Any template or component can be cached using the cache
argument to the <%page>, <%def> or <%block> directives:
<%page cached="True"/>
template textThe above template, after being executed the first time, will
store its content within a cache that by default is scoped
within memory. Subsequent calls to the template’s render()
method will return content directly from the cache. When the
Template object itself falls out of scope, its corresponding
cache is garbage collected along with the template.
The caching system requires that a cache backend be installed; this includes either the Beaker package or the dogpile.cache, as well as any other third-party caching libraries that feature Mako integration.
By default, caching will attempt to make use of Beaker.
To use dogpile.cache, the
cache_impl argument must be set; see this argument in the
section Cache Arguments.
In addition to being available on the <%page> tag, the caching flag and all
its options can be used with the <%def> tag as well:
<%def name="mycomp" cached="True" cache_timeout="60">
other text
</%def>… and equivalently with the <%block> tag, anonymous or named:
<%block cached="True" cache_timeout="60">
other text
</%block>Mako has two cache arguments available on tags that are available in all cases. The rest of the arguments available are specific to a backend.
The two generic tags arguments are:
cached="True" - enable caching for this <%page>,
<%def>, or <%block>.
cache_key - the “key” used to uniquely identify this content
in the cache. Usually, this key is chosen automatically
based on the name of the rendering callable (i.e. body
when used in <%page>, the name of the def when using <%def>,
the explicit or internally-generated name when using <%block>).
Using the cache_key parameter, the key can be overridden
using a fixed or programmatically generated value.
For example, here’s a page that caches any page which inherits from it, based on the filename of the calling template:
<%page cached="True" cache_key="${self.filename}"/>
${next.body()}
## rest of templateOn a Template or TemplateLookup, the
caching can be configured using these arguments:
cache_enabled - Setting this
to False will disable all caching functionality
when the template renders. Defaults to True.
e.g.:
lookup = TemplateLookup(
directories='/path/to/templates',
cache_enabled = False
)cache_impl - The string name of the cache backend
to use. This defaults to 'beaker', indicating
that the ‘beaker’ backend will be used.
cache_args - A dictionary of cache parameters that
will be consumed by the cache backend. See
Using the Beaker Cache Backend and Using the dogpile.cache Backend for examples.
The <%page>, <%def>, and <%block> tags
accept any named argument that starts with the prefix "cache_".
Those arguments are then packaged up and passed along to the
underlying caching implementation, minus the "cache_" prefix.
The actual arguments understood are determined by the backend.
Using the Beaker Cache Backend - Includes arguments understood by Beaker.
Using the dogpile.cache Backend - Includes arguments understood by dogpile.cache.
When using Beaker, new implementations will want to make usage of cache regions so that cache configurations can be maintained externally to templates. These configurations live under named “regions” that can be referred to within templates themselves.
New in version 0.6.0: Support for Beaker cache regions.
For example, suppose we would like two regions. One is a “short term”
region that will store content in a memory-based dictionary,
expiring after 60 seconds. The other is a Memcached region,
where values should expire in five minutes. To configure
our TemplateLookup, first we get a handle to a
beaker.cache.CacheManager:
from beaker.cache import CacheManager
manager = CacheManager(cache_regions={
'short_term':{
'type': 'memory',
'expire': 60
},
'long_term':{
'type': 'ext:memcached',
'url': '127.0.0.1:11211',
'expire': 300
}
})
lookup = TemplateLookup(
directories=['/path/to/templates'],
module_directory='/path/to/modules',
cache_impl='beaker',
cache_args={
'manager':manager
}
)Our templates can then opt to cache data in one of either region,
using the cache_region argument. Such as using short_term
at the <%page> level:
<%page cached="True" cache_region="short_term">
## ...Or, long_term at the <%block> level:
<%block name="header" cached="True" cache_region="long_term">
other text
</%block>The Beaker backend also works without regions. There are a
variety of arguments that can be passed to the cache_args
dictionary, which are also allowable in templates via the
<%page>, <%block>,
and <%def> tags specific to those sections. The values
given override those specified at the TemplateLookup
or Template level.
