.create_from_entrypoint(
                    entrypoint, ext_class)

registered_ext = registered_extensions.get(class_name)

if registered_ext:
                found_registrations[class_name] = registered_ext

if not hasattr(ext_class, 'registration'):
                    find_registrations = True
            else:
                registrations_to_fetch.append(
                    (class_name, entrypoint.dist.project_name))
                find_registrations = True

if find_registrations:
            if registrations_to_fetch:
                stored_registrations = list(
                    RegisteredExtension.objects.filter(
                        class_name__in=registrations_to_fetch))

# Go through the list of registrations found in the database
                # and mark them as found for later processing.
                for registered_ext in stored_registrations:
                    class_name = registered_ext.class_name
                    found_registrations[class_name] = registered_ext

# Go through each registration we still need and couldn't find,
            # and create an entry in the database. These are going to be
            # newly discovered extensions.
            for class_name, ext_name in registrations_to_fetch:
                if class_name not in found_registrations:
                    try:
                        registered_ext = RegisteredExtension.objects.create(
                            class_name=class_name,
                            name=ext_name)
                    except IntegrityError:
                        # An entry was created since we last looked up
                        # anything. Fetch it from the database.
                        registered_ext = RegisteredExtension.objects.get(
                            class_name=class_name)

found_registrations[class_name] = registered_ext

# Now we have all the RegisteredExtension instances. Go through
        # and initialize each of them.
        for class_name, registered_ext in six.iteritems(found_registrations):
            ext_class = found_extensions[class_name]
            ext_class.registration = registered_ext

if (ext_class.registration.enabled and
                ext_class.id not in self._extension_instances):

try:
                    self._init_extension(ext_class)
                except EnablingExtensionError:
                    # When in debug mode, we want this error to be noticed.
                    # However, in production, it shouldn't break the whole
                    # server, so continue on.
                    if not settings.DEBUG:
                        continue

extensions_changed = True

# At this point, if we're reloading, it's possible that the user
        # has removed some extensions. Go through and remove any that we
        # can no longer find.
        #
        # While we're at it, since we're at a point where we've seen all
        # extensions, we can set the ExtensionInfo.requirements for
        # each extension
        for class_name, ext_class in six.iteritems(self._extension_classes):
            if class_name not in found_extensions:
                if class_name in self._extension_instances:
                    self.disable_extension(class_name)

del self._extension_classes[class_name]
                extensions_changed = True
            else:
                ext_class.info.requirements = \
                    [self.get_installed_extension(requirement_id)
                     for requirement_id in ext_class.requirements]

# Add the sync generation if it doesn't already exist.
        self._add_new_sync_gen()
        self._last_sync_gen = cache.get(self._sync_key)
        settings.AJAX_SERIAL = self._last_sync_gen

if extensions_changed:
            self._recalculate_middleware()

def _clear_extensions(self):
        """Clear the entire list of known extensions.

This will bring the ExtensionManager back to the state where
        it doesn't yet know about any extensions, requiring a re-load.
        """
        for extension in self.get_enabled_extensions():
            # Make sure this is actually an enabled extension, and not one
            # that's already been shut down by another instance of this
            # ExtensionManager (which should only happen in tests):
            if hasattr(extension.__class__, 'info'):
                self._uninit_extension(extension)

for extension_class in self.get_installed_extensions():
            if hasattr(extension_class, 'info'):
                delattr(extension_class, 'info')

if hasattr(extension_class, 'registration'):
                delattr(extension_class, 'registration')

self._extension_classes = {}
        self._extension_instances = {}

def _clear_template_cache(self):
        """Clears the Django template caches."""
        if template_source_loaders:
            # We're running in Django <=1.7.
            template_loaders = template_source_loaders
        elif template_engines:
            template_loaders = []

for engine in template_engines.all():
                template_loaders += engine.engine.template_loaders
        else:
            # It's valid for there to not be any loaders.
            template_loaders = []

for template_loader in template_loaders:
            if hasattr(template_loader, 'reset'):
                template_loader.reset()

def _init_extension(self, ext_class):
        """Initializes an extension.

