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Outbox pattern + Saga pattern(Choreography)

1. Architecture

2. Install(zookeeper, kafka)

  1. Download kafka

https://kafka.apache.org/downloads

  1. Start Zookeeper
bin/zookeeper-server-start.sh config/zookeeper.properties
  1. Start Kafka
bin/kafka-server-start.sh config/server.properties
  1. Create Topic
bin/kafka-topics.sh --create --bootstrap-server localhost:9092 --topic payment
bin/kafka-topics.sh --create --bootstrap-server localhost:9092 --topic payment.success
bin/kafka-topics.sh --create --bootstrap-server localhost:9092 --topic payment.dlt
bin/kafka-topics.sh --create --bootstrap-server localhost:9092 --topic payment.compensation

bin/kafka-topics.sh --create --bootstrap-server localhost:9092 --topic stock
bin/kafka-topics.sh --create --bootstrap-server localhost:9092 --topic stock.success
bin/kafka-topics.sh --create --bootstrap-server localhost:9092 --topic stock.dlt
bin/kafka-topics.sh --create --bootstrap-server localhost:9092 --topic stock.compensation

// check topic
bin/kafka-topics.sh --list --bootstrap-server localhost:9092
  1. Create Database
// Use same DB Instance.
create database orderdb;
create database stockdb;
create database paymentdb;
  1. Start Spring boot
order-service(8080)
stock-service(8081)
payment-service(8082)

3. Concern

1. What if I succeeded in publishing on Payment Topic but failed to publishing on Stock Topic?

answer: You need to roll back the message that went into the Payment Topic. And the data in the order_outbox table data should not be deleted. So I used "kafkaTemplate.executeInTransaction".

2. If multiple Springboot instances run a schedule, at some point two instances can send messages at the same time. What should I do in this case?

answer1: Use the leader selection feature to modify only one instance to be scheduled.

answer2: Add validation logic in the consumer(payment-service, stock-service), which conferences the published message.

3. How do I guarantee publish producer message?

answer: Record the storage time in the order_outbox table and publish it in order.

4. What if there is an exception in payment, stock service?

answer1: Blocking strategy

answer1: Non-Blocking strategy(DLQ)

4-1. What actions should I take in Order Service?

answer: Send a compensation request to StockService.

5. Compensation transactions based on each service status

order-service payment-service stock-service compensation
FAILED FAILED SUCCESS stock compensation
FAILED FAILED IN_PROGRESS -> SUCCESS self compensation(stock)
FAILED FAILED IN_PROGRESS -> FAILED X
FAILED SUCCESS FAILED payment compensation
FAILED IN_PROGRESS -> FAILED FAILED X
FAILED IN_PROGRESS -> SUCCESS FAILED self compensation(payment)
FAILED FAILED FAILED X
SUCCESS SUCCESS SUCCESS X