[GitHub] gougouzcm opened a new issue #1622: Can the dubbo router be more customized

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gougouzcm opened a new issue #1622: Can the dubbo router be more customized  
URL: https://github.com/apache/incubator-dubbo/issues/1622
 
 
   I want to use the feature  [1438](https://github.com/apache/incubator-dubbo/pull/1438)，
   But the code seem has not been merge to master.
   By the way ,I think the lable  `<dubbo:provider unit="anything"/>`  may not be that useful for ABtest.
   The lable must write in xml and can not change dynamic.
   
   The most common situation is ConsumerA --->  ProviderA ，then ProviderA  get a error .
   Now I fix the bug and want to verify it ,So I startup a addition ProviderA (I call it providerAPlus).
   The normal requests ( I mean the not verify request for this fix ) should not access to ProviderAPlus, 
   But when I want the request ( from developers )access ProviderAPlus ，I don't want to restart the ConsumerA and add   `<dubbo:provider unit="test"/>`  in the xml or startup a consumerAPlus,
   Then the nginx help me to send the request from app/html to ConsumerAPlus( via cookie  or header).
   
   The perfect solution is I startup the ProviderAPlus ( which xml contails `<dubbo:provider unit="test"/> )
   Then request from APP/html first come into a httpFilter( I call it ABtestFilter), In the filter I judge  if the current request is a testRequest via cooike/header。 The I set something in ThreadLocal . 
   The the dubbo give me a way like  `<dubbo:provider groupRouter="test"/>` as a SPI .
   see  [AbstractDirectory.java](https://github.com/apache/incubator-dubbo/blob/master/dubbo-cluster/src/main/java/com/alibaba/dubbo/rpc/cluster/directory/AbstractDirectory.java)
   In the method 
   ```
   1. protected void setRouters(List<Router> routers) {
   2.         // copy list
   3.         routers = routers == null ? new ArrayList<Router>() : new ArrayList<Router>(routers);
   4.         // append url router
   5.         String routerkey = url.getParameter(Constants.ROUTER_KEY);
   6.         if (routerkey != null && routerkey.length() > 0) {
   7.             RouterFactory routerFactory = ExtensionLoader.getExtensionLoader(RouterFactory.class).getExtension(routerkey);
   8.             routers.add(routerFactory.getRouter(url));
   9.         }
   10.         // append mock invoker selector
   11.         routers.add(new MockInvokersSelector());
   12.         Collections.sort(routers);
   13.         this.routers = routers;
   14.     }
   
   ```
   In my custom spi router , I can read the variable in ThreadLocal I put when the request come into httpFilter .  So I know it is a test request from developers ,I will route it to providerAPlus.
   
   The advantage ：
      I don't need to startup a ConsumerAPlus  or  change the xml in ConsumerA the restart ConsumerA  
   
   The advice I said may too customized  But In the actual production environment , It really a common question 
   
   By the way ,I want to know when the next version can be publisher ,I want to use the feature  [1438](https://github.com/apache/incubator-dubbo/pull/1438)
   
   can any one help me . thk.
   

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