2nd/10_Wiki/Topic_Programming/Architecture/Choreography.md

id, title, category, status, canonical_id, aliases, duplicate_of, source_trust_level, confidence_score, verification_status, tags, raw_sources, last_reinforced, github_commit, tech_stack

id	title	category	status	canonical_id	aliases	duplicate_of	source_trust_level	confidence_score	verification_status	tags	raw_sources	last_reinforced	github_commit	tech_stack
wiki-2026-0508-choreography	Choreography	10_Wiki/Topics	verified	self	Event Choreography Saga Choreography	none	A	0.9	applied	microservices distributed-systems events saga		2026-05-10	pending	language framework typescript kafka-temporal

Choreography

매 한 줄

"매 service 가 자기 part 의 dance step 을 알고 events 으로 react — 매 central conductor 없음.". Choreography는 distributed workflow를 events 의 emit/subscribe 로 구현하는 pattern. Orchestration 의 반대 — 매 decoupling 매 high, 매 visibility 매 low. 2026년 event-driven microservices, EDA, Saga pattern 의 핵심 선택지.

매 핵심

매 Choreography vs Orchestration

측면	Choreography	Orchestration
Control	Distributed	Centralized (orchestrator)
Coupling	Low (events)	Higher (orchestrator knows all)
Visibility	Hard (trace tools 필요)	Easy (one workflow definition)
Add new step	Just subscribe	Edit orchestrator
Failure handling	Each service handles own	Orchestrator decides
Examples	Kafka events, NATS	Temporal, AWS Step Functions

매 패턴 종류

• Event-carried state transfer: event 가 모든 필요 data 포함.
• Event notification: event 는 trigger only, state 는 query.
• Saga choreography: distributed transaction 의 compensating events.

매 응용

1. E-commerce order flow (OrderCreated → Payment → Shipping events).
2. User signup pipeline (UserRegistered → emails → analytics).
3. IoT event processing (sensor → multiple consumers).
4. Domain events (DDD bounded context integration).

💻 패턴

Saga choreography (TypeScript + Kafka)

// Order service
async function createOrder(req: CreateOrderRequest) {
  const order = await db.orders.insert({ ...req, status: 'pending' });
  await kafka.produce('order.created', {
    orderId: order.id,
    userId: order.userId,
    amount: order.total,
  });
  return order;
}

// Order service also listens for compensations
kafka.consume('payment.failed', async (evt) => {
  await db.orders.update(evt.orderId, { status: 'cancelled' });
  await kafka.produce('order.cancelled', { orderId: evt.orderId });
});

Payment service reacts independently

kafka.consume('order.created', async (evt) => {
  try {
    const charge = await stripe.charges.create({
      amount: evt.amount * 100,
      customer: evt.userId,
    });
    await kafka.produce('payment.succeeded', {
      orderId: evt.orderId,
      chargeId: charge.id,
    });
  } catch (err) {
    await kafka.produce('payment.failed', {
      orderId: evt.orderId,
      reason: String(err),
    });
  }
});

Shipping service

kafka.consume('payment.succeeded', async (evt) => {
  const shipment = await shippingApi.create({ orderId: evt.orderId });
  await kafka.produce('shipment.created', { ...shipment });
});

Event schema (Avro / JSON Schema)

{
  "type": "record",
  "name": "OrderCreated",
  "fields": [
    { "name": "orderId", "type": "string" },
    { "name": "userId", "type": "string" },
    { "name": "amount", "type": "double" },
    { "name": "createdAt", "type": "string" }
  ]
}

Idempotent consumer

async function handleOrderCreated(evt: OrderCreated) {
  // Dedup by event id
  const seen = await redis.set(
    `processed:${evt.eventId}`,
    '1',
    { NX: true, EX: 86400 },
  );
  if (!seen) return; // already processed

  await processOrder(evt);
}

Distributed tracing (OTel) 매 visibility 회복

import { trace, context, propagation } from '@opentelemetry/api';

async function publishWithTrace(topic: string, evt: any) {
  const span = trace.getActiveSpan();
  const carrier: Record<string, string> = {};
  propagation.inject(context.active(), carrier);
  await kafka.produce(topic, {
    ...evt,
    _trace: carrier,
  });
}

매 결정 기준

상황	Approach
Simple linear workflow	Orchestration (Temporal)
Many independent reactors	Choreography
Strong consistency 필요	Orchestration + 2PC 또는 Temporal
Fan-out events	Choreography
Need visual workflow + retry	Orchestration
Event-driven domain (DDD)	Choreography

기본값: 매 simple 2-3 step domain workflow → orchestration (Temporal). 매 broad fan-out + autonomous teams → choreography.

🔗 Graph

• 부모: Event-Driven Architecture · Microservices
• 변형: Pub-Sub
• 응용: Broker Topology · Event Sourcing
• Adjacent: Orchestration · CQRS

🤖 LLM 활용

언제: event-driven microservice design, decoupling teams, fan-out workflows, autonomous services. 언제 X: short transactional flow needing visibility, strict ordering 필요한 critical financial workflows (orchestrator + Temporal 가 better).

❌ 안티패턴

• Distributed monolith via events: events 가 actually RPC 호출 — coupling 그대로.
• No event versioning: schema 변경 시 모든 consumer 깨짐 — Schema Registry 필수.
• Lost trace: span 이 event boundary 에서 끊김 — propagation injection 필수.
• Implicit ordering assumption: 매 services 가 임의 order 로 react — explicit ordering 필요 시 partition key.

🧪 검증 / 중복

• Verified (Hohpe "Enterprise Integration Patterns" / Microservices.io / Confluent docs 2026).
• 신뢰도 A.

🕓 Changelog

날짜	변경
2026-05-08	Phase 1
2026-05-10	Manual cleanup — Saga choreography + Kafka + OTel 패턴