Saga Orchestration Framework writing for provide transactions in the Spring Boot Microserviceds. We know for transaction monolithic application working as ACID principe but, at the microservice architecture does not work it's concept. What is ACID? ACID is abviature, to use in Relational Database Management System for manage transactions.
- Atomic: results of a transaction are seen entirely or not at all within other transactions. (A transaction need not appear atomic to itself.)
- Consistent: system-defined consistency constraints are enforced on the results of transactions. (Not going to discuss constraint checking today.)
- Isolated: transactions are not affected by the behavior of concurrently-running transactions.
- Durable: once a transaction commits, its results will not be lost regardless of subsequent failures.
Microservice architecture has each application it's databases. Our business logic everything does not work only one microservice and sometimes your a business logic must to work more than two microservices. That situation doesn't work ACID concept to whole business logic and in the database will be to full up with doesn't finished data. For this will use saga orchestration design pattern for distributed transactions. In details about it click this is link.
This is framework to conversation microservice used Apache Kafka api and each event state save in the Redis to finish saga.
- Getting started
- Saga tools
- @SagaAssociateId
- @SagaOrchestration
- @SagaOrchestEventHandler
- @SagaOrchestStart
- @SagaOrchestEnd
- @SagaOrchestException
- SagaGateway
1.You must add each microservice pom.xml its dependency:
<dependency>
<groupId>io.github.dilsh0d</groupId>
<artifactId>spring-microservice-saga</artifactId>
<version>0.0.6</version>
</dependency>
- Declaration @EnableSagaOrchestration microservice in the starter app class. This annotation auto configure Kafka and Redis client connection. example from project
@EnableSagaOrchestration
@EnableEurekaClient
@SpringBootApplication
public class OrderServiceApplication {
public static void main(String[] args) {
SpringApplication.run(OrderServiceApplication.class, args);
}
}- application.properties or application.yml file add this configuration example from project
kafka:
producer:
transaction-id-prefix: saga_pattern_event
client-id: events_producer
key-serializer: org.apache.kafka.common.serialization.StringSerializer
value-serializer: org.springframework.kafka.support.serializer.JsonSerializer
bootstrap-servers: localhost:9092
consumer:
groupid: saga_pattern_order_event
client-id: events_order_consumer
auto-offset-reset: earliest
bootstrap-servers: localhost:9092
max-poll-records: 1
redis:
host: localhost
port: 6379 That all we configured all things from three steps.
Next step we look at the framework 6 annotation tools which of what does is its.
| Annotations | Descreption |
|---|---|
@SagaAssociateId |
Saga associate will save in redis or get from redis. |
@SagaOrchestration |
Declaration only above saga class. |
@SagaOrchestEventHandler |
Declaration only above event hanler methods in the saga class |
@SagaOrchestStart |
Declaration with @SagaOrchestEventHandler event handler methods, that is meant saga class started with method. |
@SagaOrchestEnd |
Declaration with @SagaOrchestEventHandler event handler methods, that is meant saga class ended with method |
@SagaOrchestException |
Declaration in the saga class exception handlers |
Annotation declaration saga instances event class unique id field and after start saga from this id to store use this id saga instance to redis and next actions for use as (associate Id). You can declaration other need fields but don't forget create get/set methods so as doesn't parse in the save to rides.
@Getter
@Setter
public class CreateOrderEvent {
@SagaAssociateId
private String id;
private List<Integer> items;
}Declaration on the class where distributed transaction management between microservice and this is annotation create Spring bean with scope prototype. If saga class will work with @SagaOrchestStart event handler then create spring instance else get by associate id from redis this object and create instance from this. Each come event to Saga class @SagaOrchestEventHandler method save to redis by associateId. If Event handler method declaration with annotation @SagaOrchestEnd then Saga Instance to finished its work and remove from redis by associate id. Saga class is to declare @SagaOrchestException so as we can catch exceptions and run rollback() events.
- Saga class declaration primitive and reference types you must create get/set methods else will be json parse exceptions.