With the possible exception
of cache_timeout, these arguments are probably better off
staying at the template configuration level. Each argument
specified as cache_XYZ in a template tag is specified
without the cache_ prefix in the cache_args dictionary:
cache_timeout - number of seconds in which to invalidate the
cached data. After this timeout, the content is re-generated
on the next call. Available as timeout in the cache_args
dictionary.
cache_type - type of caching. 'memory', 'file', 'dbm', or
'ext:memcached' (note that the string memcached is
also accepted by the dogpile.cache Mako plugin, though not by Beaker itself).
Available as type in the cache_args dictionary.
cache_url - (only used for memcached but required) a single
IP address or a semi-colon separated list of IP address of
memcache servers to use. Available as url in the cache_args
dictionary.
cache_dir - in the case of the 'file' and 'dbm' cache types,
this is the filesystem directory with which to store data
files. If this option is not present, the value of
module_directory is used (i.e. the directory where compiled
template modules are stored). If neither option is available
an exception is thrown. Available as dir in the
cache_args dictionary.
dogpile.cache is a new replacement for Beaker. It provides
a modernized, slimmed down interface and is generally easier to use
than Beaker. As of this writing it has not yet been released. dogpile.cache
includes its own Mako cache plugin – see dogpile.cache.plugins.mako_cache in the
dogpile.cache documentation.
The Template, as well as any template-derived Namespace, has
an accessor called cache which returns the Cache object
for that template. This object is a facade on top of the underlying
CacheImpl object, and provides some very rudimental
capabilities, such as the ability to get and put arbitrary
values:
<%
local.cache.set("somekey", type="memory", "somevalue")
%>Above, the cache associated with the local namespace is
accessed and a key is placed within a memory cache.
More commonly, the cache object is used to invalidate cached
sections programmatically:
template = lookup.get_template('/sometemplate.html')
# invalidate the "body" of the template
template.cache.invalidate_body()
# invalidate an individual def
template.cache.invalidate_def('somedef')
# invalidate an arbitrary key
template.cache.invalidate('somekey')You can access any special method or attribute of the CacheImpl
itself using the impl attribute:
template.cache.impl.do_something_special()Note that using implementation-specific methods will mean you can’t
swap in a different kind of CacheImpl implementation at a
later time.
The mechanism used by caching can be plugged in
using a CacheImpl subclass. This class implements
the rudimental methods Mako needs to implement the caching
API. Mako includes the BeakerCacheImpl class to
provide the default implementation. A CacheImpl class
is acquired by Mako using a pkg_resources entrypoint, using
the name given as the cache_impl argument to Template
or TemplateLookup. This entry point can be
installed via the standard setuptools/setup() procedure, underneath
the EntryPoint group named "mako.cache". It can also be
installed at runtime via a convenience installer register_plugin()
which accomplishes essentially the same task.
An example plugin that implements a local dictionary cache:
from mako.cache import Cacheimpl, register_plugin
class SimpleCacheImpl(CacheImpl):
def __init__(self, cache):
super(SimpleCacheImpl, self).__init__(cache)
self._cache = {}
def get_or_create(self, key, creation_function, **kw):
if key in self._cache:
return self._cache[key]
else:
self._cache[key] = value = creation_function()
return value
def set(self, key, value, **kwargs):
self._cache[key] = value
def get(self, key, **kwargs):
return self._cache.get(key)
def invalidate(self, key, **kwargs):
self._cache.pop(key, None)
# optional - register the class locally
register_plugin("simple", __name__, "SimpleCacheImpl")Enabling the above plugin in a template would look like:
t = Template("mytemplate",
file="mytemplate.html",
cache_impl='simple')The CacheImpl is created on a per-Template basis. The
class should ensure that only data for the parent Template is
persisted or returned by the cache methods. The actual Template
is available via the self.cache.template attribute. The self.cache.id
attribute, which is essentially the unique modulename of the template, is
a good value to use in order to represent a unique namespace of keys specific
to the template.
Templates only use the CacheImpl.get_or_create() method
in an implicit fashion. The CacheImpl.set(),
CacheImpl.get(), and CacheImpl.invalidate() methods are
only used in response to direct programmatic access to the corresponding
methods on the Cache object.
