路由状态采集

功能说明

路由状态收集功能可用于识别可能影响服务性能的任何潜在问题，识别可能阻碍服务尽可能高效使用的任何潜在瓶颈或问题，确保服务平稳运行，用户在尝试访问服务时不会遇到任何问题，允许用户检查路由的状态是启用还是禁用，确保仅使用授权的服务，并且访问仅限于具有适当授权的人员。

使用场景

Dubbo 的很多流量治理能力是基于 Router 进行实现的，在生产环境中，如果出现流量结果不符合预期的情况，可以通过路由状态命令来查看路由的状态，以此来定位可能存在的问题。

使用方式

查看路由缓存状态

Dubbo 在收到地址变更的时候，会将地址信息推送给所有的 Router，这些 Router 可以在此阶段提前计算路由的分组，缓存起来，以避免在调用时需要遍历所有的提供者计算分组参数。在 Dubbo 3 中引入的 StateRouter 提供了通过 qos 命令工具实时获取每个路由的状态的能力。

运维人员可以通过 getRouterSnapshot 命令获取路由的状态。具体命令使用方式可以参考 getRouterSnapshot 命令文档。

注：此功能仅支持 StateRoute，且 StateRouter 需要基于 AbstractStateRouter 实现 doBuildSnapshot 接口。

查看实际请求的路由计算结果

Dubbo 3 中默认在路由筛选后为空的时候打印路由计算的节点状态。运维人员可以通过日志判断每个路由的计算结果是否符合预期。

日志格式

No provider available after route for the service 服务 from registry 注册中心地址 on the consumer 消费端IP using the dubbo version 3.0.7. Router snapshot is below: 
[ Parent (Input: 当前节点输入地址数) (Current Node Output: 当前节点计算结果数) (Chain Node Output: 当前节点和后级节点交集结果数) ] Input: 输入的地址示例（显示最多 5 个） -> Chain Node Output: 当前节点输出的地址示例（显示最多 5 个）
  [ 路由名称 (Input: 当前节点输入地址数) (Current Node Output: 当前节点计算结果数) (Chain Node Output: 当前节点和后级节点交集结果数) Router message: 路由日志 ] Current Node Output: 当前节点输出的地址示例（显示最多 5 个）
    [ 路由名称 (Input: 当前节点输入地址数) (Current Node Output: 当前节点计算结果数) (Chain Node Output: 当前节点和后级节点交集结果数) Router message: 路由日志 ] Current Node Output: 当前输入的地址示例（显示最多 5 个）

注意：

路由日志需要依赖路由实现判断 needToPrintMessage 参数，并在需要时写入 messageHolder 路由日志
由于多级路由结果是结果取交集的，所以当前节点计算结果数可能和后级取交后为空

日志示例

[19/07/22 07:42:46:046 CST] main  WARN cluster.RouterChain:  [DUBBO] No provider available after route for the service org.apache.dubbo.samples.governance.api.DemoService from registry 30.227.64.173 on the consumer 30.227.64.173 using the dubbo version 3.0.7. Router snapshot is below: 
[ Parent (Input: 2) (Current Node Output: 2) (Chain Node Output: 0) ] Input: 30.227.64.173:20881,30.227.64.173:20880 -> Chain Node Output: Empty
  [ MockInvokersSelector (Input: 2) (Current Node Output: 2) (Chain Node Output: 0) Router message: invocation.need.mock not set. Return normal Invokers. ] Current Node Output: 30.227.64.173:20881,30.227.64.173:20880
    [ StandardMeshRuleRouter (Input: 2) (Current Node Output: 2) (Chain Node Output: 0) Router message: MeshRuleCache has not been built. Skip route. ] Current Node Output: 30.227.64.173:20881,30.227.64.173:20880
      [ TagStateRouter (Input: 2) (Current Node Output: 0) (Chain Node Output: 0) Router message: FAILOVER: return all Providers without any tags ] Current Node Output: Empty, dubbo version: 3.0.7, current host: 30.227.64.173

