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Pack User Guide

ZH doc

Prerequisites

You will need:

  1. JDK 1.8
  2. Maven 3.x
  3. Docker

Build

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.

How to use

Add pack dependencies

    <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

Saga Support

Add saga annotations and corresponding compensation methods Take a transfer money application as an example:

  1. Add @SagaStart at the starting point of the global transaction to prepare the new global transaction context. If you don't specify the SagaStart the flowing sub-transaction will complain that the global transaction id is not found.

    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.

  2. 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.

  3. Add alpha.cluster.address parameters

    alpha:
  cluster:
    address: alpha-server.servicecomb.io:8080

  4. Add omega.spec.names parameters

    omega:
  spec:
    names: saga

  5. Repeat step 2 for the transferIn service.

  6. Since pack-0.3.0, you can access the OmegaContext for the gloableTxId and localTxId in the @Compensable annotated method or the cancel method.

  7. Sinc pack-0.7.0, You can change the distributed transaction specification through the alpha.spec.names parameter, currently supported modes are saga-db (default), tcc-db, saga-akka

Passing transaction context explicitly

In most cases, Omega passing the transaction context for you transparently (see Inter-Service Communication for details). Transaction context passing is implemented in a way of injecting transaction context information on the sender side and extracting it on the receiver side. Below is an example to illustrate this process:

Service A:

@SagaStart
public void foo() {
  restTemplate.postForEntity("http://service-b/bar", ...);
}

Service B:

@GetMapping("/bar")
@Compensable
public void bar() {
  ...
}

Here is how Omega does:

  1. Service A's foo method opens a new global transaction.
  2. TransactionClientHttpRequestInterceptor injects transaction context into request headers when RestTemplate request Service B.
  3. When Service B receive the request, TransactionHandlerInterceptor extract context info from request headers.

Omega supports following implicit transaction context passing:

  1. omega-transport-{dubbo,feign,resttemplate,servicecomb}. Please make sure you add these transport artifacts into your classpath, otherwise you may face an issue that Omega complains about cannot find global transaction id.
  2. Method call in the same thread (based on OmegaContext thread local fields).
  3. java.util.concurrent.Executor{Service} annotated by @OmegaContextAware.

So here comes a problem: what if implicit transaction context passing can't work? For example, Service A invokes Service B via some RPC library and no extension can be made to injecting or extracting transaction context information. In this situation you need explicit transaction context passing. Since ServiceComb Pack 0.5.0, it provides two classes to achieve that.

TransactionContext

Service A:

@SagaStart
public void foo(BarCommand cmd) {
  TransactionContext localTxContext = omegaContext.getTransactionContext();
  someRpc.send(cmd, localTxContext);
}

Service B:

public void listen(BarCommand cmd, TransactionContext injectedTxContext) {
  bar(cmd, injectedTxContext);
}
@Compensable
public void bar(BarCommand cmd, TransactionContext injectedTxContext) {
  ...
  // TransactionContext localTxContext = omegaContext.getTransactionContext();
}

Notice that bar method got an injected transaction context in parameter list, and got a local transaction context from OmegaContext. If service B needs to explictly pass transaction context to another service, local transaction context should be used.

TransactionContextProperties

Service A：

public class BarCommand {}
public class BarCommandWithTxContext 
  extends BarCommand implements TransactionContextProperties {
  // setter getter for globalTxId
  // setter getter for localTxId
}
@SagaStart
public void foo(BarCommand cmd) {
  BarCommandWithTxContext cmdWithTxContext = new BarCommandWithTxContext(cmd);
  cmdWithTxContext.setGlobalTxId(omegaContext.globalTxId());
  cmdWithTxContext.setLocalTxId(omegaContext.localTxId());
  someRpc.send(cmdWithTxContext);
}

Service B:

public void listen(BarCommandWithTxContext cmdWithTxContext) {
  bar(cmdWithTxContext);
}

@Compensable
public void bar(BarCommandWithTxContext cmdWithTxContext) {
  ...
  // TransactionContext localTxContext = omegaContext.getTransactionContext();
}

Similar to the previous approach, cmdWithTxContext.get{Global,Local}TxId() also returns injected transaction context information.

