Registry, Service Discovery, and Load Balancing on Apache Dubbo

Load Balancing Strategies and Configuration Details

Mon, 01 Jan 0001 00:00:00 +0000

Dubbo has a built-in client-based load balancing mechanism. Below are the currently supported load balancing algorithms. With the automatic service discovery mechanism mentioned earlier, the consumer will automatically use the Weighted Random LoadBalance strategy for service calls.

If you want to adjust the load balancing algorithm, the following are built-in load balancing strategies in the Dubbo framework:

Algorithm	Features	Remarks	Configuration Value
Weighted Random LoadBalance	Weighted Random	Default algorithm, same default weight	random (default)
RoundRobin LoadBalance	Weighted Round Robin	Based on Nginx’s smooth weighted round-robin algorithm, same default weight	roundrobin
LeastActive LoadBalance	Least Active + Weighted Random	Based on the “to each according to their ability” concept	leastactive
Shortest-Response LoadBalance	Shortest Response + Weighted Random	More focused on response speed	shortestresponse
ConsistentHash LoadBalance	Consistent Hash	Deterministic input, deterministic provider, suitable for stateful requests	consistenthash
P2C LoadBalance	Power of Two Choice	Randomly selects two nodes and then chooses the one with fewer connections.	p2c
Adaptive LoadBalance	Adaptive Load Balancing	Based on P2C algorithm, chooses the node with the least load among the two	adaptive

Global Configuration

The default strategy of the Dubbo framework is random weighted random load balancing. To adjust the strategy, simply set the corresponding loadbalance value. For each load balancing strategy value, refer to the table at the top of this document.

How Service Discovery Works: Basic Usage and Configuration Details

Mon, 01 Jan 0001 00:00:00 +0000

Dubbo supports an automatic instance discovery mechanism based on a registry center, where Dubbo providers register instance addresses to the registry center, and Dubbo consumers automatically obtain the latest instance changes by subscribing to changes in the registry center, ensuring that traffic is always forwarded to the correct nodes. Dubbo currently supports various registry centers such as Nacos, Zookeeper, and Kubernetes Service.

Registry Center

The following are some mainstream registry center implementations for Dubbo service discovery. For more extended implementations and working principles, please refer to Registry Center Reference Manual.

Achieving Automatic Service Discovery with Zookeeper as a Registry Center

Mon, 01 Jan 0001 00:00:00 +0000

This example demonstrates the automatic service discovery using Zookeeper as a registry center, based on a Spring Boot application. You can view the full sample code

1 Basic Configuration

1.1 Adding Maven Dependencies

Add dependencies for dubbo, zookeeper, etc. dubbo-spring-boot-starter will automatically add relevant client dependencies for Zookeeper, reducing the cost for users.

For Spring Boot applications, you can use the following dependencies:

<dependency>
 <groupId>org.apache.dubbo</groupId>
 <artifactId>dubbo-spring-boot-starter</artifactId>
 <version>3.3.0</version>
</dependency>
<!-- Use this dependency only when Zookeeper Server version is 3.4.x and below -->
<dependency>
 <groupId>org.apache.dubbo</groupId>
 <artifactId>dubbo-zookeeper-spring-boot-starter</artifactId>
 <version>3.3.0</version>
</dependency>
<!-- Use this dependency only when Zookeeper Server version is 3.5.x and above
<dependency>
 <groupId>org.apache.dubbo</groupId>
 <artifactId>dubbo-zookeeper-curator5-spring-boot-starter</artifactId>
 <version>3.3.0</version>
</dependency>
-->

Here, dubbo-zookeeper-spring-boot-starter or dubbo-zookeeper-curator5-spring-boot-starter manages the zookeeper-related dependencies.

Using Nacos as Registration Center for Automatic Service Discovery

Mon, 01 Jan 0001 00:00:00 +0000

This example demonstrates Nacos as a registration center for automatic service discovery, based on a Spring Boot application. You can view the complete sample code here.

1 Basic Configuration

1.1 Add Dependency

Add the dependencies for dubbo and nacos-client:

<dependencies>
 <dependency>
 <groupId>org.apache.dubbo</groupId>
 <artifactId>dubbo</artifactId>
 <version>3.3.0</version>
 </dependency>
 <dependency>
 <groupId>com.alibaba.nacos</groupId>
 <artifactId>nacos-client</artifactId>
 <version>2.1.0</version>
 </dependency>
</dependencies>

For Spring Boot applications, you can use the following spring-boot-starter:

<dependency>
 <groupId>org.apache.dubbo</groupId>
 <artifactId>dubbo-spring-boot-starter</artifactId>
 <version>3.3.0</version>
</dependency>
<dependency>
 <groupId>org.apache.dubbo</groupId>
 <artifactId>dubbo-nacos-spring-boot-starter</artifactId>
 <version>3.3.0</version>
</dependency>

1.2 Nacos Version

Nacos version mapping:

Service Discovery Based on Kubernetes Service

Mon, 01 Jan 0001 00:00:00 +0000

In the previous two sections, we discussed two registration center patterns: Nacos and Zookeeper, which are more traditional registration center solutions. In a Kubernetes deployment environment, Dubbo supports a service discovery pattern based on Kubernetes Service, which works as shown in the diagram below:

In this mode, service discovery aligns with the user’s deployment and operation tasks. Users define standard Kubernetes Services and Deployments, deploying them to Kubernetes. The Control Plane then monitors the APISERVER resources and interacts with the SDK processes to form a complete service discovery system.