Cyberhaven Backend Engineer - Coding Problem

cyberhaven_interview_problem.py

import uuid

import flask 
# JSONRESPONSE


app = flask.Flask(__name__)



MAX_TIME = 10
START_PAIR_TIME = 0
PAIR_ID = None
NUM_PAIRS = 0

# use a multiprocessing memory manager
import multiprocessing
import queue
call_queue = multiprocessing.Queue()


def reset_globals():
    global PAIR_ID
    pair_id = PAIR_ID
    PAIR_ID = None
    return pair_id

import time


#atomic operation - mutexes and locks

import threading
lock = threading.Lock()

stats_dict = [0]*50000


@app.route("/join", methods=["POST"])
def join():
    # accept a POST Request with empty payload
    global PAIR_ID, START_PAIR_TIME

    with lock:
        if PAIR_ID:
            pair_id = reset_globals()
            call_queue.put(pair_id)
            NUM_PAIRS += 1
            if NUM_PAIRS < 50000:
                stats_dict[NUM_PAIRS] = (PAIR_ID, time.time()-START_PAIR_TIME)

            return pair_id+ "SECOND"

        # create a PAIR ID, You are FIRST
        PAIR_ID = str(uuid.uuid4())
        START_PAIR_TIME = time.time()

    # wait for 10 seconds for the second client to connect
    try:
        result_pair_id = call_queue.get(timeout=MAX_TIME)
        if result_pair_id:
            # we have second
            return result_pair_id+ "FIRST"
    except queue.Empty as e:
        reset_globals()
        return "Timeout. No More Connected Clients."


# Scenario: one client connects and times out. next client connects and the third client connnects. What happens? 


# stats endpoint
@app.route("/stats", methods=["GET"])
def stats():
    return stats_dict


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