RabbitMQ Messaging & Async Systems · 课时

用于集群的联邦插件

探索联邦插件，在无需复杂网络配置的情况下，将多个 RabbitMQ 消息代理连接成逻辑集群。创建跨越多个数据中心的分布式消息系统。

第 3 / 4 课11 个步骤

用于集群的联邦插件 是 CoddyKit 上的免费 RabbitMQ Messaging & Async Systems 课时。这是第 3 节课，共 4 节。你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。这是 RabbitMQ Messaging & Async Systems 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 RabbitMQ Messaging & Async Systems 课程共包含 4 节课。

本课时的部分内容尚未翻译，以英文显示。

What is RabbitMQ Federation?

Imagine you have RabbitMQ brokers in different data centers or cloud regions. How do they share messages without complex network setups?

The Federation plugin allows you to loosely connect these brokers. It enables messages to flow between them, creating a distributed messaging system across geographical boundaries.

Federation vs. Traditional Clustering

It's important to distinguish Federation from traditional RabbitMQ clustering:

Clustering: Tightly couples nodes, sharing state and data. Best for high availability within a single, low-latency network (e.g., a data center).
Federation: Loosely connects brokers by replicating messages. Ideal for spanning wide area networks (WANs) or connecting brokers managed by different teams. It doesn't share state like a cluster.

Key Components: Upstreams & Policies

Federation relies on two main concepts:

Upstreams: These define the source broker from which messages will be pulled. An upstream specifies the connection details (like URI) of the remote RabbitMQ instance.
Policies: These rules determine which exchanges or queues on your downstream broker should connect to which upstream broker. They use regular expressions to match names.

Enabling the Federation Plugin

Before you can use federation, you need to enable the plugin on all participating RabbitMQ brokers. This is done using the RabbitMQ command-line tool.

Run this command on each broker:

rabbitmq-plugins enable rabbitmq_federation rabbitmq_federation_management

Configuring an Upstream Link

An 'upstream' tells your local broker where to pull messages from. You define it using the rabbitmqctl set_parameter command.

This example sets up an upstream named 'my-upstream' pointing to a remote broker:

rabbitmqctl set_parameter federation-upstream my-upstream \
'{"uri":"amqp://guest:guest@remote-host:5672","expires":3600000}'

Creating a Federation Policy for Exchanges

Once an upstream is defined, you apply it to exchanges using a policy. This policy tells your local broker to federate messages for matching exchanges from the specified upstream.

This policy federates all exchanges starting with 'fed.' from 'my-upstream':

rabbitmqctl set_policy --apply-to exchanges \
fed-exchanges ".^fed\\..*" \
'{"federation-upstream":"my-upstream"}'

How Federated Exchanges Work

With a federated exchange:

A producer publishes messages to an exchange on the upstream broker.
The federation plugin on the downstream broker pulls these messages from the upstream exchange.
The messages then arrive at the corresponding federated exchange on the downstream broker, where local consumers can receive them.

The consumer only interacts with its local (downstream) broker.

Client Example: Consuming from Federated Exchange

Here's a Python consumer that connects to a downstream broker and receives messages from a federated exchange. It doesn't need to know the messages originated from an upstream broker.

To run this, ensure you have pika installed (pip install pika).

import pika
import sys
import os

def main():
    # Connect to the local (downstream) RabbitMQ broker
    connection = pika.BlockingConnection(pika.ConnectionParameters('localhost'))
    channel = connection.channel()

    # Declare the exchange that is federated from an upstream broker
    # (e.g., using the policy created in previous steps for 'fed_logs')
    channel.exchange_declare(exchange='fed_logs', exchange_type='fanout', durable=True)

    result = channel.queue_declare(queue='', exclusive=True)
    queue_name = result.method.queue

    channel.queue_bind(exchange='fed_logs', queue=queue_name)

    print(' [*] Waiting for federated messages. To exit press CTRL+C')

    def callback(ch, method, properties, body):
        print(f" [x] Received: {body.decode()}")

    channel.basic_consume(queue=queue_name, on_message_callback=callback, auto_ack=True)
    channel.start_consuming()

if __name__ == '__main__':
    try:
        main()
    except KeyboardInterrupt:
        print(' Interrupted')
        try:
            sys.exit(0)
        except SystemExit:
            os._exit(0)

Federating Queues

You can also federate queues. When a queue is federated, messages published to that queue on the upstream broker will be pulled and added to the corresponding queue on the downstream broker.

The policy setup is very similar, just specify --apply-to queues:

rabbitmqctl set_policy --apply-to queues \
fed-queues ".^fed\\..*" \
'{"federation-upstream":"my-upstream"}'

Quick Check on Federation

Which of the following best describes the primary use case for RabbitMQ Federation?

在交互式课程中回答

Recap: Federation for Distributed Messaging

In this lesson, you learned about the RabbitMQ Federation plugin:

It allows you to connect RabbitMQ brokers across different locations.
It uses upstreams to define source brokers and policies to apply federation rules.
Federation differs from clustering by offering loose coupling, suitable for WANs.
You can federate both exchanges and queues, enabling flexible message distribution in a distributed system.

This powerful plugin helps you build robust, geographically distributed messaging architectures.

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常见问题解答

「用于集群的联邦插件」课时是免费的吗？

是的 — 「用于集群的联邦插件」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 RabbitMQ Messaging & Async Systems 课程的其余内容，请升级到 CoddyKit PRO。 RabbitMQ Messaging & Async Systems 课程共包含 4 节课。

「用于集群的联邦插件」这节课中我会学到什么？

探索联邦插件，在无需复杂网络配置的情况下，将多个 RabbitMQ 消息代理连接成逻辑集群。创建跨越多个数据中心的分布式消息系统。你通过在浏览器中直接运行的动手代码来练习 RabbitMQ Messaging & Async Systems，全天候 AI 导师会在你学习这节课的过程中回答你的问题。

学习 RabbitMQ Messaging & Async Systems 需要有经验吗？

无需任何先前经验。CoddyKit 上的 RabbitMQ Messaging & Async Systems 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。这是第 3 节课，共 4 节。

「用于集群的联邦插件」课时需要多长时间？

大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。

我能在这节 RabbitMQ Messaging & Async Systems 课中编写并运行代码吗？

能。每节 RabbitMQ Messaging & Async Systems 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。

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