How to Cache Data with Python Flask

If you depending on a external source to return static data you can implement cachetools to cache data from preventing the overhead to make the request everytime you make a request to Flask.

This is useful when your upstream data does not change often. This is configurable with maxsize and ttl so whenever the first one's threshold is met, the application will fetch new data whenever the request has been made to your application.

Example

Let's build a basic flask application that will return the data from our data.txt file to the client:

from flask import Flask
from cachetools import cached, TTLCache

app = Flask(__name__)
cache = TTLCache(maxsize=100, ttl=60)

@cached(cache)
def read_data():
    data = open('data.txt', 'r').read()
    return data

@app.route('/')
def main():
    get_data = read_data()
    return get_data

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

Create the local file with some data:

$ touch data.txt
$ echo "version1" > data.txt

Start the server:

$ python app.py

Make the request:

$ curl http://localhost:5000/
version1

Change the data inside the file:

$ echo "version2" > data.txt

Make the request again:

$ curl http://localhost:5000/
version1

As the ttl is set to 60, wait for 60 seconds so that the item kan expire from the cache and try again:

$ curl http://localhost:5000/
version2

As you can see the cache expired and a new request has been made to read the file again and load it in cache, and then return to the client.

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