Empty-push protection

Limits

Nacos Java Client 1.4.1 and later support client-side empty-push protection.

Procedure

• If you use the Nacos-Client for Java:

  1. Import the nacos-client dependency:

     <!-- ${nacos-client.version} must be 1.4.1 or later -->
     <dependency>
         <groupId>com.alibaba.nacos</groupId>
         <artifactId>nacos-client</artifactId>
         <version>${nacos-client.version}</version>
     </dependency>

  2. Configure the settings in your program code as follows:

     Properties properties = new Properties();
     properties.put(PropertyKeyConst.SERVER_ADDR, "${mseNacosInstanceDomainName}");
     properties.put(PropertyKeyConst.NAMING_PUSH_EMPTY_PROTECTION, "true");
     NamingService naming = NamingFactory.createNamingService(properties);

• If you use the Spring Cloud Alibaba framework, add the following configuration to the application configuration file.

  spring.cloud.nacos.discovery.namingPushEmptyProtection=true

• If you use the Dubbo framework, add the following configuration to the registry link URL in the Dubbo configuration file.

  dubbo.registry.address=nacos://${mseNacosInstanceDomainName}:8848?namingPushEmptyProtection=true

Limits

The Nacos database engine version must be 2.1.0.0 or later. For more information, see Upgrade the Nacos database engine version.

Procedure

The method to enable empty-push protection varies based on the Nacos database engine version.

• If your MSE Nacos database engine version is 2.1.0.0 or 2.1.0.1, empty-push protection is enabled automatically. No action is required.

• If your MSE Nacos database engine version is 2.1.0.2 or later, perform the following steps to enable empty-push protection.

  1. Log on to the MSE console, and select a region in the top navigation bar.

  2. In the left-side navigation pane, choose Microservices Registry > Instances.

  3. On the Instances page, click the name of the instance.

  4. In the navigation pane on the left, click Parameter Settings. On the Parameter Settings page, in the Real-time Effective Parameters section, click Edit in the Actions column for forcePushEmptyProtectionForAllService.

  5. In the Edit Parameters dialog box, set Value to Yes and click OK.

     Note

     To ensure maximum business availability, we recommend that you enable empty-push protection by setting the Value of forcePushEmptyProtectionForAllService to Yes.

Verify the results

When a service triggers empty-push protection, you can see the message Trigger push empty protection for Service in the ${user.home}/logs/nacos/naming.log file on the consumer's node.

Normally, this message does not appear frequently. If it does, you can troubleshoot based on the following scenarios.

• Subscribing to a non-existent service.

  If an application subscribes to a non-existent service, check whether the application still needs this dependency. If not, delete the invalid dependency. If the dependency is still needed, republish the service provider.

• The service provider to which the application subscribed is empty.

  • Check whether the service provider frequently goes offline.

  • Check whether the network connectivity between the service provider and the MSE Nacos cluster is unstable. An unstable connection can cause Nacos to consider the provider offline.

Locate the service that triggers empty-push protection

The error message contains the service that triggered the protection. You can identify which empty service the consumer has subscribed to from Service{namespace='XXX', group='xx', name='xxxxxxx', ephemeral=true, revision=0}.

Common scenarios that trigger empty-push protection

Scenarios where empty-push protection is enforced

In MSE Nacos 2.1.0.2 and later, the optimized empty-push protection logic protects all empty service lists only when forcePushEmptyProtectionForAllService is enabled. However, in the following scenarios, the system automatically enables empty-push protection to ensure availability and stability, even if the forcePushEmptyProtectionForAllService switch is off.

• When an engine node is being upgraded, restarted, or undergoing automatic fault recovery, the node automatically enables empty-push protection for all services for 2 minutes to ensure business availability during this period.

• When all instances of a service are removed, the cluster automatically enables empty-push protection for that service for 1 minute. This prevents empty pushes caused by issues such as network jitter or short-term service provider failures, which ensures business availability.