docs(10_Wiki): Topic_Business/General/Graphic/Programming을 Topics/ 하위로 이동
최상위 10_Wiki/Topic_*였던 4개 카테고리 폴더를 10_Wiki/Topics/Topic_* 로 재배치. 콘텐츠 변경 없음(순수 폴더 이동) — Topics/ 하위 나머지 폴더는 이미 지난 커밋에서 전부 정리된 상태(잔존 항목은 에이전트 운영 상태 및 사용자가 보존을 요청한 업데이트0615/무제 3.canvas 뿐).
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Antigravity Agent
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---
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id: wiki-2026-0508-message-broker
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title: Message Broker
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category: 10_Wiki/Topics
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status: verified
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canonical_id: self
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aliases: [Message Brokers, MQ, Event Broker, Pub-Sub Broker]
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duplicate_of: none
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source_trust_level: A
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confidence_score: 0.9
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verification_status: applied
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tags: [messaging, distributed, kafka, rabbitmq, nats]
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raw_sources: []
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last_reinforced: 2026-05-10
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github_commit: pending
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tech_stack:
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language: multi
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framework: kafka-rabbitmq-nats
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---
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# Message Broker
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## 매 한 줄
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> **"매 producer 와 consumer 사이의 매 async middleman."**. Message broker 는 매 service 간 매 decouple, 매 buffering, 매 fan-out 을 제공하는 매 infrastructure. 매 2026 의 big three 는 매 Kafka (event streaming), 매 RabbitMQ (traditional queue), 매 NATS (lightweight low-latency). 매 cloud-native 는 SQS / Pub/Sub / EventBridge 도 매 흔함.
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## 매 핵심
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### 매 왜 broker
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- **Decoupling**: producer 가 consumer 의 위치/존재 모름.
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- **Buffering**: spike 흡수 — consumer 가 천천히 처리.
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- **Fan-out**: 1 message → N consumer.
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- **Reliability**: persistent queue → consumer crash 후 replay.
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- **Async**: producer 가 response 안 기다림.
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### 매 model
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- **Queue (point-to-point)**: 1 message → 1 consumer (load balance).
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- **Pub/Sub (topic)**: 1 message → N subscriber (broadcast).
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- **Event log**: 매 immutable append-only — replay/time-travel (Kafka).
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### 매 보장
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- **At-most-once**: 매 fast, 매 loss 가능.
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- **At-least-once**: 매 default, 매 duplicate 가능 → idempotent consumer 필요.
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- **Exactly-once**: 매 어렵 (Kafka EoS transactions, idempotent producer + transactional consumer).
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### 매 Kafka 핵심
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- **Topic** → **Partition** (parallelism unit) → **Offset**.
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- 매 Consumer group 으로 partition load balance.
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- 매 retention (time / size) — log 그대로 저장.
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- 매 replay 가능 — offset reset.
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### 매 RabbitMQ 핵심
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- **Exchange** (direct/topic/fanout/headers) → **Binding** → **Queue**.
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- 매 AMQP 0.9.1 (현재) / AMQP 1.0 / MQTT / STOMP.
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- 매 ack/nack, dead-letter exchange.
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- 매 message TTL, priority queue.
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### 매 NATS 핵심
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- 매 lightweight, sub-ms latency.
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- 매 Core NATS (fire-and-forget) + JetStream (persistence + at-least-once).
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- 매 subject hierarchy: `orders.eu.de`.
