Difficulty in updating caching of official account web pages: How to avoid the old cache affecting the user experience after version update?

The official account web page update cache, this thing is simple and simple, and it is complicated enough to drink a pot of it.  You worked hard to update the official account article, but the user still opened the old version. Who can bear the taste?  In this article, let’s take a look at the twists and turns behind this and how to solve this problem gracefully. After reading it, you can easily deal with various caching problems, allowing your users to always experience the freshest content.

Tell me some basic things first. To put it bluntly, in order to improve access speed, the browser or server stores some static resources (such as pictures, CSS, JS) or page content. Next time you access it, you can directly retrieve it from the cache without having to download it again, and it is naturally fast. But this thing is also a double-edged sword. The new version is online, the old cache is still there, and the user still sees old content, which is embarrassing.

The core issue is how to effectively make the browser or server "forget" the old cache and reload the new version.  Among them, the cache header information in the HTTP protocol plays a key role.  Cache-Control and Expires are the key to controlling cache life and death.

Expires is relatively simple and crude, directly specify an expiration time.  However, this time is server time, and there may be differences between the user's local time, so the accuracy is not high.

Cache-Control is much more flexible. You can set max-age to specify the validity time (in seconds) of the cache, and you can also set instructions such as no-cache (force verification to the server every time), no-store (prohibit any cache) and other instructions.  Generally speaking, max-age can be effectively avoided by combining no-cache with a small enough value, or simply using

.

Cache-ControlLook at an example, use Python to simulate the settings

Header information:

from flask import Flask, make_response

app = Flask(__name__)

@app.route('/')
def index():
    response = make_response("Hello, World!")
    response.headers['Cache-Control'] = 'no-cache, no-store, must-revalidate'
    response.headers['Pragma'] = 'no-cache'
    response.headers['Expires'] = '0'
    return response

if __name__ == '__main__':
    app.run(debug=True)

no-cache This code uses the Flask framework to simulate a simple web service, forcing the browser not to cache the page.  no-store, must-revalidate, Pragma: no-cache, Expires: 0 These three instructions can basically ensure that the latest content is obtained every time you request.

is added for compatibility with old browsers.

Further ensure that the browser does not cache.  This is not simply adding a parameter, but only after understanding the HTTP caching mechanism can you write efficient code.

Of course, this is just the most basic solution. In actual applications, you may also need to consider more advanced technologies such as version number and file hash value.  For example, add a version number to the file name or URL, and change the file name every time you update, and the browser will automatically download the new file.  Or use the content hash value as part of the file name to ensure content consistency.

To go deeper, the use of CDN (content distribution network) is also a powerful tool to solve the caching problem.  CDN can cache your static resources to servers around the world, reducing user access latency and also more effectively controlling cache updates.  However, the configuration and management of CDNs are relatively complicated and require certain professional knowledge.

Finally, don't forget that code is just a tool, and it depends on ideas to solve problems.  When choosing a solution, you need to weigh performance, complexity, and maintenance costs.  Don't write hard-to-maintain code to pursue extreme performance.  Simplicity and effectiveness are the kingly way.  Remember, user experience is the most important thing.  A good solution should strike a balance between performance and user experience.

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