开启路由全采样

在一些特殊情况下，请求可能调用到错误的服务端，但是因为选址非空，所以无法看到路由的过程信息，此时可以通过 qos 开启路由全采样。通过 qos 的 getRecentRouterSnapshot 命令可以远程获取最近的路由快照。

dubbo>getRecentRouterSnapshot
1658224330156 - Router snapshot service com.dubbo.dubbointegration.BackendService from registry 172.18.111.184 on the consumer 172.18.111.184 using the dubbo version 3.0.9 is below: 
[ Parent (Input: 2) (Current Node Output: 2) (Chain Node Output: 2) ] Input: 172.18.111.187:20880,172.18.111.183:20880 -> Chain Node Output: 172.18.111.187:20880,172.18.111.183:20880
  [ MockInvokersSelector (Input: 2) (Current Node Output: 2) (Chain Node Output: 2) Router message: invocation.need.mock not set. Return normal Invokers. ] Current Node Output: 172.18.111.187:20880,172.18.111.183:20880
    [ StandardMeshRuleRouter (Input: 2) (Current Node Output: 2) (Chain Node Output: 2) Router message: MeshRuleCache has not been built. Skip route. ] Current Node Output: 172.18.111.187:20880,172.18.111.183:20880
      [ TagStateRouter (Input: 2) (Current Node Output: 2) (Chain Node Output: 2) Router message: Disable Tag Router. Reason: tagRouterRule is invalid or disabled ] Current Node Output: 172.18.111.187:20880,172.18.111.183:20880
        [ ServiceStateRouter (Input: 2) (Current Node Output: 2) (Chain Node Output: 2) Router message: Directly return. Reason: Invokers from previous router is empty or conditionRouters is empty. ] Current Node Output: 172.18.111.187:20880,172.18.111.183:20880
          [ AppStateRouter (Input: 2) (Current Node Output: 2) (Chain Node Output: 2) Router message: Directly return. Reason: Invokers from previous router is empty or conditionRouters is empty. ] Current Node Output: 172.18.111.187:20880,172.18.111.183:20880

1658224330156 - Router snapshot service com.dubbo.dubbointegration.BackendService from registry 172.18.111.184 on the consumer 172.18.111.184 using the dubbo version 3.0.9 is below: 
[ Parent (Input: 2) (Current Node Output: 2) (Chain Node Output: 2) ] Input: 172.18.111.187:20880,172.18.111.183:20880 -> Chain Node Output: 172.18.111.187:20880,172.18.111.183:20880
  [ MockInvokersSelector (Input: 2) (Current Node Output: 2) (Chain Node Output: 2) Router message: invocation.need.mock not set. Return normal Invokers. ] Current Node Output: 172.18.111.187:20880,172.18.111.183:20880
    [ StandardMeshRuleRouter (Input: 2) (Current Node Output: 2) (Chain Node Output: 2) Router message: MeshRuleCache has not been built. Skip route. ] Current Node Output: 172.18.111.187:20880,172.18.111.183:20880
      [ TagStateRouter (Input: 2) (Current Node Output: 2) (Chain Node Output: 2) Router message: Disable Tag Router. Reason: tagRouterRule is invalid or disabled ] Current Node Output: 172.18.111.187:20880,172.18.111.183:20880
        [ ServiceStateRouter (Input: 2) (Current Node Output: 2) (Chain Node Output: 2) Router message: Directly return. Reason: Invokers from previous router is empty or conditionRouters is empty. ] Current Node Output: 172.18.111.187:20880,172.18.111.183:20880
          [ AppStateRouter (Input: 2) (Current Node Output: 2) (Chain Node Output: 2) Router message: Directly return. Reason: Invokers from previous router is empty or conditionRouters is empty. ] Current Node Output: 172.18.111.187:20880,172.18.111.183:20880

···

dubbo>

注意：

由于日志框架不匹配导致的日志为空可以参考日志框架适配及运行时管理动态修改日志输出框架。

最后修改 March 2, 2023: Fix alias forward in docs3-v2 (#2342) (f16c1535592)