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## 💻 패턴
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### Kafka producer/consumer (Node.js, kafkajs)
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```javascript
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import { Kafka } from 'kafkajs';
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const kafka = new Kafka({ brokers: ['kafka:9092'], clientId: 'orders-svc' });
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// Producer
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const producer = kafka.producer({ idempotent: true }); // exactly-once-ish
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await producer.connect();
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await producer.send({
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topic: 'orders',
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messages: [{
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key: order.userId, // partition key → ordering per user
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value: JSON.stringify(order),
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}],
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});
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// Consumer
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const consumer = kafka.consumer({ groupId: 'fulfillment' });
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await consumer.subscribe({ topic: 'orders', fromBeginning: false });
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await consumer.run({
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eachMessage: async ({ message }) => {
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const order = JSON.parse(message.value.toString());
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await fulfill(order); // must be idempotent
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},
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});
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```
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### RabbitMQ (Node.js, amqplib)
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```javascript
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import amqp from 'amqplib';
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const conn = await amqp.connect('amqp://localhost');
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const ch = await conn.createChannel();
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// Topic exchange + DLX
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await ch.assertExchange('orders', 'topic', { durable: true });
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await ch.assertQueue('fulfillment', {
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durable: true,
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deadLetterExchange: 'orders.dlx',
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});
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await ch.bindQueue('fulfillment', 'orders', 'order.created.*');
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// Publish
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ch.publish('orders', 'order.created.eu', Buffer.from(JSON.stringify(order)),
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{ persistent: true });
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// Consume with manual ack
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ch.consume('fulfillment', async (msg) => {
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try {
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await fulfill(JSON.parse(msg.content.toString()));
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ch.ack(msg);
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} catch (e) {
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ch.nack(msg, false, false); // → DLX
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}
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}, { noAck: false });
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```
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### NATS JetStream (Node.js)
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```javascript
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import { connect, JSONCodec } from 'nats';
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const nc = await connect({ servers: 'nats://localhost:4222' });
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const js = nc.jetstream();
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const jc = JSONCodec();
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// Producer
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await js.publish('orders.created.eu', jc.encode(order));
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// Durable consumer
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const sub = await js.subscribe('orders.>', {
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config: { durable_name: 'fulfillment', ack_policy: 'explicit' },
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});
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for await (const m of sub) {
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await fulfill(jc.decode(m.data));
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m.ack();
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}
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```
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### Idempotent consumer (deduplication)
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```javascript
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async function handleMessage(msg) {
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const id = msg.headers['message-id'];
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// Try insert into processed table — unique constraint on id
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const inserted = await db.query(
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'INSERT INTO processed (id, ts) VALUES ($1, NOW()) ON CONFLICT DO NOTHING',
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[id]
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);
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if (inserted.rowCount === 0) return; // already processed
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await businessLogic(msg);
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}
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```
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### Outbox pattern (transactional publish)
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```sql
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-- Same DB transaction: write business state + outbox entry
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BEGIN;
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UPDATE orders SET status='paid' WHERE id=$1;
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INSERT INTO outbox (topic, payload, ts) VALUES ('orders.paid', $2, NOW());
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COMMIT;
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-- Separate process: poll outbox → publish to broker → mark sent
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```
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## 매 결정 기준
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| 상황 | Broker |
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|---|---|
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| Event streaming, replay, analytics | Kafka |
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| Complex routing, traditional queue | RabbitMQ |
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| Sub-ms latency, microservices | NATS |
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| AWS-native, simple | SQS + SNS |
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| GCP-native | Pub/Sub |
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| Azure-native | Service Bus / Event Hubs |
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| Single-process / dev | Redis Streams, in-memory |
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**기본값**: 매 cloud-native team → managed (SQS/Pub-Sub). 매 self-host + event log → Kafka. 매 traditional queue → RabbitMQ.
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## 🔗 Graph
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- 부모: [[Distributed Systems]] · [[Event-Driven Architecture]]
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- 변형: [[Kafka]] · [[RabbitMQ]] · [[NATS]] · [[SQS]] · [[Pub-Sub]]
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- 응용: [[Microservices]] · [[Event Sourcing]] · [[CQRS]]
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- Adjacent: [[Message-Queues-and-Event-Streams]] · [[Dead Letter Queue]]
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## 🤖 LLM 활용
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**언제**: service decoupling, async workflow, event-driven design, spike absorption.
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**언제 X**: 매 simple sync RPC 면 충분 — 매 broker = operational overhead.
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## ❌ 안티패턴
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- **At-most-once 로 critical data**: 매 loss 허용 안되면 매 ack 필수.
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- **No idempotency**: 매 at-least-once 에서 매 duplicate → side effect 2번.
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- **Big payload**: 매 broker 에 large blob → 매 S3 reference 패턴 사용.
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- **No DLQ**: 매 poison message 가 매 무한 retry → consumer 마비.
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- **Kafka 를 queue 로**: 매 ordering 만 필요한 매 short job → RabbitMQ 가 더 적합.
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## 🧪 검증 / 중복
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- Verified (Apache Kafka docs, RabbitMQ docs, NATS docs, Confluent blog, Microservices.io patterns).
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- 신뢰도 A.
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## 🕓 Changelog
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| 날짜 | 변경 |
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|---|---|
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| 2026-05-08 | Phase 1 |
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| 2026-05-10 | Manual cleanup — Kafka/RabbitMQ/NATS 비교 + outbox/idempotent 패턴 |
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