This will register the extension, install any URLs that it may need,
        and make it available in Django's list of apps. It will then notify
        that the extension has been initialized.
        """
        extension_id = ext_class.id

assert extension_id not in self._extension_instances

try:
            extension = ext_class(extension_manager=self)
        except Exception as e:
            logger.exception('Unable to initialize extension %s: %s',
                             ext_class, e)
            error_details = self._store_load_error(extension_id, e)
            raise EnablingExtensionError(
                _('Error initializing extension: %s') % e,
                error_details)

if extension_id in self._load_errors:
            del self._load_errors[extension_id]

self._extension_instances[extension_id] = extension

if extension.has_admin_site:
            self._init_admin_site(extension)

# Installing the urls must occur after _init_admin_site(). The urls
        # for the admin site will not be generated until it is called.
        self._install_admin_urls(extension)

self._register_static_bundles(extension)

extension.info.installed = extension.registration.installed
        extension.info.enabled = True
        self._add_to_installed_apps(extension)
        self._context_processors_setting.add_list(extension.context_processors)
        self._reset_templatetags_cache()
        ext_class.instance = extension

try:
            self.install_extension_media(ext_class)
        except InstallExtensionError as e:
            raise EnablingExtensionError(e.message, e.load_error)

extension_initialized.send(self, ext_class=extension)

return extension

def _uninit_extension(self, extension):
        """Uninitializes the extension.

This will shut down the extension, remove any URLs, remove it from
        Django's list of apps, and send a signal saying the extension was
        shut down.
        """
        extension.shutdown()

if hasattr(extension, "admin_urlpatterns"):
            self.dynamic_urls.remove_patterns(
                extension.admin_urlpatterns)

if hasattr(extension, "admin_site_urlpatterns"):
            self.dynamic_urls.remove_patterns(
                extension.admin_site_urlpatterns)

if hasattr(extension, 'admin_site'):
            del extension.admin_site

self._context_processors_setting.remove_list(
            extension.context_processors)
        self._remove_from_installed_apps(extension)
        self._reset_templatetags_cache()
        extension.info.enabled = False
        extension_uninitialized.send(self, ext_class=extension)

del self._extension_instances[extension.id]
        extension.__class__.instance = None

def _store_load_error(self, extension_id, err):
        """Stores and returns a load error for the extension ID."""
        error_details = '%s\n\n%s' % (err, traceback.format_exc())
        self._load_errors[extension_id] = error_details

return error_details

def _reset_templatetags_cache(self):
        """Clears the Django templatetags_modules cache."""
        # We'll import templatetags_modules here because
        # we want the most recent copy of templatetags_modules
        from django.template.base import get_templatetags_modules

# Wipe out the contents.
        if hasattr(get_templatetags_modules, 'cache_clear'):
            # Django >= 1.7
            get_templatetags_modules.cache_clear()
        else:
            # Django < 1.7
            from django.template.base import templatetags_modules
            del(templatetags_modules[:])

# And reload the cache
        get_templatetags_modules()

def install_extension_media(self, ext_class, force=False):
        """Installs extension static media.

This method is a wrapper around _install_extension_media_internal to
        check whether we actually need to install extension media, and avoid
        contention among multiple threads/processes when doing so.

We need to install extension media if it hasn't been installed yet,
        or if the version of the extension media that we installed is different
        from the current version of the extension.
        """
        lockfile = os.path.join(tempfile.gettempdir(), ext_class.id + '.lock')
        extension = ext_class.instance

cur_version = ext_class.info.version

# We only want to fetch the existing version information if the
        # extension is already installed. We remove this key when
        # disabling an extension, so if it were there, it was either
        # copy/pasted, or something went wrong. Either way, we wouldn't
        # be able to trust it.
        if force:
            logger.debug('Forcing installation fo extension media for %s',
                         ext_class.info)
            old_version = None
        else:
            if ext_class.registration.installed:
                old_version = extension.settings.get(self.VERSION_SETTINGS_KEY)
            else:
                old_version = None

if old_version == cur_version:
                # Nothing to do
                return

if not old_version:
                logger.debug('Installing extension media for %s',
                             ext_class.info)
            else:
                logger.debug('Reinstalling extension media for %s because '
                             'version changed from %s',
                             ext_class.info, old_version)

while old_version != cur_version:
            with open(lockfile, 'w') as f:
                try:
                    locks.lock(f, locks.LOCK_EX | locks.LOCK_NB)
                except IOError as e:
                    if e.errno in (errno.EAGAIN, errno.EACCES, errno.EINTR):
                        # Sleep for one second, then try again
                        time.sleep(1)
                        extension.settings.load()
                        old_version = extension.settings.get(
                            self.VERSION_SETTINGS_KEY)
                        continue
                    else:
                        raise e

