Task-Xromzo

The code assignment.

STEP 1: Design an ObjectMgr which manages a pool of objects. Objects can be considered to be ints (from 1 to n). It should provide api’s to get_object() and free_object():

get_object(): Returns any object available in the pool. An object cannot be given away again unless it has been freed. free_object(int obj): Returns the object back to the pool so that it can be given out again.

Please document the API’s definitions, data structures and write tests.

STEP 2:

1. Write a GraphQL API schema to use the above functions to create, get and free objects.
2. Deploy it as a service/container that can be used to deploy on a linux server.

Answer

In .app/object/objectmgr.py, created class ObjectMgr.

from collections import deque
from typing import Union

class ObjectMgr:
    def __init__(self, n: int):
        self.object_pool = deque(range(1, n))
        self.allocated_objects = set()
        self.freed_objects = deque()

Decided to use:

• deque() - efficient element addition and removal.

    def get_object(self) -> Union[int, None]:
        if self.object_pool:
            obj = self.object_pool.popleft()
            self.allocated_objects.add(obj)
            return obj
        elif self.freed_objects:
            obj = self.freed_objects.popleft()
            self.allocated_objects.add(obj)
            return obj
        else:
            return None

• set() - efficient to check whether an object is currently allocated or not.

    def free_object(self, obj) -> Union[int, None]:
        if obj in self.allocated_objects:
            self.allocated_objects.remove(obj)
            self.freed_objects.append(obj)
            return obj
        else:
            raise ValueError("Object is not currently allocated.")

Installation

• Development

0. Make sure your python is <= "3.10.*"

1. Create virtual env, with:

python -m venv .venv

2. move to app folder'

cd ./app

3. Install requirements with pip:

pip install -r requirements.txt

4. Or install requirements with poetry:

poetry install

3. To run app:

flask run

flask --debug run

python app.py

gunicorn --worker-class gevent --workers 8 --bind 127.0.0.1:5000 app:"create_app()" --max-requests 10000 --timeout 5 --keep-alive 5 --log-level info --log-level info

• To run with docker-compose

1. create docker-compose.yml from:

   • docker-compose.dev.yml
   • or
   • docker-compose.prod.yml

2. run

   docker-compose up

Production

To run application as linux service

• create /etc/systemd/system/tromzo-service.service

[Unit]
Description=Gunicorn instance to serve
After=network.target

[Service]
User=mngr-user
Group=www-data
WorkingDirectory=/home/tromzo/app
Environment="PATH=/home/tromzo/app/.venv/bin"
ExecStart=/home/tromzo/app/.venv/bin gunicorn --worker-class gevent --workers 8 --bind 0.0.0.0:3000 app:"create_app()" --max-requests 10000 --timeout 5 --keep-alive 5 --log-level info

[Install]
WantedBy=multi-user.target

sudo systemctl start tromzo-service
sudo systemctl enable tromzo-service

To run application as container

docker run --publish 3000:3000 -it --entrypoint ./start.sh objmngr-server/graphql

config

• in config.py if

default = "DevelopmentConfig"

• visit {your_host}/graphql to see/test API definitions

Query examples:

get_object() query:

Returns any object available in the pool

query {
  getObject
}

free_object() mutation:

Returns the object back to the pool so that it can be given out again

mutation {
    freeObject(obj: 1) {
        success
    }
}

postman_collection.json is available

Tests

• To run tests

pytest

p.s They liked the solution and I was moved to the next step.