End a Saga manually

Since pack-0.5.0 an attribute name autoClose is added to @SagaStart annotation, this attribute is used to control whether a SagaEndedEvent should be sent to Alpha after SagaStart annotated method is executed (default value is true). When autoClose=false you should use @SagaEnd to send SagaEndedEvent manually, for example:

Service A:

@SagaStart(autoClose=false)
public void foo() {
  restTemplate.postForEntity("http://service-b/bar", ...);
}

Service B:

@GetMapping("/bar")
@Compensable
@SagaEnd
public void bar() {
  ...
}

TCC support

Add TCC annotations and corresponding confirm and cancel methods Take a transfer money application as an example:

  1. 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.

  2. 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.

  3. Add alpha.cluster.address parameters

    alpha:
  cluster:
    address: alpha-server.servicecomb.io:8080

  4. Add omega.spec.names parameters

omega:
  spec:
    names: tcc
  1. Repeat step 2 for the transferIn service.

Passing transaction context explicitly

Just like Saga's @Compensable，@Participate also supports explicit transaction passing. Please refer to Saga - Passing transaction context explicitly for more details.

How to run

  1. 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.

  2. run alpha. Before running alpha, please make sure postgreSQL is already up. You can run alpha through docker or executable file.

    • Run alpha through docker. 
      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}
    • Run alpha through executable file. 
      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.

  3. setup omega. Configure the following values in application.yaml.

    spring:
  application:
    name: {application.name}
alpha:
  cluster:
    address: {alpha.cluster.addresses}
omega:
  spec:
    names: saga

Then you can start your micro-services and access all saga events via http://${alpha-server:port}/saga/events.

Enable SSL for Alpha and Omega

See Enabling SSL for details.

Service discovery support

Alpha instance can register to the discovery service, Omega obtains Alpha's instance list and gRPC address through discovery service

Consul

  1. run alpha

    run with parameter spring.cloud.consul.enabled=true

    java -jar alpha-server-${saga_version}-exec.jar \ 
  --spring.datasource.url=jdbc:postgresql://${host_address}:5432/saga?useSSL=false \
  --spring.datasource.username=saga \
  --spring.datasource.password=saga \
  --spring.cloud.consul.enabled=true \
  --spring.cloud.consul.host=${consul_host} \
  --spring.cloud.consul.port=${consul_port} \
  --spring.profiles.active=prd

    Note: ${consul_host} is consul host, ${consul_port} is consul port

    Note: Check out for more details Spring Cloud Consul 2.x Spring Cloud Consul 1.x

  2. verify registration information

    request curl http://127.0.0.1:8500/v1/agent/services, It responds with the following JSON

    {
    "servicecomb-alpha-server-0-0-0-0-8090": {
        "ID": "servicecomb-alpha-server-0-0-0-0-8090",
        "Service": "servicecomb-alpha-server",
        "Tags": [
            "alpha-server-host=0.0.0.0",
            "alpha-server-port=8080",
            "secure=false"
        ],
        "Meta": {},
        "Port": 8090,
        "Address": "10.50.7.14",
        "Weights": {
            "Passing": 1,
            "Warning": 1
        },
        "EnableTagOverride": false
    }
}

    Note: Tags property is alpha gRPC address

    Note: alpha instance name is servicecomb-alpha-server by default. You can set it by starting parameter  spring.application.name 

  3. setup omega

    edit your pom.xml and add the omega-spring-cloud-consul-starter dependency

    <dependency>
 <groupId>org.apache.servicecomb.pack</groupId>
 <artifactId>omega-spring-cloud-consul-starter</artifactId>
 <version>${pack.version}</version>
</dependency>

    edit your application.yaml , as shown in the following example:

    spring:
  cloud:
    consul:
      discovery:
      	register: false
      host: 127.0.0.1
      port: 8500
      
alpha:
  cluster:
    register:
      type: consul

    • spring.cloud.consul.host property is set to the Consul server’s instance address, spring.cloud.consul.port property is set to the Consul server’s instance port, spring.cloud.consul.discovery.register=false property is not register yourself , check out Spring Boot’s  Spring Cloud Consul 2.x or Spring Cloud Consul 1.x for more details.

