#gPRC Client for Erlang -- Fast version

---

##DESCRIPTION

This is a fast version of gRPC client implementation for the Erlang programming language.
The so-called fast version is that this gRPC client has used fast http/2 and long connection.

###Base protocol:

• gRPC
• Protocol Buffers

###Dependencies:

• Fast erlang http/2 client
• Protocol Buffers for erlang
• Poolboy

###Author:

• RongCapital(DaLian) information service Ltd.

###Contact us:

• yangdawei@rongcapital.cn
• jinxin@rongcapital.cn
• gaoliang@rongcapital.cn

##HowTo

Refer to:
src/grpc_client.erl
e.g.
#####helloworld.proto

package helloworld;

// The greeting service definition.
service Greeter {
  // Sends a greeting
  rpc SayHello (HelloRequest) returns (HelloReply) {}
}

// The request message containing the user's name.
message HelloRequest {
  string name = 1;
}

// The response message containing the greetings
message HelloReply {
  string message = 1;
}

#####grpc_client.erl

%% gRPC server parameters
-define(GRPC_SERVER_IP, "localhost").
-define(GRPC_SERVER_PORT, 50051).

%% Protocol Buffers parameters
-define(PROTO_FILE_NAME, helloworld).
-define(PROTO_FILE_SERVICE_NAME, 'Greeter').
-define(PROTO_FILE_SERVICE_FUNCTION, 'SayHello').
-define(PROTO_FILE_SERVICE_FUNCTION_PARAMETERS, [{name,"world"}]).

howto_single_conn() ->
	send_request(?GRPC_SERVER_IP, ?GRPC_SERVER_PORT, [
							{module, ?PROTO_FILE_NAME},
							{service,?PROTO_FILE_SERVICE_NAME},
							{function, ?PROTO_FILE_SERVICE_FUNCTION},
							{param, ?PROTO_FILE_SERVICE_FUNCTION_PARAMETERS}]).

%% After how many times reconnect the gRPC connection
-define(RECONNECT_TIMES, 1000).

howto_long_conn() ->
	%% long connection precondition
	lconnect_ets:start(),
	poolManager:start(),
	%% repeat call
	lconnect:post_time(?MODULE, ?GRPC_SERVER_IP, ?GRPC_SERVER_PORT, [
							{module, ?PROTO_FILE_NAME},
							{service,?PROTO_FILE_SERVICE_NAME},
							{function, ?PROTO_FILE_SERVICE_FUNCTION},
							{param, ?PROTO_FILE_SERVICE_FUNCTION_PARAMETERS}],
					   ?RECONNECT_TIMES),	% 1st
	lconnect:post_time(?MODULE, ?GRPC_SERVER_IP, ?GRPC_SERVER_PORT, [
							{module, ?PROTO_FILE_NAME},
							{service,?PROTO_FILE_SERVICE_NAME},
							{function, ?PROTO_FILE_SERVICE_FUNCTION},
							{param, ?PROTO_FILE_SERVICE_FUNCTION_PARAMETERS}],
					   ?RECONNECT_TIMES).	% 2nd

##Build

$ ./rebar get-deps
$ ./rebar compile
$ ./deps/gpb/bin/protoc-erl -I. -o src deps/chatterbox/java-server/src/main/proto/helloworld.proto
$ ./rebar compile

##Run

e.g. ###Run Server -- Precondition -- Javal $ cd deps/chatterbox && ./start-server.sh
#####Notice The first running will take a long time, because need to download gradle and jars.

###Run Client -- Erlang $ ./rebar shell

grpc_client:howto_single_conn().

or

grpc_client:howto_long_conn().

###Use a new proto file $ ./deps/gpb/bin/protoc-erl -I. -o src ${NEW_PROTO_FILE_PATH}
$ ./rebar compile

##Dependencies

The following is the environment of author, may not be mandatory dependencies.

• Linux -- CentOS-7-x86_64-Everything-1503-01
• Erlang -- otp 18.1
• Java -- jdk-8u111-linux-x64
• Gradle -- gradle-2.13 (audo download in start-server.sh)
• Git -- git x86_64 1.8.3.1