Python async callback synchronization using queues

async_callback_queue_sync.py

import queue
import threading
import time
import uuid

# Create two queues: one for requests and one for responses
request_queue = queue.Queue()
response_queue = queue.Queue()

# Callback function that puts a request into the request queue and waits for the response
def async_callback():
    request_id = str(uuid.uuid4())  # Generate a unique request ID
    request = {"id": request_id, "data": "Request Data"}

    # Put the request into the request queue
    request_queue.put(request)
    print(f"Callback: Placed request {request_id} in the queue.")

    # Wait for the response
    while True:
        response = response_queue.get()
        if response["id"] == request_id:
            print(f"Callback: Received response for request {request_id}.")
            break

# Main thread that processes requests and places responses in the response queue
def main_thread(event):
    while not event.is_set():
        try:
            # Check for incoming requests
            request = request_queue.get(timeout=1)
            print(f"Main Thread: Processing request {request['id']}.")

            # Process the request (simulate with sleep)
            time.sleep(1)
            response = {"id": request["id"], "result": "Response Data"}

            # Place the result into the response queue
            response_queue.put(response)
            print(f"Main Thread: Placed response for request {request['id']} in the queue.")
        except queue.Empty:
            # Continue the normal function
            print("Main Thread: No incoming requests, continuing normal function.")
            time.sleep(1)

# Start the main thread
event = threading.Event()
thread = threading.Thread(target=main_thread, args=(event,), daemon=True)
thread.start()

# Simulate the asynchronous callback
for _ in range(3):
    async_callback()
    time.sleep(2)

time.sleep(3)
    
# Stop the main thread
event.set()
thread.join()