    • alpha.cluster.register.type=consul property is omega gets alpha gRPC address from Consul

    • spring boot version compatible

      If your project is not using spring boot 2.3.X, please refer to this list to add a compatible spring-cloud-starter-consul-discovery version

      spring boot spring-cloud-starter-consul-discovery
      2.3.12.RELEASE 2.2.8.RELEASE
      2.1.x.RELEASE 2.1.1.RELEASE
      2.0.x.RELEASE 2.0.2.RELEASE 
        <dependencyManagement>
    <dependencies>
      <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-consul-discovery</artifactId>
        <version>2.2.8.RELEASE</version>
      </dependency>
    </dependencies>
  </dependencyManagement>

    Note: If you define spring.application.name parameter when start alpha, You need to specify this service name in Omega via the parameter alpha.cluster.serviceId

Spring Cloud Eureka

  1. build version of eureka

    build the version support eureka with the -Pspring-cloud-eureka parameter

    git clone https://github.com/apache/servicecomb-pack.git
cd servicecomb-pack
mvn clean install -DskipTests=true -Pspring-cloud-eureka

  2. run alpha

    run with parameter eureka.client.enabled=true

    java -jar alpha-server-${saga_version}-exec.jar \ 
  --spring.datasource.url=jdbc:postgresql://${host_address}:5432/saga?useSSL=false \
  --spring.datasource.username=saga \
  --spring.datasource.password=saga \
  --eureka.client.enabled=true \
  --eureka.client.service-url.defaultZone=http://127.0.0.1:8761/eureka \  
  --spring.profiles.active=prd

    Note: Check out Spring Cloud Netflix 2.x Spring Cloud Netflix 1.x for more details

  3. verify registration information

    request curl http://127.0.0.1:8761/eureka/apps/, It responds with the following XML

    <applications>
  <versions__delta>1</versions__delta>
  <apps__hashcode>UP_1_</apps__hashcode>
  <application>
    <name>SERVICECOMB-ALPHA-SERVER</name>
    <instance>
      <instanceId>0.0.0.0::servicecomb-alpha-server:8090</instanceId>
      <hostName>0.0.0.0</hostName>
      <app>SERVICECOMB-ALPHA-SERVER</app>
      <ipAddr>0.0.0.0</ipAddr>
      <status>UP</status>
   ...
      <metadata>
        <management.port>8090</management.port>
        <servicecomb-alpha-server>0.0.0.0:8080</servicecomb-alpha-server>
      </metadata>
      ...
    </instance>
  </application>
</applications>

    Note: <servicecomb-alpha-server> property is alpha gRPC address

    Note: alpha instance name is SERVICECOMB-ALPHA-SERVER by default. You can set it by starting parameter  spring.application.name 

  4. setup omega

    edit your pom.xml and add the omega-spring-cloud-eureka-starter dependency

    <dependency>
 <groupId>org.apache.servicecomb.pack</groupId>
 <artifactId>omega-spring-cloud-eureka-starter</artifactId>
 <version>${pack.version}</version>
</dependency>

    edit your application.yaml , as shown in the following example:

    eureka:
  client:
    service-url:
      defaultZone: http://127.0.0.1:8761/eureka
alpha:
  cluster:
    register:
      type: eureka

    • eureka.client.service-url.defaultZone property is set to the Eureka server’s instance address, check out Spring Boot’s  Spring Cloud Netflix 2.x or Spring Cloud Netflix 1.x for more details.

