gRPC-Lua

The Lua gRPC binding.

Dependencies

gRPC-Lua depends on

See doc/conan-graph.html

All these libraries can be installed by conan C/C++ package manager.

Build

Quick Build

Install conan.
Add conan repositories
- conan remote add remote_bintray_conan-community https://api.bintray.com/conan/conan-community/conan
- conan remote add remote_bintray_bincrafters https://api.bintray.com/conan/bincrafters/public-conan
- conan remote add remote_bintray_inexorgame https://api.bintray.com/conan/inexorgame/inexor-conan
- conan remote add remote_bintray_conan https://api.bintray.com/conan/conan/conan-transit
- conan remote add remote_bintray_jinq0123 https://api.bintray.com/conan/jinq0123/test
conan create . user/channel --build missing
- The result grpc_lua.dll/grpc_lua.so is in ~/.conan/data/grpc-lua/0.1/user/channel/package/...

VS solution

See premake/README.md to use premake5 to generate VS solution.

Tutorial

Tutorial shows some codes in the route_guide example.

Define the service

See examples/route_guide/route_guide.proto.

// Interface exported by the server.
service RouteGuide {
  // A simple RPC.
  rpc GetFeature(Point) returns (Feature) {}

  // A server-to-client streaming RPC.
  rpc ListFeatures(Rectangle) returns (stream Feature) {}

  // A client-to-server streaming RPC.
  rpc RecordRoute(stream Point) returns (RouteSummary) {}

  // A Bidirectional streaming RPC.
  rpc RouteChat(stream RouteNote) returns (stream RouteNote) {}
}
...

Import proto file

For both client and server codes:

local grpc = require("grpc_lua.grpc_lua")
grpc.import_proto_file("route_guide.proto")

No need to generate codes.

Client

See examples/route_guide/route_guide_client.lua.

Create a stub

    local c_channel = grpc.channel("localhost:50051")
    local stub = grcp.service_stub(c_channel, "routeguide.RouteGuide")

Call service method

Sync call

Simple RPC: sync_get_feature()

 local feature = stub.sync_request("GetFeature", point(409146138, -746188906))

Server-side streaming RPC: sync_list_features()

 local sync_reader = stub:sync_request_read("ListFeatures", rect)
 while true do
 	local feature = sync_reader.read_one()
 	if not feature then break end
 	print("Found feature: "..inspect(feature))
 end  -- while

Client-side streaming RPC: sync_record_route()

 local sync_writer = stub.sync_request_write("RecordRoute")
 for i = 1, 10 do
 	local feature = db.get_rand_feature()
 	local loc = assert(feature.location)
 	if not sync_writer.write(loc) then
 		break
 	end  -- if
 end  -- for
 
 -- Recv status and reponse.
 local summary, error_str, status_code = sync_writer.close()
 if summary then
 	print_route_sumary(summary)
 end

Bidirectional streaming RPC: sync_route_chat()

 local sync_rdwr = stub.sync_request_rdwr("RouteChat")
 
 for _, note in ipairs(notes) do
 	sync_rdwr.write(note)
 end
 sync_rdwr.close_writing()
 
 -- read remaining
 while true do
 	local server_note = sync_rdwr.read_one()
 	if not server_note then break end
 	print("Got message: "..inspect(server_note))
 end  -- while

Async call

Simple RPC: get_feature_async()

 stub.async_request("GetFeature", point(409146138, -746188906),
 	function(resp)
 		print("Get feature: "..inspect(resp))
 		stub.shutdown()  -- to return
 	end)
 stub.run()  -- run async requests until stub.shutdown()

Ignore response

 stub.async_request("GetFeature", point())  -- ignore response

Set error callback

stub.set_error_cb(function(error_str, status_code) ... end) before async_request()

Run the stub
- Async calls need run()
```
 stub.run()  -- run async requests until stub.shutdown()
```
- stub.shutdown() ends stub.run().

Server-side streaming RPC: list_features_async()

 stub.async_request_read("ListFeatures", rect,
 	function(f)
 		assert("table" == type(f))
 		print(string.format("Got feature %s at %f,%f", f.name,
 			f.location.latitude/kCoordFactor, f.location.longitude/kCoordFactor))
 	end,
 	function(error_str, status_code)
 		assert("number" == type(status_code))
 		stub.shutdown()  -- To break Run().
 	end)
 stub.run()  -- until stub.shutdown()

Client-side streaming RPC: record_route_async()

 local async_writer = stub.async_request_write("RecordRoute")
 for i = 1, 10 do
 	local f = db.get_rand_feature()
 	local loc = f.location
 	if not async_writer:write(loc) do break end  -- Broken stream.
 end  -- for
 
