Python django.conf.settings.CACHE_MIDDLEWARE_SECONDS Examples

def test_cache(self):
        tmp = settings.CACHE_MIDDLEWARE_SECONDS
        settings.CACHE_MIDDLEWARE_SECONDS = 10

        response = self.client.get(reverse('baseproduct-list'))
        self.assertEqual(response.data['count'], 0)

        args = {"name": "Our Awesome Product", "short": "product", "version": "1", "release_type": "ga"}
        response = self.client.post(reverse('baseproduct-list'), args)
        self.assertEqual(status.HTTP_201_CREATED, response.status_code)

        response = self.client.get(reverse('baseproduct-list'))
        self.assertEqual(response.data['count'], 0)
        self.assertTrue(response.has_header('Cache-Control'))
        self.assertTrue(response.has_header('Last-Modified'))

        time.sleep(11)
        response = self.client.get(reverse('baseproduct-list'))
        self.assertEqual(response.data['count'], 1)

        settings.CACHE_MIDDLEWARE_SECONDS = tmp 

def patch_response_headers(response, cache_timeout=None):
    """
    Adds some useful headers to the given HttpResponse object:
        ETag, Last-Modified, Expires and Cache-Control

    Each header is only added if it isn't already set.

    cache_timeout is in seconds. The CACHE_MIDDLEWARE_SECONDS setting is used
    by default.
    """
    if cache_timeout is None:
        cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
    if cache_timeout < 0:
        cache_timeout = 0  # Can't have max-age negative
    if settings.USE_ETAGS and not response.has_header('ETag'):
        if hasattr(response, 'render') and callable(response.render):
            response.add_post_render_callback(_set_response_etag)
        else:
            response = _set_response_etag(response)
    if not response.has_header('Last-Modified'):
        response['Last-Modified'] = http_date()
    if not response.has_header('Expires'):
        response['Expires'] = http_date(time.time() + cache_timeout)
    patch_cache_control(response, max_age=cache_timeout) 

def patch_response_headers(response, cache_timeout=None):
    """
    Adds some useful headers to the given HttpResponse object:
        ETag, Last-Modified, Expires and Cache-Control

    Each header is only added if it isn't already set.

    cache_timeout is in seconds. The CACHE_MIDDLEWARE_SECONDS setting is used
    by default.
    """
    if cache_timeout is None:
        cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
    if cache_timeout < 0:
        cache_timeout = 0  # Can't have max-age negative
    if settings.USE_ETAGS and not response.has_header('ETag'):
        if hasattr(response, 'render') and callable(response.render):
            response.add_post_render_callback(set_response_etag)
        else:
            response = set_response_etag(response)
    if not response.has_header('Last-Modified'):
        response['Last-Modified'] = http_date()
    if not response.has_header('Expires'):
        response['Expires'] = http_date(time.time() + cache_timeout)
    patch_cache_control(response, max_age=cache_timeout) 

def patch_response_headers(response, cache_timeout=None):
    """
    Add HTTP caching headers to the given HttpResponse: Expires and
    Cache-Control.

    Each header is only added if it isn't already set.

    cache_timeout is in seconds. The CACHE_MIDDLEWARE_SECONDS setting is used
    by default.
    """
    if cache_timeout is None:
        cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
    if cache_timeout < 0:
        cache_timeout = 0  # Can't have max-age negative
    if not response.has_header('Expires'):
        response['Expires'] = http_date(time.time() + cache_timeout)
    patch_cache_control(response, max_age=cache_timeout) 

def patch_response_headers(response, cache_timeout=None):
    """
    Adds some useful headers to the given HttpResponse object:
        ETag, Last-Modified, Expires and Cache-Control

    Each header is only added if it isn't already set.

