🌹 rosetrap: The Asynchronous Variable Data Hub

rosetrap provides an efficient, non-polling mechanism for inter-process communication (IPC) and variable synchronization across Python scripts, leveraging FastAPI on the server and the requests library on the client.

It implements a robust, event-driven pattern that allows a consuming process to block indefinitely without consuming CPU cycles until a producing process updates the required variable.

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✨ Key Features

• Asynchronous Blocking: Uses asyncio.Event on the FastAPI server to suspend client requests, eliminating busy-waiting and high CPU load typically associated with polling.
• Zero-Config IPC: No need for complex message queues (Redis, Kafka); state is managed centrally by the lightweight DATA_HUB.
• Deadlock Prevention: Robust client logic handles race conditions where data arrives between the initial status check and the blocking request.
• Simple API: Client-side functions are reduced to two clear commands: printToServer() (Write) and receiveFromServer() (Read/Block).
• Independent Variables: State management is fully independent for each variable name, allowing concurrent, synchronized access by multiple clients.

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🛠️ Installation & Setup

1. Install dependencies:

   pip install fastapi requests pydantic uvicorn

2. Start the Server: The server_data_hub.py script must be running first.

   python server_data_hub.py
   # Server runs on http://0.0.0.0:8000

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🚀 Usage Example: Concurrent Hand-off

This example demonstrates how Client A blocks waiting for Client C's data, and then how Client B blocks waiting for Client A's computed result, all without polling.

1. The Server and Core Utilities

Ensure server_data_hub.py and core_utils.py are in your project directory.

2. Client Scripts

Create these three files in the same directory:

client_A.py (Consumer of X, Producer of Y)

import time
from core_utils import receiveFromServer, printToServer, set_client_id

set_client_id("CLIENT A")

# 1. Block until 'X_Data' is ready
print("CLIENT A: Waiting to receive X_Data...")
x_data = receiveFromServer("X_Data", timeout_seconds=60)

if x_data:
    print(f"CLIENT A: Successfully received X_Data: {x_data}")
    
    # 2. Compute a new value 'Y_Data'
    time.sleep(1) # Simulate computation time
    y_data = str(int(x_data) * 2)
    print(f"CLIENT A: Calculated Y_Data = X_Data * 2 = {y_data}")

    # 3. Send the new value 'Y_Data'
    print("CLIENT A: Sending Y_Data...")
    printToServer("Y_Data", y_data)
    print("CLIENT A: Finished sending Y_Data.")
else:
    print("CLIENT A: Failed to receive X_Data.")

client_B.py (Final Consumer of Y)

from core_utils import receiveFromServer, set_client_id

set_client_id("CLIENT B")

# 1. Block until 'Y_Data' is ready
print("CLIENT B: Waiting to receive Y_Data...")
y_data = receiveFromServer("Y_Data", timeout_seconds=60)

if y_data:
    print(f"CLIENT B: Successfully received Y_Data: {y_data}")
    print("CLIENT B: Final result received. Execution complete.")
else:
    print("CLIENT B: Failed to receive Y_Data. Timeout or error occurred.")

client_C.py (Initial Producer of X)

import time
from core_utils import printToServer, set_client_id

set_client_id("CLIENT C")

# 1. Compute the initial value
initial_value = 50
time.sleep(4) # Simulate initial computation delay

# 2. Send the value 'X_Data'
print(f"CLIENT C: Computation finished. Sending X_Data: {initial_value}")
printToServer("X_Data", initial_value)
print("CLIENT C: Finished sending X_Data.")

3. Execution Sequence

The terminal output will clearly show the blocking and release mechanism.

1. Start Blocking Clients:

   python client_A.py &
   python client_B.py &

   Client A and B will print their "Waiting" messages and then immediately stop consuming CPU, as they are blocked on the server's asyncio.Event.wait().

2. Trigger the Chain:

   python client_C.py

Expected Flow:

1. Client C sends "50" for X_Data after a 4-second delay.
2. The Server sees the X_Data lookout is True (set by Client A) and signals the event.
3. Client A unblocks, receives "50", computes the result (100), and sends "100" for Y_Data.
4. The Server sees the Y_Data lookout is True (set by Client B) and signals the event.
5. Client B unblocks, receives "100", and finishes.