    • alpha.cluster.register.type=eureka property is omega gets alpha gRPC address from Eureka

    • spring boot version compatible

      If your project is not using spring boot 2.3.X, please refer to this list to add a compatible spring-cloud-starter-netflix-eureka-client version

      spring boot spring-cloud-starter-netflix-eureka-client
      2.3.12.RELEASE 2.2.10.RELEASE
      2.1.x.RELEASE 2.1.1.RELEASE
      2.0.x.RELEASE 2.0.3.RELEASE 
        <dependencyManagement>
    <dependencies>
      <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        <version>2.2.10.RELEASE</version>
      </dependency>
    </dependencies>
  </dependencyManagement>

    Note: If you define spring.application.name parameter when start alpha, You need to specify this service name in Omega via the parameter alpha.cluster.serviceId

Spring Cloud Zookeeper

  1. run alpha

    run with parameter spring.cloud.zookeeper.enabled=true

    java -jar alpha-server-${saga_version}-exec.jar \ 
  --spring.datasource.url=jdbc:postgresql://${host_address}:5432/saga?useSSL=false \
  --spring.datasource.username=saga \
  --spring.datasource.password=saga \
  --spring.cloud.zookeeper.enabled=true \
  --spring.cloud.zookeeper.connectString=${zookeeper_host}:${zookeeper_port} \
  --spring.profiles.active=prd

    Note: ${zookeeper_host} is zookeeper host, ${zookeeper_port} is zookeeper port

    Note: Check out for more details Spring Cloud Zookeeper 2.x Spring Cloud Zookeeper 1.x

  2. verify registration information

    view znode /services/servicecomb-alapha-server

     {
     "name": "servicecomb-alpha-server",
     "id": "9b2223ae-50e6-49a6-9f3b-87a1ff06a016",
     "address": "arch-office",
     "port": 8090,
     "sslPort": null,
     "payload": {
         "@class": "org.springframework.cloud.zookeeper.discovery.ZookeeperInstance",
         "id": "servicecomb-alpha-server-1",
         "name": "servicecomb-alpha-server",
         "metadata": {
         "servicecomb-alpha-server": "arch-office:8080"
         }
     },
     "registrationTimeUTC": 1558000134185,
     "serviceType": "DYNAMIC",
     "uriSpec": {
         "parts": [
         {
             "value": "scheme",
             "variable": true
         },
         {
             "value": "://",
             "variable": false
         },
         {
             "value": "address",
             "variable": true
         },
         {
             "value": ":",
             "variable": false
         },
         {
             "value": "port",
             "variable": true
         }
         ]
     }
 }

    Note: metadata property is alpha gRPC address

    Note: alpha instance name is servicecomb-alpha-server by default. You can set it by starting parameter  spring.application.name 

  3. setup omega

    edit your pom.xml and add the omega-spring-cloud-zookeeper-starter dependency

    <dependency>
 <groupId>org.apache.servicecomb.pack</groupId>
 <artifactId>omega-spring-cloud-zookeeper-starter</artifactId>
 <version>${pack.version}</version>
</dependency>

    edit your application.yaml , as shown in the following example:

    spring:
  cloud:
    zookeeper:
      enabled: true
      connectString: 127.0.0.1:2181
      
alpha:
  cluster:
    register:
      type: zookeeper

    • spring.cloud.zookeeper.connectString property is set to the Zookeeper server’s instance address, check out Spring Boot’s  Spring Cloud Zookeeper 2.x Spring Cloud Zookeeper 1.x for more details.

    • alpha.cluster.register.type=zookeeper property is omega gets alpha gRPC address from Zookeeper

    • spring boot version compatible

      If your project is not using spring boot 2.3.X, please refer to this list to add a compatible spring-cloud-starter-zookeeper-discovery version

      spring boot spring-cloud-starter-zookeeper-discovery
      2.3.12.RELEASE 2.2.5.RELEASE
      2.1.x.RELEASE 2.1.1.RELEASE
      1.5.17.RELEASE 1.2.2.RELEASE 
        <dependencyManagement>
    <dependencies>
      <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-zookeeper-discovery</artifactId>
        <version>2.2.5.RELEASE</version>
      </dependency>
    </dependencies>
  </dependencyManagement>

    Note: If you define spring.application.name parameter when start alpha, You need to specify this service name in Omega via the parameter alpha.cluster.serviceId

