You will need:
Retrieve the source code:
$ git clone https://github.com/apache/servicecomb-pack.git $ cd servicecomb-pack
Saga can be built in either of the following ways.
Only build the executable files.
$ mvn clean install -DskipTests
build the executable files along with docker image.
$ mvn clean install -DskipTests -Pdocker
build the executable file and saga-distribution
$ mvn clean install -DskipTests -Prelease
After executing either one of the above command, you will find alpha server's executable file in alpha/alpha-server/target/saga/alpha-server-${version}-exec.jar
.
<dependency> <groupId>org.apache.servicecomb.pack</groupId> <artifactId>omega-spring-starter</artifactId> <version>${pack.version}</version> </dependency> <dependency> <groupId>org.apache.servicecomb.pack</groupId> <artifactId>omega-transport-resttemplate</artifactId> <version>${pack.version}</version> </dependency>
Note: Please change the ${pack.version}
to the actual version.
Migration Note:Since 0.3.0 we rename the project repository name from saga to pack. Please update the group id and package name if you migrate your application from saga 0.2.x to pack 0.3.0.
name | 0.2.x | 0.3.x |
---|---|---|
groupId | org.apache.servicecomb.saga | org.apache.servicecomb.pack |
Package Name | org.apache.servicecomb.saga | org.apache.servicecomb.pack |
Add saga annotations and corresponding compensation methods Take a transfer money application as an example:
add @EnableOmega
at application entry to initialize omega configurations and connect to alpha
import org.apache.servicecomb.pack.omega.spring.EnableOmega; import org.springframework.boot.autoconfigure.SpringBootApplication; @SpringBootApplication @EnableOmega public class Application { public static void main(String[] args) { SpringApplication.run(Application.class, args); } }
add @SagaStart
at the starting point of the global transaction
import org.apache.servicecomb.pack.omega.context.annotations.SagaStart; @SagaStart(timeout=10) public boolean transferMoney(String from, String to, int amount) { transferOut(from, amount); transferIn(to, amount); }
Note: By default, timeout is disable.
add @Compensable
at the sub-transaction and specify its corresponding compensation method
import javax.transaction.Transactional; import org.apache.servicecomb.pack.omega.transaction.annotations.Compensable; @Compensable(timeout=5, compensationMethod="cancel") @Transactional public boolean transferOut(String from, int amount) { repo.reduceBalanceByUsername(from, amount); } @Transactional public boolean cancel(String from, int amount) { repo.addBalanceByUsername(from, amount); }
Note The transactions and compensations method should have same arguments. The transactions and compensations implemented by services must be idempotent. We highly recommend to use the Spring @Transactional to guarantee the local transaction.
Note: By default, timeout is disable.
Note: If the starting point of global transaction and local transaction overlaps, both @SagaStart
and @Compensable
are needed.
Repeat step 3 for the transferIn
service.
Since pack-0.3.0, you can access the OmegaContext for the gloableTxId and localTxId in the @Compensable annotated method or the cancel method.
Add TCC annotations and corresponding confirm and cancel methods Take a transfer money application as an example:
add @EnableOmega
at application entry to initialize omega configurations and connect to alpha
import org.apache.servicecomb.pack.omega.spring.EnableOmega; import org.springframework.boot.autoconfigure.SpringBootApplication; @SpringBootApplication @EnableOmega public class Application { public static void main(String[] args) { SpringApplication.run(Application.class, args); } }
add @TccStart
at the starting point of the global transaction
import org.apache.servicecomb.pack.omega.context.annotations.TccStart; @TccStart public boolean transferMoney(String from, String to, int amount) { transferOut(from, amount); transferIn(to, amount); }
Note: By default, timeout is disable.
add @Participate
at the sub-transaction and specify its corresponding compensation method
import javax.transaction.Transactional; import org.apache.servicecomb.pack.omega.transaction.annotations.Participate; @Participate(confirmMethod = "confirm", cancelMethod = "cancel") @Transactional public void transferOut(String from, int amount) { // check banalance } @Transactional public void confirm(String from, int amount) { repo.reduceBalanceByUsername(from, amount); } @Transactional public void cancel(String from, int amount) { repo.addBalanceByUsername(from, amount); }
Note: The confirm and cancel method should have same arguments with participate method, confirm and cancel method implemented by services must be idempotent. We highly recommend to use the Spring @Transactional to guarantee the local transaction.
Note: Current TCC implementation doesn't support timeout.
Note: If the starting point of global transaction and local transaction overlaps, both @TccStart
and @Participate
are needed.
Repeat step 3 for the transferIn
service.
run postgreSQL.
docker run -d -e "POSTGRES_DB=saga" -e "POSTGRES_USER=saga" -e "POSTGRES_PASSWORD=password" -p 5432:5432 postgres
Please check out this document, if you want to use the MySQL instead of postgreSQL.
run alpha. Before running alpha, please make sure postgreSQL is already up. You can run alpha through docker or executable file.
docker run -d -p 8080:8080 -p 8090:8090 -e "JAVA_OPTS=-Dspring.profiles.active=prd -Dspring.datasource.url=jdbc:postgresql://${host_address}:5432/saga?useSSL=false" alpha-server:${saga_version}
java -Dspring.profiles.active=prd -D"spring.datasource.url=jdbc:postgresql://${host_address}:5432/saga?useSSL=false" -jar alpha-server-${saga_version}-exec.jar
Note: Please change ${pack_version}
and ${host_address}
to the actual value before you execute the command.
Note: By default, port 8080 is used to serve omega's request via gRPC while port 8090 is used to query the events stored in alpha.
setup omega. Configure the following values in application.yaml
.
spring: application: name: {application.name} alpha: cluster: address: {alpha.cluster.addresses}
Then you can start your micro-services and access all saga events via http://${alpha-server:port}/events.
See Enabling SSL for details.