 -- Recv reponse and status.
 async_writer.close(
 	function(resp, error_str, status_code)
 		if resp then
 			print_route_summary(resp)
 		end  -- if
 		stub.shutdown()  -- to break run()
 	end)
 stub.run()  -- until stutdown()

Bidirectional streaming RPC: route_chat_async()

 local rdwr = stub.async_request_rdwr("RouteChat",
 	function(error_str, status_code)
 		stub.shutdown()  -- to break run()
 	end)

 for _, note in ipairs(notes) do
 	rdwr.write(note)
 end
 rdwr.close_writing()  -- Optional.
 rdwr.read_each(function(server_note)
 	assert("table" == type(server_note))
 	print("Got message: "..inspect(server_note))
 end)

 stub.run()  -- until shutdown()

Server

See examples/route_guide/route_guide_server.lua.

Start server

    local svr = grpc.server()
    svr:add_listening_port("0.0.0.0:50051")
    -- Service implementation is a table.
    local service = require("route_guide_service")
    svr:register_service("routeguide.RouteGuide", service)
    svr:run()

Implement service

Service is a table with the service functions defined in the proto file. The function name must be the same as in the proto file. The function parameters are different for different RPC method types.

Simple RPC: GetFeature()

--- Simple RPC method.
-- @tab request
-- @tparam Replier replier
function M.GetFeature(request, replier)
	assert("table" == type(request))
	assert("table" == type(replier))
	local name = get_feature_name(request)
	local response = { name = name, location = request }
	replier:reply(response);
end  -- GetFeature()

replier can be copied and reply() later.

Server-side streaming RPC: ListFeatures()

--- Server-to-client streaming method.
-- @table rectangle
-- @tparam Writer writer
function M.ListFeatures(rectangle, writer)
	assert("table" == type(rectangle))
	assert("table" == type(writer))
	...
	for _, f in ipairs(db.features) do
		local l = f.location
		if l... then
			if not writer.write(f) then
				print("Failed to write.")
				break
			end  -- if not writer.write()
		end  -- if l
	end  -- for _, f
	writer.close()
end  -- ListFeatures()

Client-side streaming RPC: RecordRoute()

Should return a reader table:

 --- Client-to-server streaming method.
 -- @tab replier `Replier` object
 -- @treturn table server reader object
 function M.RecordRoute(replier)
 	assert("table" == type(replier))
 	return require("server_reader.RecordRouteReader"):new(replier, db)
 end  -- RecordRoute()

the reader table should optionally have these methods
- function Reader:on_msg(msg)
- function Reader:on_error(error_str, status_code)
- function Reader:on_end()

Bidirectional streaming RPC: RouteChat()

Should return a reader table.

 --- Bi-directional streaming method.
 -- @table writer `Writer` object
 -- @treturn table server reader object
 function M.RouteChat(writer)
 	assert("table" == type(writer))
 	return require("server_reader.RouteChatReader"):new(writer, db)
 end  -- RouteChat()

The reader table should optionally have methods as client-side streaming reader.

Example codes

How to run examples

Install dependencies into ~/.conan/data using conan install
1. Rename examples/conan_install.bat.example to conan_install.bat
2. Run it.
Copy required exe and dll.
1. Rename examples/copy_from_conan.bat.example to copy_from_conan.bat
2. Change variables in copy_from_conan.bat
  - conandata, conan data dir, default ~/.conan/data
  - package names, conan package names for dependencies
    - lua_cpp_package
    - luapbintf_package
    - grpc_lua_package
3. Run it, which will copy exe and dlls from ~/.conan/data
  - lua-cpp.exe
  - lua-cpp.dll
  - luapbintf.dll
  - grpc_lua.dll
Start lua script
- helloworld
  - lua-cpp.exe greeter_server.lua
  - lua-cpp.exe greeter_client.lua
- route_guide
  - lua-cpp.exe route_guide_server.lua
  - lua-cpp.exe route_guide_client.lua

API doc

See doc/ldoc/html/index.html

TODO: Integrate into Unity

Note: If you are using grpc only as client, grpc-tolua is another option.

I think it is easy to integrate grpc-lua into Unity, but I have no time to do this. Work is:

Use C version of Lua
Support Lua5.1 and LuaJIT
Build for iOS and Android

Unity uses Lua library compiled as C. If use lua.exe and lua.lib compiled as C, C++ objects on stack must be destructed correctly on error. See LuaIntf error handling.

Building with Lua51 or LuaJIT library should succeed. LuaPbIntf, which is used to encode and decode protobuf messages, need to be recompiled with Lua51 or LuaJIT.

jinq0123/grpc-lua

jinq0123

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