Hi, community. This issue is related to this [pull request](https://github.com/apache/incubator-dubbo/pull/2228).You can see more details about this feature. A simple and incomplete `TagRouter` has merged into dubbo v2.7.0-snapshot，in this issue，i will introduce what problem did it solve，while i want to refer to your opinion and proposal, decide the final behavior of `TagRouter` .
### What is TagRouter TagRouter is a new implement of Router interface, other exsiting Router : `ConditionRouter`, `ScriptRouter`, `FileRouter`. It makes any request can carry a `request.tag` and any service belong to a certain `tag` Tag will affect the default route behavior. ### Some pain points in the past  fact1: some applications changed at the same time in different branch,like A,B,C. fact2: some applications didn't change ,but deploy repeatedly，like D,E. fact3: if a new feature need to be tested, all 5 application need to be deployed. fact4: isolation by feature is not friendly to parallel development. ### Benefited from tag  we consider the RED，YELLOW，BLUE as **tagged service** , the grey block as origin service or normal service. The benefit we have is that we have reduced a lot of overhead about application deployment. **Only changed applications need deploy incrementally** . ### A vivid example  ### Usage #### consumer ``` RpcContext.getContext().setAttachment("request.tag","red"); ``` I suggest you can use filter or SPI to set this attachment, notice that RpcContext is bound to Thread. #### provider ``` @Bean public ApplicationConfig applicationConfig() { ApplicationConfig applicationConfig = new ApplicationConfig(); applicationConfig.setName("provider-book"); // instruct tag router Map<String,String> parameters = new HashMap<>(); parameters.put(Constants.ROUTER_KEY, "tag"); applicationConfig.setParameters(parameters); return applicationConfig; } ``` ### Need more discussion 1. If a tag request can not find any application of the same tag，should it use other application of different tag (NOTICE : different tag is not the default application with grey block) 2. If a normal request can not find normal application，should it use any tag application?(in my opinion，normal request should not reach the tag application，also the current version). 3. A forceTag flag can be considered to decided the behavior of downgrade. forceTag=true means all tag requests must strictly match the application's tag；forceTag=false means tag requests will prefer the application of the same tag，if there is no corresponding application， downgrade to other application，ignore the tag. 4. On the basis of 3. what is default value of foreTag TRUE or FALSE. more suggestions are welcome to make. [ Full content available at: https://github.com/apache/incubator-dubbo/issues/2341 ] This message was relayed via gitbox.apache.org for [email protected]
