Dubbo集成Spring Boot

Maven构建

添加什么依赖集成Spring Boot和Dubbo呢？可以看下git地址，pom.xml还是很简单的。
另外还是推荐官方例子:
https://github.com/apache/dubbo-spring-boot-project

Hello World

这个例子中实现简单的Dubbo与Spring Boot集成，并测试消费者暴露的endpoint进行概念验证：

Git地址：https://gitee.com/oneslideicywater/dubbo-playground.git
文档地址： Spring Boot Integration with Dubbo

使用Zookeeper进行服务注册

切到zookeeper分支

特别注意使用：

dubbo.registry.use-as-config-center=false

参考：java.lang.IllegalStateException: zookeeper not connected

生产者和消费者配置基本都是一样的。下面是配置消费者和生产者的两种方式：

application.properties

# Spring boot application，你必须给每个应用添加一个名字
spring.application.name=dubbo-auto-configuration-provider-demo
# Base packages to scan Dubbo Component: @org.apache.dubbo.config.annotation.Service
# 扫描注解了@Service类所在的包
dubbo.scan.base-packages=com.oneslide.helloserviceprovider
# Dubbo Protocol
dubbo.protocol.name=dubbo
## Random port
dubbo.protocol.port=-1
## Dubbo Registry
dubbo.registry.address=zookeeper://192.168.1.3:2181
# 非服务注册中心
dubbo.registry.use-as-config-center=false

YAML方式

spring:
  application:
    name: dubbo-hello-consumer
    
demo:
  service:
    version: 1.0.0
    
dubbo:
  registry:
    address: zookeeper://192.168.1.3:2181
    use-as-config-center: false

测试

Zookeeper

查看Zookeeper的节点：

lide.api.hello.DemoService%26methods%3DsayHello%26pid%3D27708%26release%3D2.7.6%26revision%3D1.0.0%26side%3Dprovider%26timestamp%3D1587192273124%26version%3D1.0.0
[zk: 192.168.1.3:2181(CONNECTED) 33] ls /dubbo
[com.oneslide.api.hello.DemoService]
# 这里是dubbo DemoService服务的树形目录内容
[zk: 192.168.1.3:2181(CONNECTED) 34] ls /dubbo/com.oneslide.api.hello.DemoService
[configurators, consumers, providers, routers]
# 这里是服务消费者对应的Znode，是一个长字符串
[zk: 192.168.1.3:2181(CONNECTED) 35] ls /dubbo/com.oneslide.api.hello.DemoService/consumers
[consumer%3A%2F%2F192.168.59.1%2Fcom.oneslide.api.hello.DemoService%3Fapplication%3Ddubbo-hello-consumer%26category%3Dconsumers%26check%3Dfalse%26dubbo%3D2.0.2%26init%3Dfalse%26interface%3Dcom.oneslide.api.hello.DemoService%26methods%3DsayHello%26pid%3D27072%26qos.enable%3Dfalse%26release%3D2.7.6%26revision%3D1.0.0%26side%3Dconsumer%26sticky%3Dfalse%26timestamp%3D1587192301558%26version%3D1.0.0]
# 这里是服务提供者对应的Znode，是一个长字符串，不过是个空值节点
[zk: 192.168.1.3:2181(CONNECTED) 36] ls /dubbo/com.oneslide.api.hello.DemoService/providers
[dubbo%3A%2F%2F192.168.59.1%3A20880%2Fcom.oneslide.api.hello.DemoService%3Fanyhost%3Dtrue%26application%3Ddubbo-auto-configuration-provider-demo%26deprecated%3Dfalse%26dubbo%3D2.0.2%26dynamic%3Dtrue%26generic%3Dfalse%26interface%3Dcom.oneslide.api.hello.DemoService%26methods%3DsayHello%26pid%3D27708%26release%3D2.7.6%26revision%3D1.0.0%26side%3Dprovider%26timestamp%3D1587192273124%26version%3D1.0.0]
# 这里看到服务消费者对应的Znode是自己的IP地址。
[zk: 192.168.1.3:2181(CONNECTED) 37] get /dubbo/com.oneslide.api.hello.DemoService/consumers/consumer%3A%2F%2F192.168.59.1%2Fcom.oneslide.api.hello.DemoService%3Fapplication%3Ddubbo-hello-consumer%26category%3Dconsumers%26check%3Dfalse%26dubbo%3D2.0.2%26init%3Dfalse%26interface%3Dcom.oneslide.api.hello.DemoService%26methods%3DsayHello%26pid%3D27072%26qos.enable%3Dfalse%26release%3D2.7.6%26revision%3D1.0.0%26side%3Dconsumer%26sticky%3Dfalse%26timestamp%3D1587192301558%26version%3D1.0.0
192.168.59.1

根据上面命令的执行简单分析下，dubbo使用zookeeper作为服务注册中心时，如何实现？

需要明白Zookeeper的两个特性：

1. 临时Znode（ephemeral node）在Zookeeper客户端断连Zookeeper Master自动被删除，从这个角度来讲，服务生产者和消费者都是Zookeeper客户端。
2. watch机制： 客户端可以在节点上添加watch(监视器)，接受节点事件（新增子节点，删除，更改数据等）。

那么知道上面两个背景知识，简单分析一下：

参考：架构

服务提供者在启动时，向注册中心注册自己提供的服务

以上面的例子，/dubbo/com.oneslide.api.hello.DemoService/providers注册一个临时节点：

[zk: 192.168.1.3:2181(CONNECTED) 46] stat /dubbo/com.oneslide.api.hello.DemoService/providers/dubbo%3A%2F%2F192.168.59.1%3A20880%2Fcom.oneslide.api.hello.DemoService%3Fanyhost%3Dtrue%26application%3Ddubbo-auto-configuration-provider-demo%26deprecated%3Dfalse%26dubbo%3D2.0.2%26dynamic%3Dtrue%26generic%3Dfalse%26interface%3Dcom.oneslide.api.hello.DemoService%26methods%3DsayHello%26pid%3D27708%26release%3D2.7.6%26revision%3D1.0.0%26side%3Dprovider%26timestamp%3D1587192273124%26version%3D1.0.0
cZxid = 0x24
ctime = Sat Apr 18 02:44:37 EDT 2020
mZxid = 0x24
mtime = Sat Apr 18 02:44:37 EDT 2020
pZxid = 0x24
cversion = 0
dataVersion = 0
aclVersion = 0
#这里表示这是一个临时节点，值为客户端的SessionID
ephemeralOwner = 0x100002a40e4000b
dataLength = 12
numChildren = 0

但并不是顺序节点，其节点区分有个部分（端口）不一样。

服务消费者在启动时，向注册中心订阅自己所需的服务

在相应的临时节点/dubbo/com.oneslide.api.hello.DemoService/providers添加watch,当有新的服务提供者出现或者有的崩溃，接受事件回调。

怎么查看Zookeeper某个节点注册的watch呢？找了半天没找到！！！

Load-Balance

dubbo支持多种负载均衡，原理不赘述，可以查看Dubbo官网。这里我找了半天文档，总结出四种负载均衡的具体配置方式：

@Service(version = "1.0.0",loadbalance ="roundrobin")

可选值：

• roundrobin
• random (default)
• leastactive 请求处理慢的获得更少的请求（最小活跃连接数）
• consistenthash 一致性hash