    cache_timeout is in seconds. The CACHE_MIDDLEWARE_SECONDS setting is used
    by default.
    """
    if cache_timeout is None:
        cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
    if cache_timeout < 0:
        cache_timeout = 0 # Can't have max-age negative
    if settings.USE_ETAGS and not response.has_header('ETag'):
        if hasattr(response, 'render') and callable(response.render):
            response.add_post_render_callback(_set_response_etag)
        else:
            response = _set_response_etag(response)
    if not response.has_header('Last-Modified'):
        response['Last-Modified'] = http_date()
    if not response.has_header('Expires'):
        response['Expires'] = http_date(time.time() + cache_timeout)
    patch_cache_control(response, max_age=cache_timeout) 

def __init__(self, cache_timeout=None, **kwargs):
        # We need to differentiate between "provided, but using default value",
        # and "not provided". If the value is provided using a default, then
        # we fall back to system defaults. If it is not provided at all,
        # we need to use middleware defaults.

        try:
            key_prefix = kwargs['key_prefix']
            if key_prefix is None:
                key_prefix = ''
        except KeyError:
            key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX
        self.key_prefix = key_prefix

        try:
            cache_alias = kwargs['cache_alias']
            if cache_alias is None:
                cache_alias = DEFAULT_CACHE_ALIAS
        except KeyError:
            cache_alias = settings.CACHE_MIDDLEWARE_ALIAS
        self.cache_alias = cache_alias

        if cache_timeout is None:
            cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
        self.cache_timeout = cache_timeout
        self.cache = caches[self.cache_alias] 

def learn_cache_key(request, response, cache_timeout=None, key_prefix=None, cache=None):
    """
    Learns what headers to take into account for some request URL from the
    response object. It stores those headers in a global URL registry so that
    later access to that URL will know what headers to take into account
    without building the response object itself. The headers are named in the
    Vary header of the response, but we want to prevent response generation.

    The list of headers to use for cache key generation is stored in the same
    cache as the pages themselves. If the cache ages some data out of the
    cache, this just means that we have to build the response once to get at
    the Vary header and so at the list of headers to use for the cache key.
    """
    if key_prefix is None:
        key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX
    if cache_timeout is None:
        cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
    cache_key = _generate_cache_header_key(key_prefix, request)
    if cache is None:
        cache = caches[settings.CACHE_MIDDLEWARE_ALIAS]
    if response.has_header('Vary'):
        is_accept_language_redundant = settings.USE_I18N or settings.USE_L10N
        # If i18n or l10n are used, the generated cache key will be suffixed
        # with the current locale. Adding the raw value of Accept-Language is
        # redundant in that case and would result in storing the same content
        # under multiple keys in the cache. See #18191 for details.
        headerlist = []
        for header in cc_delim_re.split(response['Vary']):
            header = header.upper().replace('-', '_')
            if header == 'ACCEPT_LANGUAGE' and is_accept_language_redundant:
                continue
            headerlist.append('HTTP_' + header)
        headerlist.sort()
        cache.set(cache_key, headerlist, cache_timeout)
        return _generate_cache_key(request, request.method, headerlist, key_prefix)
    else:
        # if there is no Vary header, we still need a cache key
        # for the request.build_absolute_uri()
        cache.set(cache_key, [], cache_timeout)
        return _generate_cache_key(request, request.method, [], key_prefix) 

def patch_response_headers(response, cache_timeout=None):
    """
    Add HTTP caching headers to the given HttpResponse: Expires and
    Cache-Control.

    Each header is only added if it isn't already set.

    cache_timeout is in seconds. The CACHE_MIDDLEWARE_SECONDS setting is used
    by default.
    """
    if cache_timeout is None:
        cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
    if cache_timeout < 0:
        cache_timeout = 0  # Can't have max-age negative
    if settings.USE_ETAGS and not response.has_header('ETag'):
        warnings.warn(
            "The USE_ETAGS setting is deprecated in favor of "
            "ConditionalGetMiddleware which sets the ETag regardless of the "
            "setting. patch_response_headers() won't do ETag processing in "
            "Django 2.1.",
            RemovedInDjango21Warning
        )
        if hasattr(response, 'render') and callable(response.render):
            response.add_post_render_callback(set_response_etag)
        else:
            response = set_response_etag(response)
    if not response.has_header('Expires'):
        response['Expires'] = http_date(time.time() + cache_timeout)
    patch_cache_control(response, max_age=cache_timeout) 

def __init__(self, get_response=None, cache_timeout=None, **kwargs):
        self.get_response = get_response
        # We need to differentiate between "provided, but using default value",
        # and "not provided". If the value is provided using a default, then
        # we fall back to system defaults. If it is not provided at all,
        # we need to use middleware defaults.

