Overengineer - resources manager

gistfile1.txt

import time
import sqlite3
import os.path

RESOURCE_TIME_LIMIT = 100


db_path = os.path.dirname(os.path.realpath(__file__)) + '/resources.db'


def request_resource(resource_name, request_uuid, retries=5):
    resource_value = _request_for(resource_name, request_uuid)
    if _confirm_resource(request_uuid):
        return resource_value
    else:
        if retries == 0:
            time.sleep(0.5)
            retries -= 1
            return request_resource(resource_name)
    raise Exception('Failed to get a resource - Timeout')


def release_resource(request_uuid):
    conn = sqlite3.connect(db_path)
    db = conn.cursor()

    sql_update = "UPDATE resources SET uuid = '' WHERE uuid = ?"
    db.execute(sql_update, (str(request_uuid), ))

    conn.commit()
    conn.close()


class Singleton(type):
    def __init__(cls, name, bases, attrs, **kwargs):
        super().__init__(name, bases, attrs)
        cls._instance = None

    def __call__(cls, *args, **kwargs):
        if cls._instance is None:
            cls._instance = super().__call__(*args, **kwargs)
        return cls._instance


def _confirm_resource(request_uuid):
    conn = sqlite3.connect(db_path)
    db = conn.cursor()

    sql_select = "select * from resources where uuid = ?"
    result = db.execute(sql_select, (str(request_uuid),)).fetchall()
    conn.close()

    if not result:
        return False
    return True


def _request_for(resource_name, request_uuid):
    conn = sqlite3.connect(db_path)
    db = conn.cursor()

    sql_select = "select * from resources where resource_name == ? and uuid == '' limit 1"
    resource = db.execute(sql_select, (resource_name,)).fetchall()

    sql_update = "UPDATE resources SET uuid = ? WHERE id = ?"
    db.execute(sql_update, (request_uuid, resource[0][0], ))
    conn.commit()
    conn.close()
    return resource[0][2] # resource_value


class ResourceManager(metaclass=Singleton):
    def __init__(self):
        if create_db():
            setup_resource_manager_db()


def create_db():
    try:
        conn = sqlite3.connect(db_path)
        db = conn.cursor()
        db.execute(
            "CREATE TABLE resources(id INTEGER PRIMARY KEY, resource_name TEXT, resource_value TEXT, uuid TEXT, lock_time_stamp REAL)")
        conn.commit()
        conn.close()
    except:
        return False
    return True


def setup_resource_manager_db():
    conn = sqlite3.connect(db_path)
    try:
        db = conn.cursor()
        db.execute("INSERT INTO resources(resource_name, resource_value, uuid, lock_time_stamp) VALUES ('client_id', 'integrated_tests0' , '', '');")
        db.execute("INSERT INTO resources(resource_name, resource_value, uuid, lock_time_stamp) VALUES ('client_id', 'integrated_tests1' , '', '');")
        db.execute("INSERT INTO resources(resource_name, resource_value, uuid, lock_time_stamp) VALUES ('client_id', 'integrated_tests2' , '', '');")
        db.execute("INSERT INTO resources(resource_name, resource_value, uuid, lock_time_stamp) VALUES ('client_id', 'integrated_tests3' , '', '');")
        db.execute("INSERT INTO resources(resource_name, resource_value, uuid, lock_time_stamp) VALUES ('client_id', 'integrated_tests4' , '', '');")
        db.execute("INSERT INTO resources(resource_name, resource_value, uuid, lock_time_stamp) VALUES ('client_id', 'integrated_tests5' , '', '');")
        db.execute("INSERT INTO resources(resource_name, resource_value, uuid, lock_time_stamp) VALUES ('client_id', 'integrated_tests6' , '', '');")
        db.execute("INSERT INTO resources(resource_name, resource_value, uuid, lock_time_stamp) VALUES ('client_id', 'integrated_tests7' , '', '');")
        db.execute("INSERT INTO resources(resource_name, resource_value, uuid, lock_time_stamp) VALUES ('client_id', 'integrated_tests8' , '', '');")
        db.execute("INSERT INTO resources(resource_name, resource_value, uuid, lock_time_stamp) VALUES ('client_id', 'integrated_tests9' , '', '');")
    except sqlite3.OperationalError:
        pass
    conn.commit()
    conn.close()