Enterprise Distributed Application Service:Smoothly migrate Dubbo applications to EDAS

Benefits of migration to EDAS

Migration process

1. Required. Migrate applications.

   Applications to be migrated are typically stateless and can be migrated first. This topic focuses on how to migrate applications.

2. Optional. Migrate the Server Load Balancer (SLB) instance or modify the domain name configuration.

   After the application migration is complete, you need to migrate the SLB instance or modify the domain name configuration.

   • SLB
     • If an SLB instance is used before migration, you can reuse the SLB instance after migration.Overview.
     • If no SLB instance is used before migration, we recommend that you create and bind an SLB instance to the entry application, such as API Gateway in the preceding figure, after migration.
   • Domain name
     • The domain name configuration can be retained if the SLB instance can be reused after migration.
     • To create and bind an SLB instance to migrated applications, you must add this SLB instance configuration to the domain name configuration and delete the original SLB instance. For more information, see Change DNS servers for a domain name.
3. Optional:Optional. Migrate storage and message queues.
   • Applications deployed on Alibaba Cloud use Alibaba Cloud services, such as ApsaraDB RDS and Message Queue. Therefore, you do not need to migrate storage and message queues along with applications.
   • If your applications are not deployed on Alibaba Cloud, submit a ticket or contact EDAS technical support to obtain a complete solution for migration to EDAS.

This topic describes how to migrate applications. EDAS provides a demo to show you how to smoothly migrate applications. You can download this demo and run the demo by referring to Readme.

Migration solution

You can use the following two methods to migrate applications without service discontinuity.

Registry switching

Use Dubbo to switch the original service registry to EDAS ConfigServer, develop a new set of applications, and then deploy them to EDAS. Then, use Server Load Balancer (SLB) and configure domain names to switch traffic.

If you use the registry switching method, you can skip the remaining content of this topic. You can use Spring Boot to develop Dubbo microservices applications. For more information, see Use Spring Boot to develop Dubbo microservice-oriented applications.

Dual registration and dual subscription

Access the original service registry and the EDAS service registry when applications are being migrated to enable mutual calling between migrated applications and non-migrated applications.

Dual registration and dual subscription provides the following benefits:

• Migrated applications and non-migrated applications can discover and call each other. This ensures service continuity.
• You need to only add dependencies and modify a line of code to implement dual registration and dual subscription.
• You can view the details of the list of consumer service calls, and view the migration progress in real time.
• You can dynamically modify the policies of service registration and subscription without the need to repeatedly restart applications. You need to restart applications only once in the migration process.

Migrate the first application

We recommend that you start migration from the underlying provider. You can randomly select an application to be migrated if the trace is complex and difficult to analyze. Migrate the selected application by performing the subsequent steps.

1. Add dependencies to the application and modify its configurations. You must modify the configurations when you use the dual registration and dual subscription method.
   Add dependencies to the application and modify its configurations before the application is migrated to EDAS.
   1. Add the edas-dubbo-migration-bom dependency to the pom.xml file.

          <dependency>
                  <groupId>com.alibaba.edas</groupId>
                  <artifactId>edas-dubbo-migration-bom</artifactId>
                  <version>2.6.5.1</version>
                  <type>pom</type>
              </dependency>                                

   2. Add the registry address to application.properties.

      dubbo.registry.address = edas-migration://30.5.XX.XX:9999?service-registry=edas://127.0.0.1:8080,zookeeper://172.31.XX.XX:2181&reference-registry=zookeeper://172.31.XX.XX:2181&config-address=127.0.0.1:8848             

      If your application is not a Spring Boot application, configure the registry addresses in the dubbo.properties file or in the Spring configuration file of the application.

      Parameter	Description
      edas-migration://30.5.XX.XX:9999	The header of the registry address. You do not need to modify the header if the application is registered with multiple service registries. If the log level is WARN or lower, a WARN log may be thrown during startup because Dubbo verifies the IP address and port. The log can be ignored.
      service-registry	The address of the service registry with which the application is registered. By default, the application is registered with multiple service registries. Therefore, multiple registry addresses are written. The registry addresses are in the standard format of Dubbo registry addresses. Use commas (,) to separate multiple registry addresses. Enter the actual ZooKeeper address and port number for the instance that is marked by using the ZooKeeper address 172.31.XX.XX.
      reference-registry	The registry address for service subscription. You can register with multiple service registries or with the original service registry first. The registry addresses are in the standard format of Dubbo registry addresses. Use commas (,) to separate multiple registry addresses.
      config-address	The dynamically pushed address. EDAS converts this address.

