Lost context in @Blocking gRPC Service behind a GlobalInterceptor

[spencercjh]

I found that Quarkus Server register io.quarkus.grpc.runtime.supports.blocking.BlockingServerInterceptor for each blocking gRPC service with the @Blocking annotation before it starts.

If some global interceptors (with @GlobalInterceptor) set the Context value will not work. The Context will still be empty in the actual rpc method handler.

Is it a normal phenomenon because Context should be placed after BlockingServerInterceptor 's vert.x.executeBlocking? There are some associated issues: #14665, #13959.

Finally, I replace the @GlobalInterceptor with @RegisterInterceptor(MyInterceptor.class), and everything is to be ok which seems to prove my point.

I don't particularly understand the technical details of it, and these are what I got from trying and debugging. I've been only using Spring and Micronaut before.

origin question:

https://stackoverflow.com/questions/73039706/lost-context-in-blocking-grpc-service-with-quarkus-behind-a-globalinterceptor

[quarkus-bot]

/cc @cescoffier, @michalszynkiewicz

[spencercjh]

If my description is correct, I would like to add the above to the relevant docs(gRPC interceptor, @Blocking) with a PR.

[cescoffier]

@spencercjh sorry for the delay.
By any chance, do you have a reproducer?

[cescoffier]

I was able to reproduce it.

[spencercjh]

@cescoffier sorry for the delay...

                                                                                                                                                        
                                                                                                                                                             
                                                                                                                                                             
                                                                                                                                                             
                                     Global gRPC interceptor      vert.x BlockingServerInterceptor   Actual request handler                                  
                                             +----+                           +----+                         +----+                                          
                                             |    |                           |    |                         |    |                                          
                                  request    |    |                           |    |                         |    |                                          
                        -------------------->|    | ------------------------->|    |-----------------------> |    |---------+                                
                                             |    |                           |    |                         |    |         |                                
                                             |    |                           |    |                         |    |         | process                        
                                             |    |                           |    |                         |    |         |                                
                                             |    |                           |    |                         |    |         v                                
                                             |    |                        -->|    | <---------------------- |    |<---------                                
                                             +----+                    ---/   +----+    throw exception      +----+                                          
                                                      hang up here  --/                                                                                      
                                                      and no response to stub becasue  onError isn't invoked.                                                
                                                                                                                       

The best practice for gRPC is to use the Global gRPC Interceptor to handle exceptions as a last resort, but due to the problems mentioned in this issue, this operation is not feasible (under @Blocking gRPC), the thread will hang, the request will not be responded to correctly, and the code will not run to the interceptor as expected.

I actually wanted to write the gRPC service with the asynchronous API that Quarkus recommends more, but the gRPC and Protobuf we use are managed by Buf, not just pure protoc, so we can't generate a whole new set of gRPC code like in the documentation.

Maybe we need another issue to discuss the global interceptor order under @Blocking.