        try:
            key_prefix = kwargs['key_prefix']
            if key_prefix is None:
                key_prefix = ''
        except KeyError:
            key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX
        self.key_prefix = key_prefix

        try:
            cache_alias = kwargs['cache_alias']
            if cache_alias is None:
                cache_alias = DEFAULT_CACHE_ALIAS
        except KeyError:
            cache_alias = settings.CACHE_MIDDLEWARE_ALIAS
        self.cache_alias = cache_alias

        if cache_timeout is None:
            cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
        self.cache_timeout = cache_timeout
        self.cache = caches[self.cache_alias] 

def __init__(self, get_response=None):
        self.cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
        self.key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX
        self.cache_alias = settings.CACHE_MIDDLEWARE_ALIAS
        self.cache = caches[self.cache_alias]
        self.get_response = get_response 

def learn_cache_key(request, response, cache_timeout=None, key_prefix=None, cache=None):
    """
    Learns what headers to take into account for some request URL from the
    response object. It stores those headers in a global URL registry so that
    later access to that URL will know what headers to take into account
    without building the response object itself. The headers are named in the
    Vary header of the response, but we want to prevent response generation.

    The list of headers to use for cache key generation is stored in the same
    cache as the pages themselves. If the cache ages some data out of the
    cache, this just means that we have to build the response once to get at
    the Vary header and so at the list of headers to use for the cache key.
    """
    if key_prefix is None:
        key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX
    if cache_timeout is None:
        cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
    cache_key = _generate_cache_header_key(key_prefix, request)
    if cache is None:
        cache = caches[settings.CACHE_MIDDLEWARE_ALIAS]
    if response.has_header('Vary'):
        is_accept_language_redundant = settings.USE_I18N or settings.USE_L10N
        # If i18n or l10n are used, the generated cache key will be suffixed
        # with the current locale. Adding the raw value of Accept-Language is
        # redundant in that case and would result in storing the same content
        # under multiple keys in the cache. See #18191 for details.
        headerlist = []
        for header in cc_delim_re.split(response['Vary']):
            header = header.upper().replace('-', '_')
            if header == 'ACCEPT_LANGUAGE' and is_accept_language_redundant:
                continue
            headerlist.append('HTTP_' + header)
        headerlist.sort()
        cache.set(cache_key, headerlist, cache_timeout)
        return _generate_cache_key(request, request.method, headerlist, key_prefix)
    else:
        # if there is no Vary header, we still need a cache key
        # for the request.build_absolute_uri()
        cache.set(cache_key, [], cache_timeout)
        return _generate_cache_key(request, request.method, [], key_prefix) 

def __init__(self, cache_timeout=None, **kwargs):
        # We need to differentiate between "provided, but using default value",
        # and "not provided". If the value is provided using a default, then
        # we fall back to system defaults. If it is not provided at all,
        # we need to use middleware defaults.

        try:
            key_prefix = kwargs['key_prefix']
            if key_prefix is None:
                key_prefix = ''
        except KeyError:
            key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX
        self.key_prefix = key_prefix

        try:
            cache_alias = kwargs['cache_alias']
            if cache_alias is None:
                cache_alias = DEFAULT_CACHE_ALIAS
        except KeyError:
            cache_alias = settings.CACHE_MIDDLEWARE_ALIAS
        self.cache_alias = cache_alias

        if cache_timeout is None:
            cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
        self.cache_timeout = cache_timeout
        self.cache = caches[self.cache_alias] 

def __init__(self):
        self.cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
        self.key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX
        self.cache_alias = settings.CACHE_MIDDLEWARE_ALIAS
        self.cache = caches[self.cache_alias] 

def learn_cache_key(request, response, cache_timeout=None, key_prefix=None, cache=None):
    """
    Learns what headers to take into account for some request path from the
    response object. It stores those headers in a global path registry so that
    later access to that path will know what headers to take into account
    without building the response object itself. The headers are named in the
    Vary header of the response, but we want to prevent response generation.

