Build Event Service

[Jiayi Guo]

Hi,

(I am new to Bazel and Grpc)

In my understanding, the BazelEventServiceClient is using an asynchronous stub to make calls to the server to send the request of the build event (PublishBuildToolEventStreamRequest). 

However,  in the publishBuildEvents() method in BuildEventServiceUploader.java which manages the interaction between the client and the server, we can see that ACKs are expected to be received and in the correct order for every build event sent by the client. Then what is the purpose of an asynchronous stub, isn't it just a synchronous task? 

Does that also mean that we can always expect the build events to come in the same order every time clients send build events to the server? In that case, do we even need to consider implementing a thread-safe server?

I hope it was not too much, thanks!