self._install_extension_media_internal(ext_class)
                extension.settings.set(self.VERSION_SETTINGS_KEY, cur_version)
                extension.settings.save()
                old_version = cur_version

locks.unlock(f)

try:
            os.unlink(lockfile)
        except OSError as e:
            # A "No such file or directory" (ENOENT) is most likely due to
            # another thread removing the lock file before this thread could.
            # It's safe to ignore. We want to handle all others, though.
            if e.errno != errno.ENOENT:
                logger.exception("Failed to unlock media lock file '%s' for "
                                 "extension '%s': %s",
                                 lockfile, ext_class.info, e)

def _install_extension_media_internal(self, ext_class):
        """Installs extension data.

Performs any installation necessary for an extension.

If the extension has a legacy htdocs/ directory for static media
        files, they will be installed into MEDIA_ROOT/ext/, and a warning
        will be logged.

If the extension has a modern static/ directory, they will be
        installed into STATIC_ROOT/ext/.
        """
        ext_htdocs_path = ext_class.info.installed_htdocs_path
        ext_htdocs_path_exists = os.path.exists(ext_htdocs_path)

if ext_htdocs_path_exists:
            # First, get rid of the old htdocs contents, so we can start
            # fresh.
            shutil.rmtree(ext_htdocs_path, ignore_errors=True)

if pkg_resources.resource_exists(ext_class.__module__, 'htdocs'):
            # This is an older extension that doesn't use the static file
            # support. Log a deprecation notice and then install the files.
            logger.warning('The %s extension uses the deprecated "htdocs" '
                           'directory for static files. It should be updated '
                           'to use a "static" directory instead.',
                           ext_class.info.name)

extracted_path = \
                pkg_resources.resource_filename(ext_class.__module__, 'htdocs')

shutil.copytree(extracted_path, ext_htdocs_path, symlinks=True)

# We only want to install static media on a non-DEBUG install.
        # Otherwise, we run the risk of creating a new 'static' directory and
        # causing Django to look up all static files (not just from
        # extensions) from there instead of from their source locations.
        if not settings.DEBUG:
            ext_static_path = ext_class.info.installed_static_path
            ext_static_path_exists = os.path.exists(ext_static_path)

if ext_static_path_exists:
                # Also get rid of the old static contents.
                shutil.rmtree(ext_static_path, ignore_errors=True)

if os.path.exists(ext_static_path):
                    logging.critical('Unable to remove old extension media for '
                                     '%s at %s. Make sure this path, its '
                                     'parent, and everything under it is '
                                     'writable by your web server.',
                                     ext_class.info.name, ext_static_path)

if pkg_resources.resource_exists(ext_class.__module__, 'static'):
                extracted_path = \
                    pkg_resources.resource_filename(ext_class.__module__,
                                                    'static')

try:
                    shutil.copytree(extracted_path, ext_static_path,
                                    symlinks=True)
                except Exception as e:
                    logging.critical('Unable to install extension media for %s '
                                     'to %s: %s. The extension may not work, '
                                     'and pages may crash.',
                                     ext_class.info.name, ext_static_path,
                                     exc_info=True)

# Mark the extension as installed
        ext_class.registration.installed = True
        ext_class.registration.save()

# Now let's build any tables that this extension might need
        self._add_to_installed_apps(ext_class)

# Call syncdb to create the new tables
        loading.cache.loaded = False
        call_command('syncdb', verbosity=0, interactive=False)

# Run evolve to do any table modification.
        self._migrate_extension_models(ext_class)

# Remove this again, since we only needed it for syncdb and
        # evolve.  _init_extension will add it again later in
        # the install.
        self._remove_from_installed_apps(ext_class)

# Mark the extension as installed
        ext_class.registration.installed = True
        ext_class.registration.save()

def _uninstall_extension(self, extension):
        """Uninstalls extension data.

Performs any uninstallation necessary for an extension.

This will uninstall the contents of MEDIA_ROOT/ext/ and
        STATIC_ROOT/ext/.
        """
        extension.settings.set(self.VERSION_SETTINGS_KEY, None)
        extension.settings.save()

extension.registration.installed = False
        extension.registration.save()

for path in (extension.info.installed_htdocs_path,
                     extension.info.installed_static_path):
            if os.path.exists(path):
                shutil.rmtree(path, ignore_errors=True)

def _install_admin_urls(self, extension):
        """Installs administration URLs.