    The list of headers to use for cache key generation is stored in the same
    cache as the pages themselves. If the cache ages some data out of the
    cache, this just means that we have to build the response once to get at
    the Vary header and so at the list of headers to use for the cache key.
    """
    if key_prefix is None:
        key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX
    if cache_timeout is None:
        cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
    cache_key = _generate_cache_header_key(key_prefix, request)
    if cache is None:
        cache = get_cache(settings.CACHE_MIDDLEWARE_ALIAS)
    if response.has_header('Vary'):
        headerlist = ['HTTP_'+header.upper().replace('-', '_')
                      for header in cc_delim_re.split(response['Vary'])]
        cache.set(cache_key, headerlist, cache_timeout)
        return _generate_cache_key(request, request.method, headerlist, key_prefix)
    else:
        # if there is no Vary header, we still need a cache key
        # for the request.get_full_path()
        cache.set(cache_key, [], cache_timeout)
        return _generate_cache_key(request, request.method, [], key_prefix) 

def __init__(self, cache_timeout=None, cache_anonymous_only=None, **kwargs):
        # We need to differentiate between "provided, but using default value",
        # and "not provided". If the value is provided using a default, then
        # we fall back to system defaults. If it is not provided at all,
        # we need to use middleware defaults.

        cache_kwargs = {}

        try:
            self.key_prefix = kwargs['key_prefix']
            if self.key_prefix is not None:
                cache_kwargs['KEY_PREFIX'] = self.key_prefix
            else:
                self.key_prefix = ''
        except KeyError:
            self.key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX
            cache_kwargs['KEY_PREFIX'] = self.key_prefix

        try:
            self.cache_alias = kwargs['cache_alias']
            if self.cache_alias is None:
                self.cache_alias = DEFAULT_CACHE_ALIAS
            if cache_timeout is not None:
                cache_kwargs['TIMEOUT'] = cache_timeout
        except KeyError:
            self.cache_alias = settings.CACHE_MIDDLEWARE_ALIAS
            if cache_timeout is None:
                cache_kwargs['TIMEOUT'] = settings.CACHE_MIDDLEWARE_SECONDS
            else:
                cache_kwargs['TIMEOUT'] = cache_timeout

        if cache_anonymous_only is None:
            self.cache_anonymous_only = getattr(settings, 'CACHE_MIDDLEWARE_ANONYMOUS_ONLY', False)
        else:
            self.cache_anonymous_only = cache_anonymous_only

        self.cache = get_cache(self.cache_alias, **cache_kwargs)
        self.cache_timeout = self.cache.default_timeout 

def __init__(self):
        self.cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
        self.key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX
        self.cache_anonymous_only = getattr(settings, 'CACHE_MIDDLEWARE_ANONYMOUS_ONLY', False)
        self.cache_alias = settings.CACHE_MIDDLEWARE_ALIAS
        self.cache = get_cache(self.cache_alias) 

def __init__(self):
        self.cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
        self.key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX
        self.cache_anonymous_only = getattr(settings, 'CACHE_MIDDLEWARE_ANONYMOUS_ONLY', False)
        self.cache_alias = settings.CACHE_MIDDLEWARE_ALIAS
        self.cache = get_cache(self.cache_alias) 

def learn_cache_key(request, response, cache_timeout=None, key_prefix=None, cache=None):
    """
    Learns what headers to take into account for some request URL from the
    response object. It stores those headers in a global URL registry so that
    later access to that URL will know what headers to take into account
    without building the response object itself. The headers are named in the
    Vary header of the response, but we want to prevent response generation.

