Dubbo is a high-performance and excellent service framework open sourced by Alibaba, which enables applications to realize the output and input functions of services through high-performance RPC, and can be seamlessly integrated with the Spring framework. Here is a set of video tutorials about dubbo to share with you, including introduction to dubbo, advanced dubbo&dubbox, and actual combat of dubbo distributed projects.

Main core components

Remoting: A network communication framework that implements sync-over-async and request-response message mechanisms.

RPC: An abstraction for remote procedure calls that supports load balancing, disaster recovery and clustering functions

Registry: Service catalog framework for service registration and service event publishing and subscription

working principle

Provider

The exposed service party is called a "service provider".

Consumer

The party calling a remote service is called a "service consumer".

Registry

The central directory service for service registration and discovery is called the "Service Registry".

Monitor

The log service that counts the invocation times and invocation time of the service is called "Service Monitoring Center".

(1) Connectivity:

The registration center is responsible for the registration and search of service addresses, which is equivalent to a directory service. Service providers and consumers only interact with the registration center at startup. The registration center does not forward requests, so the pressure is small.

The monitoring center is responsible for counting the number of calls and calling time of each service. The statistics are first aggregated in memory and then sent to the monitoring center server every minute, and displayed in a report.

The service provider registers the services it provides with the registration center, and reports the calling time to the monitoring center, which does not include network overhead

The service consumer obtains the address list of service providers from the registration center, directly calls the provider according to the load algorithm, and reports the calling time to the monitoring center, which includes network overhead.

The registration center, service provider, and service consumer are all long-term connections, except for the monitoring center

The registration center perceives the existence of the service provider through the long connection. If the service provider is down, the registration center will immediately push the event to notify the consumer

The registration center and monitoring center are all down, which does not affect the running providers and consumers. The consumer caches the provider list locally.

The registration center and monitoring center are optional, and service consumers can directly connect to service providers

(2) Robustness:

The downtime of the monitoring center does not affect the use, but only part of the sampled data is lost

数据库宕掉后，注册中心仍能通过缓存提供服务列表查询，但不能注册新服务

注册中心对等集群，任意一台宕掉后，将自动切换到另一台

注册中心全部宕掉后，服务提供者和服务消费者仍能通过本地缓存通讯

服务提供者无状态，任意一台宕掉后，不影响使用

服务提供者全部宕掉后，服务消费者应用将无法使用，并无限次重连等待服务提供者恢复

(3) 伸缩性：

注册中心为对等集群，可动态增加机器部署实例，所有客户端将自动发现新的注册中心

服务提供者无状态，可动态增加机器部署实例，注册中心将推送新的服务提供者信息给消费者