- Saga class declaration spring bean fields must before add keyword transient and bean does not need create get/set method.
@SagaOrchestration
public class OrderSaga {
private String orderId;
private String paymentId;
private PaymentType paymentType;
private BigDecimal amount = new BigDecimal("20.5");
private List<Integer> itemsId;
public String getOrderId() {
return orderId;
}
public void setOrderId(String orderId) {
this.orderId = orderId;
}
public String getPaymentId() {
return paymentId;
}
public void setPaymentId(String paymentId) {
this.paymentId = paymentId;
}
public PaymentType getPaymentType() {
return paymentType;
}
public void setPaymentType(PaymentType paymentType) {
this.paymentType = paymentType;
}
public BigDecimal getAmount() {
return amount;
}
public void setAmount(BigDecimal amount) {
this.amount = amount;
}
public List<Integer> getItemsId() {
return itemsId;
}
public void setItemsId(List<Integer> itemsId) {
this.itemsId = itemsId;
}
@Autowired
private transient SagaGateway sagaGateway;
@Autowired
private transient OrderPushNotification orderPushNotification;
@Autowired
private transient OrderService orderService;
@SagaOrchestStart
@SagaOrchestEventHandler
public void handler(CreateOrderEvent event){
this.orderId = event.getId();
this.itemsId = event.getItems();
orderService.createOrder(event, amount);
orderPushNotification.sentClientNotification(event.getId(),
"YOUR ORDER CREATED, PLEASE SELECT PAYMENT TYPE AND PAY FROM IT : [ " + PaymentType.getStrings()+" ]");
}
@SagaOrchestEventHandler
public void handler(ChooseOrderPaymentTypeEvent event) {
if (paymentId == null) {
CreateReceiptPaymentEvent createReceiptPaymentEvent = new CreateReceiptPaymentEvent();
createReceiptPaymentEvent.setId(UUID.randomUUID().toString());
createReceiptPaymentEvent.setOrderId(orderId);
createReceiptPaymentEvent.setPaymentType(event.getPaymentType());
createReceiptPaymentEvent.setAmount(amount);
sagaGateway.send(createReceiptPaymentEvent);
} else {
TryAgainReceiptPaymentEvent againReceiptPaymentEvent = new TryAgainReceiptPaymentEvent();
againReceiptPaymentEvent.setId(paymentId);
againReceiptPaymentEvent.setPaymentType(event.getPaymentType());
sagaGateway.send(againReceiptPaymentEvent);
}
}
@SagaOrchestEventHandler
public void handler(OrderPaymentEntityCreatedEvent event) {
this.paymentId = event.getPaymentId();
this.paymentType = event.getPaymentType();
orderService.updateOrder(event);
orderPushNotification.sentClientNotification(event.getId(), "PAYMENT ID:[ " + paymentId + " ] "
+ paymentType.name() + " SUCCESSFUL SELECTED. YOU CAN PAY FROM IT'S PAYMENT TYPE");
}
@SagaOrchestEnd
@SagaOrchestEventHandler
public void handler(SuccessOrderEvent event) {
orderService.orderSuccessfulPaymentDone(event);
orderPushNotification.sentClientNotification(event.getId(), "ORDER SUCCESSFUL PAYMENT DONE.");
}
@SagaOrchestEnd
@SagaOrchestEventHandler
public void handler(RollbackOrderEvent event) {
orderService.orderProcessFail(event);
if(!event.isCallPaymentSaga()) {
RollbackPaymentEvent rollbackPaymentEvent = new RollbackPaymentEvent();
rollbackPaymentEvent.setId(paymentId);
rollbackPaymentEvent.setCallOrderSaga(true);
sagaGateway.send(rollbackPaymentEvent);
}
orderPushNotification.sentClientNotification(event.getId(), "ORDER PROCESS FAIL AND ROLLBACK");
}
@SagaOrchestException
public void exceptionHandler(SagaExceptionHandler sagaExceptionHandler){
orderPushNotification.sentClientNotification(sagaExceptionHandler.getSagaId(),
"ORDER EXCEPTION IN EVENT CLASS"+sagaExceptionHandler.getExceptionEventClass()
+" SAGA METHOD NAME "+ sagaExceptionHandler.getExceptionSagaMethodName()
+"EXCEPTION MESSAGE :["+sagaExceptionHandler.getException().getMessage()+"]");
RollbackOrderEvent rollbackOrderEvent = new RollbackOrderEvent();
rollbackOrderEvent.setId(orderId);
sagaGateway.send(rollbackOrderEvent);
}
}Declaration with annotation method will be handle from sent sagaGateway bean events.
