What are the core architecture and features of the Dubbo framework? How does Dubbo implement service governance?

Dubbo is a high-performance Java RPC framework open-sourced by Alibaba, widely used in microservice architectures:

Core Architecture:

1. Service Provider

• Application that exposes services
• Registers services with the registry at startup
• Can deploy multiple instances for load balancing

2. Service Consumer

• Application that calls remote services
• Subscribes to services from the registry at startup
• Calls remote services through proxies

3. Registry

• Core component for service registration and discovery
• Common implementations: Zookeeper, Nacos, Redis
• Responsible for maintaining service lists and health status

4. Monitor

• Statistics on service call counts and call times
• Provides data support for service governance
• Common implementations: Dubbo Admin, Prometheus

5. Container

• Service runtime container
• Common: Spring Container, Spring Boot

Core Features:

1. Remote Call

• Supports multiple protocols: Dubbo, RMI, Hessian, HTTP, Webservice, Thrift, REST
• Default uses Dubbo protocol (based on Netty)
• Supports both synchronous and asynchronous calls

2. Cluster Fault Tolerance

• Failover: Automatic failover, default strategy
• Failfast: Fast failure, only initiates one call
• Failsafe: Fail-safe, ignores exceptions
• Failback: Automatic recovery, records failed requests in background
• Forking: Parallel calls, returns as soon as one succeeds
• Broadcast: Broadcast call, all calls must succeed

3. Load Balancing

• Random: Random, sets random probability based on weights
• RoundRobin: Round robin, sets round robin ratio based on reduced weights
• LeastActive: Least active call count
• ConsistentHash: Consistent hash, requests with same parameters always go to same provider

4. Service Degradation

• Mock data
• Return null
• Throw specified exception

5. Service Rate Limiting

• Concurrency limit
• QPS limit

6. Service Routing

• Conditional routing
• Tag routing
• Script routing

7. Configuration Center

• Dynamic configuration
• Configuration version management
• Configuration push

Usage Example:

Service Provider:

java
@Service
public class UserServiceImpl implements UserService {
    @Override
    public User getUserById(Long id) {
        return new User(id, "Zhang San");
    }
}

// Configuration
<dubbo:service interface="com.example.UserService" ref="userService"/>

Service Consumer:

java
// Configuration
<dubbo:reference interface="com.example.UserService" id="userService"/>

// Usage
@Autowired
private UserService userService;

public void test() {
    User user = userService.getUserById(1L);
}

Advantages:

• High Performance: Based on Netty, supports long connections
• Ease of Use: Deep integration with Spring
• Extensibility: Supports multiple protocols and load balancing strategies
• Service Governance: Comprehensive service governance features
• Active Community: Continuously maintained by Alibaba and community

Applicable Scenarios:

• Java microservice architecture
• Internal service calls
• High concurrency scenarios
• Systems requiring comprehensive service governance