Implementing RPC client and server in RabbitMQ - Mini Project: Build & Apply

Implementing RPC client and server

📖 Scenario: You are building a simple Remote Procedure Call (RPC) system using RabbitMQ. This system allows a client to send a request to a server to calculate the square of a number. The server receives the request, processes it, and sends back the result.This is like ordering a coffee at a cafe: you tell the barista your order (request), they prepare it (process), and then give it back to you (response).

🎯 Goal: Build a basic RPC client and server using RabbitMQ in Python. The client will send a number, and the server will return the square of that number.

📋 What You'll Learn

Create a RabbitMQ connection and channel

Set up a queue for RPC requests

Implement the server to listen for requests and send back results

Implement the client to send requests and wait for responses

💡 Why This Matters

🌍 Real World

RPC systems are used in microservices to allow different services to communicate and request actions from each other asynchronously.

💼 Career

Understanding how to implement RPC with message brokers like RabbitMQ is valuable for backend developers and DevOps engineers working with distributed systems.

1

Setup RabbitMQ connection and declare RPC queue

Create a RabbitMQ connection using pika.BlockingConnection with default parameters. Then create a channel from this connection and declare a queue named rpc_queue with durable=True.

RabbitMQ

# Your code here

Need a hint?

Use pika.ConnectionParameters('localhost') to connect to RabbitMQ on your local machine.

2

Define the server callback to process RPC requests

Define a function called on_request that takes ch, method, props, and body as parameters. Inside, convert body to an integer, calculate its square, and publish the result back to the props.reply_to queue with the same correlation_id. Finally, acknowledge the message with ch.basic_ack.

RabbitMQ

import pika

connection = pika.BlockingConnection(pika.ConnectionParameters('localhost'))
channel = connection.channel()
channel.queue_declare(queue='rpc_queue', durable=True)

# Define the on_request callback function here
# Your code here

Need a hint?

Use props.reply_to to send the response back to the client queue.

3

Start consuming RPC requests on the server

Use channel.basic_qos(prefetch_count=1) to limit unacknowledged messages. Then use channel.basic_consume with queue='rpc_queue' and on_request as the callback. Finally, start consuming with channel.start_consuming().

RabbitMQ

import pika

connection = pika.BlockingConnection(pika.ConnectionParameters('localhost'))
channel = connection.channel()
channel.queue_declare(queue='rpc_queue', durable=True)

def on_request(ch, method, props, body):
    n = int(body)
    response = n * n

    ch.basic_publish(exchange='',
                     routing_key=props.reply_to,
                     properties=pika.BasicProperties(correlation_id=props.correlation_id),
                     body=str(response))
    ch.basic_ack(delivery_tag=method.delivery_tag)

# Set QoS and start consuming
# Your code here

Need a hint?

Use basic_qos to process one message at a time.

4

Implement the RPC client to send request and receive response

Create a class RpcClient with a constructor that connects to RabbitMQ and declares a unique callback queue. Implement a method call that sends a number as a request to rpc_queue with a unique correlation_id and waits for the response on the callback queue. Print the response received from the server for the number 7.

RabbitMQ

# Your code here

Need a hint?

Use uuid.uuid4() to generate a unique correlation ID.

Use process_data_events() to wait for the server response.