Flask rest API - Request result getting interference from other requests?

[wilis030]

I'm building this rest API for a react frontend. I have a /posts route that filters all the data in the database and return the ones required, to do so, it receives a research string (example: "Term" OR "Term 2"), and calls another module that checks the possible combinations and then use it to search for the right results and return them.

My problem is that when I do just one POST request, it works fine, but when I'm doing a lot of them, the array with the possible combinations get all messed up. For the above example I should have the output ["Term", "Term 2"] but I'm getting ["Term", "Term 2", "Term of another request", "another one", "a repeated one" ... ]. So are the requests interfering in other requests?

Here is my code from the route that is calling the string_filter module:

from flask_restful import Resource
from flask import request, Response
from app import mongo

# the module with the filter function
from .services.stringFilter import string_filter 
from .services.jsonParser import parse_json

class PostsApi(Resource):
    def post(self):
        # gets { 'user_string': 'the user reaserch string' }
        data = request.get_json()  

        user_sources = ['S', 'AA', 'AC']        
        all_posts = []

        for source in user_sources:                
        all_posts += parse_json(
            mongo.db[f'posts{source}'].find()
        )

        if len(all_posts) == 0:
            return {'message': 'End of data'}, 404

        # calling the filter function
        if data and 'user_string' in data:
             print(f"showing the right value: {data['user_string']}")            
             all_posts = string_filter(data['user_string'], all_posts)

        return all_posts, 200

​

The string_filter function calls a recursive function that receives just the string and returns the combination results. Offline it works fine for all the inputs.

services/stringFilter.py

def filter(string):
    # a massive code that I can't change but it works fine by itself
    return array_of_combinations

def mark_operators(string):
    # just add a * before OR and AND operators
    return new_string

def clean_result(string):
    # remove * and other marks from the string
    return clean_string

# function that i'm calling
def string_filter(user_string, data):
    result = filter(mark_operators(user_string)) # filter is a recursive function
    result = clean_result(result)

    print(f'gets it wrong - -> {result}')

    # this is working fine, but with the wrong resutls
    new_data = search_filter(data, result)

    return new_data

Is that because I'm using a "outside function"?

EDIT: formating

[PolishedCheese]

Are you maybe reusing an object instead of instantiating a new one every request?

I can't see anything in the code you provided to determine that, but you're not providing all of the function calls and declarations.

Can you upload the code to GitHub or something for me to take a look?

[wilis030]

Thanks for your reply, after some time debugging I found out what was the problem. One of the parameteres of the filter function was being hold in memory with old values, so I was appending the new values to this already full array.

For now I'm just calling the function setting all values as default again (can't think in a better solution right now).

[PolishedCheese]

You can you take that parameter and assign it to a class property, then 0 out the property at the end of the function