    The list of headers to use for cache key generation is stored in the same
    cache as the pages themselves. If the cache ages some data out of the
    cache, this just means that we have to build the response once to get at
    the Vary header and so at the list of headers to use for the cache key.
    """
    if key_prefix is None:
        key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX
    if cache_timeout is None:
        cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
    cache_key = _generate_cache_header_key(key_prefix, request)
    if cache is None:
        cache = caches[settings.CACHE_MIDDLEWARE_ALIAS]
    if response.has_header('Vary'):
        is_accept_language_redundant = settings.USE_I18N or settings.USE_L10N
        # If i18n or l10n are used, the generated cache key will be suffixed
        # with the current locale. Adding the raw value of Accept-Language is
        # redundant in that case and would result in storing the same content
        # under multiple keys in the cache. See #18191 for details.
        headerlist = []
        for header in cc_delim_re.split(response['Vary']):
            header = header.upper().replace('-', '_')
            if header == 'ACCEPT_LANGUAGE' and is_accept_language_redundant:
                continue
            headerlist.append('HTTP_' + header)
        headerlist.sort()
        cache.set(cache_key, headerlist, cache_timeout)
        return _generate_cache_key(request, request.method, headerlist, key_prefix)
    else:
        # if there is no Vary header, we still need a cache key
        # for the request.build_absolute_uri()
        cache.set(cache_key, [], cache_timeout)
        return _generate_cache_key(request, request.method, [], key_prefix) 

def patch_response_headers(response, cache_timeout=None):
    """
    Add HTTP caching headers to the given HttpResponse: Expires and
    Cache-Control.

    Each header is only added if it isn't already set.

    cache_timeout is in seconds. The CACHE_MIDDLEWARE_SECONDS setting is used
    by default.
    """
    if cache_timeout is None:
        cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
    if cache_timeout < 0:
        cache_timeout = 0  # Can't have max-age negative
    if settings.USE_ETAGS and not response.has_header('ETag'):
        warnings.warn(
            "The USE_ETAGS setting is deprecated in favor of "
            "ConditionalGetMiddleware which sets the ETag regardless of the "
            "setting. patch_response_headers() won't do ETag processing in "
            "Django 2.1.",
            RemovedInDjango21Warning
        )
        if hasattr(response, 'render') and callable(response.render):
            response.add_post_render_callback(set_response_etag)
        else:
            response = set_response_etag(response)
    if not response.has_header('Expires'):
        response['Expires'] = http_date(time.time() + cache_timeout)
    patch_cache_control(response, max_age=cache_timeout) 

def __init__(self, get_response=None, cache_timeout=None, **kwargs):
        self.get_response = get_response
        # We need to differentiate between "provided, but using default value",
        # and "not provided". If the value is provided using a default, then
        # we fall back to system defaults. If it is not provided at all,
        # we need to use middleware defaults.

        try:
            key_prefix = kwargs['key_prefix']
            if key_prefix is None:
                key_prefix = ''
        except KeyError:
            key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX
        self.key_prefix = key_prefix

        try:
            cache_alias = kwargs['cache_alias']
            if cache_alias is None:
                cache_alias = DEFAULT_CACHE_ALIAS
        except KeyError:
            cache_alias = settings.CACHE_MIDDLEWARE_ALIAS
        self.cache_alias = cache_alias

        if cache_timeout is None:
            cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
        self.cache_timeout = cache_timeout
        self.cache = caches[self.cache_alias] 

def __init__(self, get_response=None):
        self.cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
        self.key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX
        self.cache_alias = settings.CACHE_MIDDLEWARE_ALIAS
        self.cache = caches[self.cache_alias]
        self.get_response = get_response 

def learn_cache_key(request, response, cache_timeout=None, key_prefix=None, cache=None):
    """
    Learn what headers to take into account for some request URL from the
    response object. Store those headers in a global URL registry so that
    later access to that URL will know what headers to take into account
    without building the response object itself. The headers are named in the
    Vary header of the response, but we want to prevent response generation.

