does grpc service must have exactly one input parameter and one return value -

let's have proto file this. can define service this

rpc sayhello () returns (response) {} //service has no input rpc sayhello (request1,request2) returns (response) {}//service has 2 inputs 

//.proto file

syntax = "proto3";  service greeter{     rpc sayhello (request) returns (response) {} }   message request{     string request = 1; }  message response{     string response = 1; } 

grpc service methods have 1 input message , 1 output message. typically, these messages used input , output only one method. on purpose, allows adding new parameters later (to messages) while maintaining backward compatibility.

if don't want input or output parameters, can use well-known proto google.protobuf.empty. however, discouraged prevents adding parameters method in future. instead, encouraged follow normal practice of having message request, no contents:

service greeter {     rpc sayhello (sayhellorequest) returns (sayhelloresponse) {} }  message sayhellorequest {} // service has no input 

similarly, if want 2 request parameters, include both in request message:

message sayhellorequest { // service has 2 inputs     string request = 1;     string anotherrequestparam = 2; }