etcd http/grpc performance testing

What is the difference in the efficiency of accessing etcd with http and grpc respectively?

We use below client programs to do the test:

1. http go-http, access etcd grpc gateway, http keepalive enabled
2. grpc go-etcd

# http put
go run http.go -c 10 -n 8000 -host http://httpbin.local:2379 -put

# grpc put
go run grpc.go -c 10 -n 8000 -host http://httpbin.local:2379 -put

# you could watch the connections to etcd
watch -n 3 "ss -tnp '( dport = :2379 )' | sort -k6"

# http watch
# in terminal-1
go run http.go -c 10 -n 8000 -host http://httpbin.local:2379 -watch
# in terminal-2, raise traffic to watch
go run grpc.go -c 10 -n 8000 -host http://httpbin.local:2379 -put

# grpc watch
# in terminal-1
go run grpc.go -c 10 -n 8000 -host http://httpbin.local:2379 -watch
# in terminal-2, raise traffic to watch
go run grpc.go -c 10 -n 8000 -host http://httpbin.local:2379 -put

• watch performance is almost the same, because http uses only one tcp connection and chunked streaming for receiving watch events.
• put performance, grpc is about 13% better than http, and the cpu of etcd server is smaller than grpc client.
  • http uses multiple tcp connections, because http/1.1 cannot multiplex requests
  • http has bigger size of packets than grpc (http/2)
  • etcd uses grpc-gateway to bridge the traffic between http and grpc internally