    The list of headers to use for cache key generation is stored in the same
    cache as the pages themselves. If the cache ages some data out of the
    cache, this just means that we have to build the response once to get at
    the Vary header and so at the list of headers to use for the cache key.
    """
    if key_prefix is None:
        key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX
    if cache_timeout is None:
        cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
    cache_key = _generate_cache_header_key(key_prefix, request)
    if cache is None:
        cache = caches[settings.CACHE_MIDDLEWARE_ALIAS]
    if response.has_header('Vary'):
        is_accept_language_redundant = settings.USE_I18N or settings.USE_L10N
        # If i18n or l10n are used, the generated cache key will be suffixed
        # with the current locale. Adding the raw value of Accept-Language is
        # redundant in that case and would result in storing the same content
        # under multiple keys in the cache. See #18191 for details.
        headerlist = []
        for header in cc_delim_re.split(response['Vary']):
            header = header.upper().replace('-', '_')
            if header != 'ACCEPT_LANGUAGE' or not is_accept_language_redundant:
                headerlist.append('HTTP_' + header)
        headerlist.sort()
        cache.set(cache_key, headerlist, cache_timeout)
        return _generate_cache_key(request, request.method, headerlist, key_prefix)
    else:
        # if there is no Vary header, we still need a cache key
        # for the request.build_absolute_uri()
        cache.set(cache_key, [], cache_timeout)
        return _generate_cache_key(request, request.method, [], key_prefix) 

def __init__(self, get_response=None, cache_timeout=None, **kwargs):
        self.get_response = get_response
        # We need to differentiate between "provided, but using default value",
        # and "not provided". If the value is provided using a default, then
        # we fall back to system defaults. If it is not provided at all,
        # we need to use middleware defaults.

        try:
            key_prefix = kwargs['key_prefix']
            if key_prefix is None:
                key_prefix = ''
        except KeyError:
            key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX
        self.key_prefix = key_prefix

        try:
            cache_alias = kwargs['cache_alias']
            if cache_alias is None:
                cache_alias = DEFAULT_CACHE_ALIAS
        except KeyError:
            cache_alias = settings.CACHE_MIDDLEWARE_ALIAS
        self.cache_alias = cache_alias

        if cache_timeout is None:
            cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
        self.cache_timeout = cache_timeout
        self.cache = caches[self.cache_alias] 

def __init__(self, get_response=None):
        self.cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
        self.key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX
        self.cache_alias = settings.CACHE_MIDDLEWARE_ALIAS
        self.cache = caches[self.cache_alias]
        self.get_response = get_response 

def learn_cache_key(request, response, cache_timeout=None, key_prefix=None, cache=None):
    """
    Learn what headers to take into account for some request URL from the
    response object. Store those headers in a global URL registry so that
    later access to that URL will know what headers to take into account
    without building the response object itself. The headers are named in the
    Vary header of the response, but we want to prevent response generation.

    The list of headers to use for cache key generation is stored in the same
    cache as the pages themselves. If the cache ages some data out of the
    cache, this just means that we have to build the response once to get at
    the Vary header and so at the list of headers to use for the cache key.
    """
    if key_prefix is None:
        key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX
    if cache_timeout is None:
        cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
    cache_key = _generate_cache_header_key(key_prefix, request)
    if cache is None:
        cache = caches[settings.CACHE_MIDDLEWARE_ALIAS]
    if response.has_header('Vary'):
        is_accept_language_redundant = settings.USE_I18N or settings.USE_L10N
        # If i18n or l10n are used, the generated cache key will be suffixed
        # with the current locale. Adding the raw value of Accept-Language is
        # redundant in that case and would result in storing the same content
        # under multiple keys in the cache. See #18191 for details.
        headerlist = []
        for header in cc_delim_re.split(response['Vary']):
            header = header.upper().replace('-', '_')
            if header == 'ACCEPT_LANGUAGE' and is_accept_language_redundant:
                continue
            headerlist.append('HTTP_' + header)
        headerlist.sort()
        cache.set(cache_key, headerlist, cache_timeout)
        return _generate_cache_key(request, request.method, headerlist, key_prefix)
    else:
        # if there is no Vary header, we still need a cache key
        # for the request.build_absolute_uri()
        cache.set(cache_key, [], cache_timeout)
        return _generate_cache_key(request, request.method, [], key_prefix) 

def patch_response_headers(response, cache_timeout=None):
    """
    Add HTTP caching headers to the given HttpResponse: Expires and
    Cache-Control.