CacheImpl will be accessed in a multithreaded fashion if the
Template itself is used multithreaded. Care should be taken
to ensure caching implementations are threadsafe.
A library like Dogpile, which
is a minimal locking system derived from Beaker, can be used to help
implement the CacheImpl.get_or_create() method in a threadsafe
way that can maximize effectiveness across multiple threads as well
as processes. CacheImpl.get_or_create() is the
key method used by templates.
All arguments passed to **kw come directly from the parameters
inside the <%def>, <%block>, or <%page> tags directly,
minus the "cache_" prefix, as strings, with the exception of
the argument cache_timeout, which is passed to the plugin
as the name timeout with the value converted to an integer.
Arguments present in cache_args on Template or
TemplateLookup are passed directly, but are superseded
by those present in the most specific template tag.
The directory where Template places module files can
be acquired using the accessor self.cache.template.module_directory.
This directory can be a good place to throw cache-related work
files, underneath a prefix like _my_cache_work so that name
conflicts with generated modules don’t occur.
mako.cache.Cache(template, *args)¶Bases: object
Represents a data content cache made available to the module
space of a specific Template object.
New in version 0.6: Cache by itself is mostly a
container for a CacheImpl object, which implements
a fixed API to provide caching services; specific subclasses exist to
implement different
caching strategies. Mako includes a backend that works with
the Beaker caching system. Beaker itself then supports
a number of backends (i.e. file, memory, memcached, etc.)
The construction of a Cache is part of the mechanics
of a Template, and programmatic access to this
cache is typically via the Template.cache attribute.
get(key, **kw)¶Retrieve a value from the cache.
get_or_create(key, creation_function, **kw)¶Retrieve a value from the cache, using the given creation function to generate a new value.
id = None¶Return the ‘id’ that identifies this cache.
This is a value that should be globally unique to the
Template associated with this cache, and can
be used by a caching system to name a local container
for data specific to this template.
impl = None¶Provide the CacheImpl in use by this Cache.
This accessor allows a CacheImpl with additional
methods beyond that of Cache to be used programmatically.
invalidate(key, **kw)¶Invalidate a value in the cache.
invalidate_body()¶Invalidate the cached content of the “body” method for this template.
invalidate_closure(name)¶Invalidate a nested <%def> within this template.
Caching of nested defs is a blunt tool as there is no management of scope – nested defs that use cache tags need to have names unique of all other nested defs in the template, else their content will be overwritten by each other.
invalidate_def(name)¶Invalidate the cached content of a particular <%def> within this
template.
put(key, value, **kw)¶A synonym for Cache.set().
This is here for backwards compatibility.
set(key, value, **kw)¶Place a value in the cache.
starttime = None¶Epochal time value for when the owning Template was
first compiled.
A cache implementation may wish to invalidate data earlier than
this timestamp; this has the effect of the cache for a specific
Template starting clean any time the Template
is recompiled, such as when the original template file changed on
the filesystem.
mako.cache.CacheImpl(cache)¶Bases: object
Provide a cache implementation for use by Cache.
get(key, **kw)¶Retrieve a value from the cache.
get_or_create(key, creation_function, **kw)¶Retrieve a value from the cache, using the given creation function to generate a new value.
This function must return a value, either from the cache, or via the given creation function. If the creation function is called, the newly created value should be populated into the cache under the given key before being returned.
invalidate(key, **kw)¶Invalidate a value in the cache.
pass_context = False¶If True, the Context will be passed to
get_or_create as the name 'context'.
mako.cache.register_plugin(name, modulepath, objname)¶mako.ext.beaker_cache.BeakerCacheImpl(cache)¶Bases: mako.cache.CacheImpl
Bases: mako.cache.CacheImpl
A CacheImpl provided for the Beaker caching system.
This plugin is used by default, based on the default
value of 'beaker' for the cache_impl parameter of the
Template or TemplateLookup classes.
get(key, **kw)¶Retrieve a value from the cache.
get_or_create(key, creation_function, **kw)¶Retrieve a value from the cache, using the given creation function to generate a new value.
This function must return a value, either from the cache, or via the given creation function. If the creation function is called, the newly created value should be populated into the cache under the given key before being returned.