django-上下文处理器变量未更新

Question

I have several variables within a navbar that are to be displayed on every single template, so I've made a custom context processor to handle the fetching of those variables. Everything is working, except that when the data is changed in the database, the values of the context variables are not refreshed(for example it'll only get updated once I quit runserver and rerun).

Here's my basic pseudo code:

context_processor.py:

foo = db.get('foo')
bar = db.get('bar')

def default(request):
    return {'foo': foo, 'bar': bar}

base.html:

{% block header %}
foo value is: {{ foo }}, bar value is {{ bar}}
{% endblock %}

{% block content %}
{% endblock %}

some_other_template.html:

{% extends "base.html" %}

{% block content %}
    ...blabla
{% endblock %}

Is there something I am missing or is this normal behavior? Have I used the wrong approach of using a context processor here?

Answer 1

When Django processes a template, it treats the html file as a string, and interpolates the values of variables in it prior to returning a result. This means that the values stay as they were in the time the template was rendered. There are many approaches to the thing you want to achieve, the simplest one is to take an AJAX approach and continuously poll for new values.

Answer 2

That's because you're only reading them when the process starts instead of per request.

You could either:

a) retrieve them on every request (Eg. in the view, a context processor, etc..)

or

b) Ensure the module variables you're storing them in are updated whenever they change (Eg. using a post_save signal). This would, however, leave you open to unexpected behavior if you're ever running more than one process with one thread...