    Each header is only added if it isn't already set.

    cache_timeout is in seconds. The CACHE_MIDDLEWARE_SECONDS setting is used
    by default.
    """
    if cache_timeout is None:
        cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
    if cache_timeout < 0:
        cache_timeout = 0  # Can't have max-age negative
    if settings.USE_ETAGS and not response.has_header('ETag'):
        warnings.warn(
            "The USE_ETAGS setting is deprecated in favor of "
            "ConditionalGetMiddleware which sets the ETag regardless of the "
            "setting. patch_response_headers() won't do ETag processing in "
            "Django 2.1.",
            RemovedInDjango21Warning
        )
        if hasattr(response, 'render') and callable(response.render):
            response.add_post_render_callback(set_response_etag)
        else:
            response = set_response_etag(response)
    if not response.has_header('Expires'):
        response['Expires'] = http_date(time.time() + cache_timeout)
    patch_cache_control(response, max_age=cache_timeout) 

def __init__(self, get_response=None, cache_timeout=None, **kwargs):
        self.get_response = get_response
        # We need to differentiate between "provided, but using default value",
        # and "not provided". If the value is provided using a default, then
        # we fall back to system defaults. If it is not provided at all,
        # we need to use middleware defaults.

        try:
            key_prefix = kwargs['key_prefix']
            if key_prefix is None:
                key_prefix = ''
        except KeyError:
            key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX
        self.key_prefix = key_prefix

        try:
            cache_alias = kwargs['cache_alias']
            if cache_alias is None:
                cache_alias = DEFAULT_CACHE_ALIAS
        except KeyError:
            cache_alias = settings.CACHE_MIDDLEWARE_ALIAS
        self.cache_alias = cache_alias

        if cache_timeout is None:
            cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
        self.cache_timeout = cache_timeout
        self.cache = caches[self.cache_alias] 

def __init__(self, get_response=None):
        self.cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
        self.key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX
        self.cache_alias = settings.CACHE_MIDDLEWARE_ALIAS
        self.cache = caches[self.cache_alias]
        self.get_response = get_response 

def learn_cache_key(request, response, cache_timeout=None, key_prefix=None, cache=None):
    """
    Learns what headers to take into account for some request URL from the
    response object. It stores those headers in a global URL registry so that
    later access to that URL will know what headers to take into account
    without building the response object itself. The headers are named in the
    Vary header of the response, but we want to prevent response generation.

    The list of headers to use for cache key generation is stored in the same
    cache as the pages themselves. If the cache ages some data out of the
    cache, this just means that we have to build the response once to get at
    the Vary header and so at the list of headers to use for the cache key.
    """
    if key_prefix is None:
        key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX
    if cache_timeout is None:
        cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
    cache_key = _generate_cache_header_key(key_prefix, request)
    if cache is None:
        cache = caches[settings.CACHE_MIDDLEWARE_ALIAS]
    if response.has_header('Vary'):
        is_accept_language_redundant = settings.USE_I18N or settings.USE_L10N
        # If i18n or l10n are used, the generated cache key will be suffixed
        # with the current locale. Adding the raw value of Accept-Language is
        # redundant in that case and would result in storing the same content
        # under multiple keys in the cache. See #18191 for details.
        headerlist = []
        for header in cc_delim_re.split(response['Vary']):
            header = header.upper().replace('-', '_')
            if header == 'ACCEPT_LANGUAGE' and is_accept_language_redundant:
                continue
            headerlist.append('HTTP_' + header)
        headerlist.sort()
        cache.set(cache_key, headerlist, cache_timeout)
        return _generate_cache_key(request, request.method, headerlist, key_prefix)
    else:
        # if there is no Vary header, we still need a cache key
        # for the request.build_absolute_uri()
        cache.set(cache_key, [], cache_timeout)
        return _generate_cache_key(request, request.method, [], key_prefix) 

def __init__(self):
        self.cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
        self.key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX
        self.cache_alias = settings.CACHE_MIDDLEWARE_ALIAS
        self.cache = caches[self.cache_alias]