   3. For a Spring application that is not developed in Spring Boot, add com.alibaba.edas.dubbo.migration.controller.EdasDubboRegistryRest to the scan path.
2. Verify the result in your on-premises environment.
   Use dynamic configuration for one-time modification.
   1. Complete preparations.
      • Download ZooKeeper
      • Start the lightweight configuration center
   2. Check whether the service is registered.
      • Log on to the lightweight configuration center to view the service in the service provider list.
      • Log on to ZooKeeper to view the information about service registration and consumption.
   3. (Optional) Log on to Nacos to configure the service registration information.
      Note Skip this step if dynamic configuration is not required.

      • DataId: Set this parameter to dubbo.registry.config.
      • Group: Set this parameter to the Dubbo application name that is specified by applicationName, for example, dubbo-migration-demo-server. The application name must be unique because the service registration information is configured at the application level.
      • Configuration Content: The configuration content can be at the application level or the instance IP address level. When multiple network interface controllers (NICs) are used, an error may occur for the instance IP address level.
        • Application level

          dubbo.reference.registry=edas://127.0.0.1:8080   # The service registry with which the service is registered.
          dubbo.service.registry=edas://127.0.0.1:8080,zookeeper:127.0.0.1:2181   # The service registry for service subscription.                                                

        • Instance IP address level

          169.254.XX.XX.dubbo.reference.registry=edas://127.0.0.1:8080,zookeeper:127.0.0.1:2181
          169.254.XX.XX.dubbo.service.registry=edas://127.0.0.1:8080                                                

        When you validate a cluster, you can check whether the configurations at the instance IP address level and those at the application level take effect in sequence.

   4. Check whether the application call is normal and check the registration and subscription relationships of service registries.
      • Spring Boot 1.x: http://ip:port/dubboRegistry
      • Spring Boot 2.x: http://ip:port/actuator/dubboRegistry
3. Deploy the modified application to EDAS.
   You can deploy the application to an Elastic Compute Service (ECS) cluster or a Container Service for Kubernetes (ACK) cluster based on your requirements. You can use the EDAS console or the related tool to deploy the application. For more information, see Overview and Overview.

   • We recommend that you reuse an existing ECS instance by importing the instance to EDAS. This saves costs. For more information, see Create an ECS cluster in the EDAS console.
     Important If you are prompted to perform conversion when you import the ECS instance, back up important data to prevent service impacts caused by data loss.
   • If you do not reuse an existing ECS instance, you must create resources such as an ECS instance and a cluster in the existing virtual private cloud (VPC). This makes the network between applications before and after migration connected so that applications can be migrated. For more information, see Overview.
   • Configure an IP address whitelist for the new ECS instance in products such as a database, a cache, and a message queue. This ensures normal access to the application-dependent third-party components.
4. Verify the result.
   1. Check whether services are normal.
   2. View data about service subscription monitoring.
      If Spring Boot Actuator is enabled for the application, you can access Actuator to view the information about RibbonServerList of each application-subscribed service. You can access Actuator by using the following URLs:

      • Spring Boot 1.x: http://ip:port/dubboRegistry
      • Spring Boot 2.x: http://ip:port/actuator/dubboRegistry
      • dubbo.orig.**: the service registry information that is configured in the application.
      • dubbo.effective.**: the effective service registry information.

Migrate all the other applications

Migrate the other applications to EDAS by referring to Migrate the first application.

Clear the migration configurations

After migration, delete the original service registry configurations and the edas-dubbo-migration-bom dependency that is used during migration.

Modify the registry address by deleting the ZooKeeper configurations. This ensures that consumers subscribe only from EDAS and that providers offer subscriptions only in EDAS. You can modify the registry address by using the following methods:

• Method 1: dynamic configuration

  For more information, see Verify the result in your on-premises environment.

• Method 2: manual modification

  Change the registry address to the address of EDAS Config Server after all the applications are modified.

  dubbo.registry.address = edas-migration://30.5.XX.XX:9999?service-registry=edas://127.0.XX.XX:8080,zookeeper://172.31.XX.XX:2181&reference-registry=edas://127.0.XX.XX:8080&config-address=127.0.0.1:8848                   

  Change the value of reference-registry from zookeeper://172.31.XX.XX:2181 to edas://127.0.XX.XX:8080. Then, deploy applications.

  Note

  Delete zookeeper://172.31.XX.XX:2181 from the service registry configurations if ZooKeeper is no longer required after migration.

  From the long-term perspective, ZooKeeper has no impact on service stability but increases the complexity and the error rate of using service registries in Dubbo. We recommend that you clear the ZooKeeper configurations after migration and restart applications in batches during off-peak hours. The following sample code shows the final registry address.

  dubbo.registry.address = edas://127.0.XX.XX:8080