This provides URLs for configuring an extension, plus any additional
        admin urlpatterns that the extension provides.
        """
        prefix = self.get_absolute_url()

if hasattr(settings, 'SITE_ROOT'):
            prefix = prefix[len(settings.SITE_ROOT):]

# Note that we're adding to the resolve list on the root of the
        # install, and prefixing it with the admin extensions path.
        # The reason we're not just making this a child of our extensions
        # urlconf is that everything in there gets passed an
        # extension_manager variable, and we don't want to force extensions
        # to handle this.

if extension.is_configurable:
            urlconf = extension.admin_urlconf
            if hasattr(urlconf, "urlpatterns"):
                extension.admin_urlpatterns = patterns(
                    '',
                    (r'^%s%s/config/' % (prefix, extension.id),
                     include(urlconf.__name__)))

self.dynamic_urls.add_patterns(
                    extension.admin_urlpatterns)

if getattr(extension, 'admin_site', None):
            extension.admin_site_urlpatterns = patterns(
                '',
                (r'^%s%s/db/' % (prefix, extension.id),
                 include(extension.admin_site.urls)))

self.dynamic_urls.add_patterns(
                extension.admin_site_urlpatterns)

def _register_static_bundles(self, extension):
        """Registers the extension's static bundles with Pipeline.

Each static bundle will appear as an entry in Pipeline. The
        bundle name and filenames will be changed to include the extension
        ID for the static file lookups.
        """
        def _add_prefix(filename):
            return 'ext/%s/%s' % (extension.id, filename)

def _add_bundles(pipeline_bundles, extension_bundles, default_dir,
                         ext):
            for name, bundle in six.iteritems(extension_bundles):
                new_bundle = bundle.copy()

new_bundle['source_filenames'] = [
                    _add_prefix(filename)
                    for filename in bundle.get('source_filenames', [])
                ]

new_bundle['output_filename'] = _add_prefix(bundle.get(
                    'output_filename',
                    '%s/%s.min%s' % (default_dir, name, ext)))

pipeline_bundles[extension.get_bundle_id(name)] = new_bundle

if not hasattr(settings, 'PIPELINE_CSS'):
            settings.PIPELINE_CSS = {}

if not hasattr(settings, 'PIPELINE_JS'):
            settings.PIPELINE_JS = {}

_add_bundles(settings.PIPELINE_CSS, extension.css_bundles,
                     'css', '.css')
        _add_bundles(settings.PIPELINE_JS, extension.js_bundles,
                     'js', '.js')

def _unregister_static_bundles(self, extension):
        """Unregisters the extension's static bundles from Pipeline.

Every static bundle previously registered will be removed.
        """
        def _remove_bundles(pipeline_bundles, extension_bundles):
            for name, bundle in six.iteritems(extension_bundles):
                try:
                    del pipeline_bundles[extension.get_bundle_id(name)]
                except KeyError:
                    pass

if hasattr(settings, 'PIPELINE_CSS'):
            _remove_bundles(settings.PIPELINE_CSS, extension.css_bundles)

if hasattr(settings, 'PIPELINE_JS'):
            _remove_bundles(settings.PIPELINE_JS, extension.js_bundles)

def _init_admin_site(self, extension):
        """Creates and initializes an admin site for an extension.

This creates the admin site and imports the extensions admin
        module to register the models.

The url patterns for the admin site are generated in
        _install_admin_urls().
        """
        extension.admin_site = AdminSite(extension.info.app_name)

# Import the extension's admin module.
        try:
            admin_module_name = '%s.admin' % extension.info.app_name
            if admin_module_name in sys.modules:
                # If the extension has been loaded previously and
                # we are re-enabling it, we must reload the module.
                # Just importing again will not cause the ModelAdmins
                # to be registered.
                reload(sys.modules[admin_module_name])
            else:
                import_module(admin_module_name)
        except ImportError:
            mod = import_module(extension.info.app_name)

# Decide whether to bubble up this error. If the app just
            # doesn't have an admin module, we can ignore the error
            # attempting to import it, otherwise we want it to bubble up.
            if module_has_submodule(mod, 'admin'):
                raise ImportError(
                    "Importing admin module for extension %s failed"
                    % extension.info.app_name)

def _add_to_installed_apps(self, extension):
        self._installed_apps_setting.add_list(
            extension.apps or [extension.info.app_name])

def _remove_from_installed_apps(self, extension):
        self._installed_apps_setting.remove_list(
            extension.apps or [extension.info.app_name])

def _entrypoint_iterator(self):
        return pkg_resources.iter_entry_points(self.key)

def _bump_sync_gen(self):
        """Bumps the synchronization generation value.