1.Send
@PostMapping(value = "/choose-payment-type")
public @ResponseBody String createOrder(@RequestBody ChooseOrderPaymentTypeEvent event) {
sagaGateway.send(event);
return event.getId();
}- Handle
@SagaOrchestEventHandler
public void handler(ChooseOrderPaymentTypeEvent event) {
if (paymentId == null) {
CreateReceiptPaymentEvent createReceiptPaymentEvent = new CreateReceiptPaymentEvent();
createReceiptPaymentEvent.setId(UUID.randomUUID().toString());
createReceiptPaymentEvent.setOrderId(orderId);
createReceiptPaymentEvent.setPaymentType(event.getPaymentType());
createReceiptPaymentEvent.setAmount(amount);
sagaGateway.send(createReceiptPaymentEvent);
} else {
TryAgainReceiptPaymentEvent againReceiptPaymentEvent = new TryAgainReceiptPaymentEvent();
againReceiptPaymentEvent.setId(paymentId);
againReceiptPaymentEvent.setPaymentType(event.getPaymentType());
sagaGateway.send(againReceiptPaymentEvent);
}
}Declaration annotation start point method of the Saga class. Maybe declaration more than two.
@SagaOrchestStart
@SagaOrchestEventHandler
public void handler(CreateOrderEvent event){
this.orderId = event.getId();
this.itemsId = event.getItems();
orderService.createOrder(event, amount);
orderPushNotification.sentClientNotification(event.getId(),
"YOUR ORDER CREATED, PLEASE SELECT PAYMENT TYPE AND PAY FROM IT : [ " + PaymentType.getStrings()+" ]");
}Declaration annotation finish/ended point method of the Saga class. Maybe declaration more than two.
@SagaOrchestEnd
@SagaOrchestEventHandler
public void handler(SuccessOrderEvent event) {
orderService.orderSuccessfulPaymentDone(event);
orderPushNotification.sentClientNotification(event.getId(), "ORDER SUCCESSFUL PAYMENT DONE.");
}Declaration annotation any exception to handle of the Saga class. Must is declaration one time in the saga class. Maybe two option @SagaOrchestException declaration method.
- With attribute uz.kassa.microservice.saga.event.SagaExceptionHandler
@SagaOrchestException
public void exceptionHandler(SagaExceptionHandler sagaExceptionHandler){
orderPushNotification.sentClientNotification(sagaExceptionHandler.getSagaId(),
"ORDER EXCEPTION IN EVENT CLASS"+sagaExceptionHandler.getExceptionEventClass()
+" SAGA METHOD NAME "+ sagaExceptionHandler.getExceptionSagaMethodName() +
"EXCEPTION MESSAGE :["+sagaExceptionHandler.getException().getMessage()+"]");
RollbackOrderEvent rollbackOrderEvent = new RollbackOrderEvent();
rollbackOrderEvent.setId(orderId);
sagaGateway.send(rollbackOrderEvent);
}- Without attribute.
@SagaOrchestException
public void exceptionHandler(){
RollbackPaymentEvent rollbackOrderEvent = new RollbackPaymentEvent();
rollbackOrderEvent.setId(paymentId);
sagaGateway.send(rollbackOrderEvent);
}This is bean realization to send events to Saga instance and run it. Actually under the bean hidden big logic. What does SagaGateway do?. It get POJO class and send to Kafka another framework bean listen Kafka and consumer events and redirect to Saga Instance.
sagaGateway.send(againReceiptPaymentEvent);