Implement a two-way pipeline to solve request/response-like scenarios.

e.g.

interface RequestOperation {
    Future invoke(Request request, RpcContext ctx)
}

interface ResponseOperation {
    Future onResponse(Request request, Response response, RpcContext ctx)
}


interface RPCHandler extends RequestOperation, ResponseOperation {
}

after apply @AutoPipeline to RPCHandler (we need to add some metadata for auto-pipeline) :

• invoke method will start from head to tail
• while onResponse will start from tail to head
• may be invoke and onResponse operation will in separate interfaces, and some handler can just implement one of the interfaces
• auto-pipeline will auto detect whether the handler is duplexing or not, and will call or skip the handler adaptively