Spring Cloud Nacos Discovery

  1. run alpha

    run with parameter nacos.client.enabled=true

    java -jar alpha-server-${saga_version}-exec.jar \ 
  --spring.datasource.url=jdbc:postgresql://${host_address}:5432/saga?useSSL=false \
  --spring.datasource.username=saga \
  --spring.datasource.password=saga \
  --spring.cloud.nacos.discovery.enabled=true \
  --spring.cloud.nacos.discovery.serverAddr=${nacos_host}:${nacos_port} \
  --nacos.client.enabled=true \
  --spring.profiles.active=prd

    Note: ${nacos_host} is nacos host, ${nacos_port} is nacos port

    Note: Check out for more details Spring Cloud Nacos Discovery

  2. verify registration information

    request curl -X GET 'http://127.0.0.1:8848/nacos/v1/ns/instance/list?serviceName=servicecomb-alpha-server‘ , It responds with the following JSON

     {
     "metadata": {},
     "dom": "servicecomb-alpha-server",
     "cacheMillis": 3000,
     "useSpecifiedURL": false,
     "hosts": [
         {
         "valid": true,
         "marked": false,
         "metadata": {
             "preserved.register.source": "SPRING_CLOUD",
             "servicecomb-alpha-server": "192.168.2.28:8080"
         },
         "instanceId": "192.168.2.28#8090#DEFAULT#DEFAULT_GROUP@@servicecomb-alpha-server",
         "port": 8090,
         "healthy": true,
         "ip": "192.168.2.28",
         "clusterName": "DEFAULT",
         "weight": 1,
         "ephemeral": true,
         "serviceName": "servicecomb-alpha-server",
         "enabled": true
         }
     ],
     "name": "DEFAULT_GROUP@@servicecomb-alpha-server",
     "checksum": "d9e8deefd1c4f198980f4443d7c1b1fd",
     "lastRefTime": 1562567653565,
     "env": "",
     "clusters": ""
     }

    Note: metadata property is alpha gRPC address

    Note: alpha instance name is servicecomb-alpha-server by default. You can set it by starting parameter  spring.application.name 

  3. setup omega

    edit your pom.xml and add the omega-spring-cloud-nacos-starter dependency

    <dependency>
 <groupId>org.apache.servicecomb.pack</groupId>
 <artifactId>omega-spring-cloud-nacos-starter</artifactId>
 <version>${pack.version}</version>
</dependency>

    edit your application.yaml , as shown in the following example:

    spring:
  cloud:
    nacos:
      discovery:
         enabled: true
         serverAddr: 127.0.0.1:8848
      
alpha:
  cluster:
    register:
      type: nacos

    • spring.cloud.nacos.discovery.serverAddr property is set to the Nacos server’s instance address, check out Spring Boot’s  Spring Cloud Nacos Discovery for more details.

    • alpha.cluster.register.type=nacos property is omega gets alpha gRPC address from Nacos

    • spring boot version compatible

      If your project is not using spring boot 2.3.X, please refer to this list to add a compatible spring-cloud-starter-alibaba-nacos-discovery version

      | spring boot | spring-cloud-starter-alibaba-nacos-discovery | ----------------| ------------- | ------------------------------------- | | 2.3.12.RELEASE | 2.2.6.RELEASE | | 2.1.x.RELEASE | 0.2.2.RELEASE | | 1.5.17.RELEASE | 0.1.2.RELEASE |

        <dependencyManagement>
    <dependencies>
      <dependency>
        <groupId>com.alibaba.cloud</groupId>
        <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
        <version>2.2.6.RELEASE</version>
      </dependency>
    </dependencies>
  </dependencyManagement>

    Note: If you define spring.application.name parameter when start alpha, You need to specify this service name in Omega via the parameter alpha.cluster.serviceId

Cluster

Alpha can be highly available by deploying multiple instances, enable cluster support with the alpha.cluster.master.enabled=true parameter.

Native transports

Alpha enabled JNI transports support with alpha.feature.nativetransport=true, These JNI transports add features specific to a particular platform, generate less garbage, and generally improve performance when compared to the NIO based transport.

Pack Distributed Transaction Specifications

Saga-Akka Specifications

Upgrade Guide

Pack 0.6.0 Migration Guide