If there's an existing synchronization generation in cache,
        increment it. Otherwise, start fresh with a new one.

This will also set ``settings.AJAX_SERIAL``, which will guarantee any
        cached objects that depends on templates and use this serial number
        will be invalidated, allowing TemplateHooks and other hooks
        to be re-run.
        """
        # If we're in the middle of loading extension state, perhaps due to
        # the sync number being bumped by another process, this flag will be
        # sent in order to block any further attempts at bumping the number.
        # Failure to do this can result in a loop where the number gets
        # bumped by every process/thread reacting to another process/thread
        # bumping the number, resulting in massive slowdown and errors.
        if self._block_sync_gen:
            return

try:
            self._last_sync_gen = cache.incr(self._sync_key)
        except ValueError:
            self._last_sync_gen = self._add_new_sync_gen()

settings.AJAX_SERIAL = self._last_sync_gen

def _add_new_sync_gen(self):
        val = time.mktime(datetime.datetime.now().timetuple())
        return cache.add(self._sync_key, int(val))

def _migrate_extension_models(self, ext_class):
        """Perform database migrations for an extension's models.

This will call out to Django Evolution to handle the migrations.

Args:
            ext_class (djblets.extensions.extension.Extension):
                The class for the extension to migrate.
        """
        try:
            from django_evolution.management.commands.evolve import \
                Command as Evolution
        except ImportError:
            raise InstallExtensionError(
                "Unable to migrate the extension's database tables. Django "
                "Evolution is not installed.")

try:
            stream = StringIO()
            evolution = Evolution()
            evolution.style = no_style()
            evolution.execute(verbosity=0, interactive=False,
                              execute=True, hint=False,
                              compile_sql=False, purge=False,
                              database=False,
                              stdout=stream, stderr=stream)

output = stream.getvalue()

if output:
                logger.info('Evolved extension models for %s: %s',
                            ext_class.id, stream.read())

stream.close()
        except CommandError as e:
            # Something went wrong while running django-evolution, so
            # grab the output.  We can't raise right away because we
            # still need to put stdout back the way it was
            output = stream.getvalue()
            stream.close()

logger.exception('Error evolving extension models: %s: %s',
                             e, output)

load_error = self._store_load_error(ext_class.id, output)
            raise InstallExtensionError(six.text_type(e), load_error)

def _recalculate_middleware(self):
        """Recalculates the list of middleware."""
        self.middleware = []
        done = set()

for e in self.get_enabled_extensions():
            self.middleware.extend(self._get_extension_middleware(e, done))

def _get_extension_middleware(self, extension, done):
        """Returns a list of middleware for 'extension' and its dependencies.

This is a recursive utility function initially called by
        _recalculate_middleware() that ensures that middleware for all
        dependencies are inserted before that of the given extension.  It
        also ensures that each extension's middleware is inserted only once.
        """
        middleware = []

if extension in done:
            return middleware

done.add(extension)

for req in extension.requirements:
            e = self.get_enabled_extension(req)

if e:
                middleware.extend(self._get_extension_middleware(e, done))

middleware.extend(extension.middleware_instances)
        return middleware

_extension_managers = weakref.WeakValueDictionary()

def get_extension_managers():
    """Return all extension manager instances.

This will return all the extension managers that have been constructed.
    The order is not guaranteed.

Returns:
        list: The list of ExtensionManager instances.
    """
    return _extension_managers.values()

def shutdown_extension_managers():
    """Shut down all extension managers.

This is called automatically when the process exits, but can be run
    manually.
    """
    for extension_manager in get_extension_managers():
        extension_manager.shutdown()

# When the process ends, shut down the extensions on this manager.
# That will help work around bugs in Django where it attempts to
# work with garbage state being held onto by extensions.
atexit.register(shutdown_extension_managers)