[Django] #35524: Add possibility to renew {% cache %} templatetag

[Django]

#35524: Add possibility to renew {% cache %} templatetag
-------------------------------------+-------------------------------------
Reporter: Petr | Owner: nobody
Dlouhý |
Type: New | Status: new
feature |
Component: Template | Version: 5.0
system |
Severity: Normal | Keywords: cache templatetag
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
-------------------------------------+-------------------------------------
The wider context of my use-case is described at:
https://code.djangoproject.com/ticket/5815#comment:17

I have a view which uses templates with `{% cache %}` templatetag.
When the cache timeouts it results results into database hammering -
multiple requests lacking the cache are hitting DB at the same time.
Erasing the cache with `make_template_fragment_key` is not an option
either, it results in the same situation.
I would like to be able to renew the state of cached parts of my template
without erasing the cache key, but rather just setting the new values.

There are two scenarios in which I could use this functionality to solve
my problem:
1) I would create a task/job that will periodically renew the cache on
that page.
2) The cache would use staggering - I randomize the cache timeout to
reduce number of requests without cache. This unfortunately doesn't work,
because the cache key will expire at one time.

I am trying to use the 1) solution - the very easy solution is to modify
the cache templatetag code with something like:

{{{
class CacheNode(Node):
def __init__(self, nodelist, expire_time_var, fragment_name, vary_on,
cache_name, renew_cache=False):
self.renew_cache = renew_cache
...

def render(self, context):
...
value = fragment_cache.get(cache_key)
if value is None or self.renew_cache
value = self.nodelist.render(context)
fragment_cache.set(cache_key, value, expire_time)
return value

...
}}}

Right now I have this custom templatetag, but I am not very happy that I
have to copy and maintain a big portion of code from Django.


I think Django should provide some mechanisms to deal with situations like
this (and ticket #5815 is supporting this claim).
--
Ticket URL: <https://code.djangoproject.com/ticket/35524>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.

[Django]

#35524: Add possibility to renew {% cache %} templatetag

-----------------------------------+--------------------------------------
Reporter: Petr Dlouhý | Owner: nobody
Type: New feature | Status: closed
Component: Template system | Version: 5.0
Severity: Normal | Resolution: wontfix
Keywords: cache templatetag | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0

Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0

-----------------------------------+--------------------------------------
Changes (by Sarah Boyce):

* resolution: => wontfix
* status: new => closed

Comment:

Hi Petr, I can see why you would want a new feature here.

For cases like this, the recommended path forward is to first propose and
discuss the idea with the community and gain consensus on how to push this
forward (this might be complex so a third party package may even be a good
idea here). To do that, please consider starting a new conversation on the
[https://forum.djangoproject.com/c/internals/5 Django Forum], where you'll
reach a wider audience and likely get extra feedback.

I'll close the ticket for now, but if there is a community agreement for
the feature request, you are welcome to come back to the ticket and point
to the forum topic, so we can then re-open it. For more details, please
see [https://docs.djangoproject.com/en/stable/internals/contributing/bugs-
and-features/#requesting-features the documented guidelines for requesting
features].

Thanks!
--
Ticket URL: <https://code.djangoproject.com/ticket/35524#comment:1>