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Posted to notifications@dubbo.apache.org by GitBox <gi...@apache.org> on 2021/07/20 05:47:24 UTC
[GitHub] [dubbo] zhangyz-hd commented on issue #8010: Write/Delete configurators cause unnecessary reregister and netty connections
zhangyz-hd commented on issue #8010:
URL: https://github.com/apache/dubbo/issues/8010#issuecomment-883083120
# 进一步分析
## 场景：
- zookeeper注册中心，按接口服务发现模式
- 注册中心1个提供者，1个override://weight=200
## 过程：
### 1，消费者启动
收到如下notify
1. **空的routers，正常**：
```
empty://192.168.3.198/org.apache.dubbo.demo.DemoService?application=dubbo-demo-annotation-consumer&category=routers&dubbo=2.0.2&init=false&interface=org.apache.dubbo.demo.DemoService&metadata-type=remote&methods=sayHello&pid=4366&qos.enable=false&side=consumer&sticky=false×tamp=1626748727511
```
2. **一条override，正常**：
```
override://0.0.0.0/org.apache.dubbo.demo.DemoService?category=configurators&dynamic=false&weight=200
```
3. 附带weight=200权重的**提供者url**，姑且算正常（因为注册中心写入override后，提供者会reExport）：
```
dubbo://192.168.3.198:20881/org.apache.dubbo.demo.DemoService?anyhost=true&application=dubbo-demo-annotation-provider&deprecated=false&dubbo=2.0.2&dynamic=true&generic=false&interface=org.apache.dubbo.demo.DemoService&metadata-type=remote&methods=sayHello&pid=3865&release=release&service.name=ServiceBean:/org.apache.dubbo.demo.DemoService&side=provider×tamp=1626744024684&weight=200
```
4. 连接服务提供方
```
[20/07/21 11:17:13:195 CST] NettyClientWorker-1-1 INFO netty4.NettyClientHandler: [DUBBO] The connection of /192.168.3.198:56588 -> /192.168.3.198:20881 is established., dubbo version: , current host: 192.168.3.198
[20/07/21 11:17:13:202 CST] main INFO transport.AbstractClient: [DUBBO] Successed connect to server /192.168.3.198:20881 from NettyClient 192.168.3.198 using dubbo version , channel is NettyChannel [channel=[id: 0x5678db4a, L:/192.168.3.198:56588 - R:/192.168.3.198:20881]], dubbo version: , current host: 192.168.3.198
[20/07/21 11:17:13:203 CST] main INFO transport.AbstractClient: [DUBBO] Start NettyClient /192.168.3.198 connect to the server /192.168.3.198:20881, dubbo version: , current host: 192.168.3.198
```
ReferenceCountExchangeClient计数器=1
### 2，服务调用
正常
### 3，删除注册中心的override
1. 消费者收到因为监听configurators而收到空的configurator，this.configurators清空：
```
empty://192.168.3.198/org.apache.dubbo.demo.DemoService?application=dubbo-demo-annotation-consumer&category=configurators&dubbo=2.0.2&init=false&interface=org.apache.dubbo.demo.DemoService&metadata-type=remote&methods=sayHello&pid=4366&qos.enable=false&side=consumer&sticky=false×tamp=1626748727511
```
因为cachedInvokerUrls中附带着weight=200，因此下一步oldUrlInvokerMap和newUrlInvokerMap相同，没有invoker被destroy。
2. 提供者reExport，消费者收到空提供购买者列表，
```
empty://192.168.3.198/org.apache.dubbo.demo.DemoService?application=dubbo-demo-annotation-consumer&category=providers&dubbo=2.0.2&init=false&interface=org.apache.dubbo.demo.DemoService&metadata-type=remote&methods=sayHello&pid=4366&qos.enable=false&side=consumer&sticky=false×tamp=1626748727511
```
ReferenceCountExchangeClient计数器减到0，变成LazyConnectExchangeClient
3. 提供者完成Export，消费者收到新的提供者列表，
```
dubbo://192.168.3.198:20881/org.apache.dubbo.demo.DemoService?anyhost=true&application=dubbo-demo-annotation-consumer&check=false&deprecated=false&dubbo=2.0.2&dynamic=true&generic=false&init=false&interface=org.apache.dubbo.demo.DemoService&metadata-type=remote&methods=sayHello&pid=4366&qos.enable=false®ister.ip=192.168.3.198&release=release&remote.application=dubbo-demo-annotation-provider&service.name=ServiceBean:/org.apache.dubbo.demo.DemoService&side=consumer&sticky=false×tamp=1626744024684
```
ReferenceCountExchangeClient计数器+1。之后的服务调用，LazyConnectExchangeClient去和提供者建立连接
```
[20/07/21 11:17:43:789 CST] main INFO dubbo.LazyConnectExchangeClient: [DUBBO] Lazy connect to dubbo://192.168.3.198:20881/org.apache.dubbo.demo.DemoService?anyhost=true&application=dubbo-demo-annotation-consumer&check=false&codec=dubbo&connect.lazy.initial.state=true&deprecated=false&dubbo=2.0.2&dynamic=true&generic=false&heartbeat=60000&init=false&interface=org.apache.dubbo.demo.DemoService&metadata-type=remote&methods=sayHello&pid=4812&qos.enable=false®ister.ip=192.168.3.198&release=release&remote.application=dubbo-demo-annotation-provider&send.reconnect=true&service.name=ServiceBean:/org.apache.dubbo.demo.DemoService&side=consumer&sticky=false×tamp=1626744024684&weight=200, dubbo version: , current host: 192.168.3.198
[20/07/21 11:17:43:792 CST] main INFO transport.AbstractClient: [DUBBO] Successed connect to server /192.168.3.198:20881 from NettyClient 192.168.3.198 using dubbo version , channel is NettyChannel [channel=[id: 0x0d0a3f3a, L:/192.168.3.198:56601 - R:/192.168.3.198:20881]], dubbo version: , current host: 192.168.3.198
[20/07/21 11:17:43:792 CST] NettyClientWorker-1-2 INFO netty4.NettyClientHandler: [DUBBO] The connection of /192.168.3.198:56601 -> /192.168.3.198:20881 is established., dubbo version: , current host: 192.168.3.198
[20/07/21 11:17:43:792 CST] main INFO transport.AbstractClient: [DUBBO] Start NettyClient /192.168.3.198 connect to the server /192.168.3.198:20881, dubbo version: , current host: 192.168.3.198
```
此时，消费者就存在2个和提供者之间的连接
```
The connection of /192.168.3.198:56588 -> /192.168.3.198:20881The connection of /192.168.3.198:56601 -> /192.168.3.198:20881
```
### 4，重复写入override，删除override步骤
后续每次写入override，删除override，提供者和消费者之间就多一个连接，过程基本同3，都是因为每次产生了额外的LazyConnectExchangeClient
## 补充：
1. 将提供者reExport行为去除，不会出现上述现象，因为消费者端ReferenceCountExchangeClient计数器不会归0；
2. 将提供者reExport行为中先处理reExportRegister，再处理reExportUnregister，也不会出现上述现象，因为消费者端ReferenceCountExchangeClient计数器是先加再减，也不会归0。
## 怀疑：
当ReferenceCountExchangeClient计数器变成0，转为LazyConnectExchangeClient后，如果这个连接还需要被继续使用，着出现连接无法回收的情况。
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