feature: Curl like (single request) mode for gRPC

[edieYoung]

Does fortio support curl like (single request) mode for gRPC protocol as well?
I found that grpcping always returns the load test result, can we also support returning a single request result for gRPC?

fortio grpcping -ping -json - http://fortioserver-http:9091
19:41:14 I grpcrunner.go:275> stripping http scheme. grpc destination: fortioserver-http:9091: grpc port: 80
Clock skew histogram usec : count 1 avg -24.082 +/- 0 min -24.082 max -24.082 sum -24.082
# range, mid point, percentile, count
>= -24.082 <= -24.082 , -24.082 , 100.00, 1
# target 50% -24.082
RTT histogram usec : count 3 avg 1570.0523 +/- 200.7 min 1359.14 max 1840.013 sum 4710.157
# range, mid point, percentile, count
>= 1359.14 <= 1400 , 1379.57 , 33.33, 1
> 1400 <= 1600 , 1500 , 66.67, 1
> 1800 <= 1840.01 , 1820.01 , 100.00, 1
# target 50% 1500
19:41:14 I pingsrv.go:151> Ping RTT 1570052 (avg of 1840013, 1511004, 1359140 ns) clock skew -24082

[ldemailly]

if you use health check for grpc and without using -n it should be exactly 1 request?

[edieYoung]

if you use health check for grpc and without using -n it should be exactly 1 request?

yes, but it's still returning the histogram format result. It would be nice if it can return a single request result, e.g. result with a OK status code.

I0202 17:53:59.383458   73811 sh.go:70] running: kubectl --namespace=test-authz exec fortioclient-664f9cd489-dmtg2 --container=fortioclient -- fortio grpcping -health http://fortioserver-grpc.test-authz:8082
RTT histogram usec : count 1 avg 3149.203 +/- 0 min 3149.203 max 3149.203 sum 3149.203
# range, mid point, percentile, count
>= 3149.2 <= 3149.2 , 3149.2 , 100.00, 1
# target 50% 3149.2
Health SERVING : 1

[ldemailly]

I think #589 fixes this (as in the exit status will match the result. lmk if that's not what you want, in which case please describe exactly what you expect)