[GitHub] [skywalking] liudantop opened a new issue #2637: pring MVC/Tomcat plugin can not output tracing data if current request is forward request.

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liudantop opened a new issue #2637: pring MVC/Tomcat plugin can not output tracing data if current request is forward request.
URL: https://github.com/apache/skywalking/issues/2637
 
 
   Please answer these questions before submitting your issue.
   
   - Why do you submit this issue?
   - [ ] Question or discussion
   - [ 1] Bug
   - [ ] Requirement
   - [ ] Feature or performance improvement
   
   ___
   ### Question
   - What do you want to know?
   
   ___
   ### Bug
   - Which version of SkyWalking, OS and JRE?
   6.1.0
   Jdk8
   win10
   Springboot 1.5
   - Which company or project?
   
   - What happen?
   If possible, provide a way for reproducing the error. e.g. demo application, component version.
   In scenario:
   1.have a API "/test_forward"
   2.API "/test_forward" mapping method will forward to the URL "/error_proto"
   
   It can not generate tracing span data.
   
   demo code:
   import javax.servlet.RequestDispatcher;
   import javax.servlet.ServletException;
   import javax.servlet.http.HttpServletRequest;
   import javax.servlet.http.HttpServletResponse;
   import java.io.IOException;
   
   @RestController
   public class Rest02 {
       @GetMapping("/test_forward")
       public void test_forward(HttpServletRequest request,
                                HttpServletResponse response) {
           RequestDispatcher dispatcher = request.getRequestDispatcher("/error_test");
           try {
               dispatcher.forward(request, response);
           } catch (ServletException e) {
               e.printStackTrace();
           } catch (IOException e) {
               e.printStackTrace();
           }
       }
   
       @GetMapping("/error_test")
       public String error_proto(){
           return "error test";
       }
   }
   
   
   debug agent stack:
   I find that activeSpanStack is not empty in TracingContext, becuase step6 direct return, then stackDepth = 1 in step7 stopSpan,  so it can not finsh:
   1: TomcatInvokeInterceptor(tomcat plugin) > before method
   -----2: AbstractMethodInterceptor(spring plugin) > before method
   ----------3: ForwardInterceptor(tomcat) > before(set forward flag)
   ---------------4: AbstractMethodInterceptor > before method(because forward flag then return )
   ---------------5: AbstractMethodInterceptor > after method(because forward flag then return )
   -----6: AbstractMethodInterceptor > after method(because forward flag then return )
   7: TomcatInvokeInterceptor(tomcat plugin) > after method
   
   ___
   ### Requirement or improvement
   - Please describe about your requirements or improvement suggestions.

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