Lile is a application generator (think create-react-app, rails new or django startproject) for gRPC services in Go and a set of tools/libraries.

The primary focus of Lile is to remove the boilerplate when creating new services by creating a basic structure, test examples, Dockerfile, Makefile etc.

Lile comes with basic pre setup with pluggable options for things like...

• Metrics (e.g. Prometheus)
• Tracing (e.g. Zipkin)
• PubSub (e.g. Google PubSub)
• Service Discovery

Installing Lile is easy, using go get you can install the cmd line app to generate new services and the required libraries. First you'll need Google's Protocol Buffers installed.

$ brew install protobuf
$ go get -u github.com/lileio/lile/...

• Creating a Service
• Service Definition
• Generating RPC Methods
• Running and Writing Tests
• Using the Generated cmds
• Adding your own cmds

Lile comes with a 'generator' to quickly generate new Lile services.

Lile follows Go's conventions around $GOPATH (see How to Write Go) and is smart enough to parse your new service's name to create the service in the right place.

If your Github username was tessthedog and you wanted to create a new service for posting to Slack you might use the following command.

lile new --name tessthedog/slack

Follow the command line instructions and this will create a new project folder for you with everything you need to continue.

Lile creates gRPC and therefore uses protocol buffers as the language for describing the service methods, the requests and responses.

I highly recommend reading the Google API Design docs for good advice around general naming of RPC methods and messages and how they might translate to REST/JSON, via the gRPC gateway

An example of a service definition can be found in the Lile example project account_service

service AccountService {
  rpc List (ListAccountsRequest) returns (ListAccountsResponse) {}
  rpc GetById (GetByIdRequest) returns (Account) {}
  rpc GetByEmail (GetByEmailRequest) returns (Account) {}
  rpc AuthenticateByEmail (AuthenticateByEmailRequest) returns (Account) {}
  rpc GeneratePasswordToken (GeneratePasswordTokenRequest) returns (GeneratePasswordTokenResponse) {}
  rpc ResetPassword (ResetPasswordRequest) returns (Account) {}
  rpc ConfirmAccount (ConfirmAccountRequest) returns (Account) {}
  rpc Create (CreateAccountRequest) returns (Account) {}
  rpc Update (UpdateAccountRequest) returns (Account) {}
  rpc Delete (DeleteAccountRequest) returns (google.protobuf.Empty) {}
}

By default Lile will create a example RPC method and a simple message for request and response.

syntax = "proto3";
option go_package = "github.com/tessthedog/slack";
package slack;

message Request {
  string id = 1;
}

message Response {
  string id = 1;
}

service Slack {
  rpc Read (Request) returns (Response) {}
}

Let's modify this to be a real service and add our own method.

We're going to create an Announce method that will announce a message to a Slack room.

We're assuming that the Slack team and authentication is already handled by the services configuration, so a user of our service only needs to provide a room and their message. The service is going to send the special Empty response, since we only need to know if an error occurred and don't need to know anything else.

Our proto file now looks like this...

syntax = "proto3";
option go_package = "github.com/tessthedog/slack";
import "google/protobuf/empty.proto";
package slack;

message AnnounceRequest {
  string channel = 1;
  string msg = 2;
}

service Slack {
  rpc Announce (AnnounceRequest) returns (google.protobuf.Empty) {}
}

We now run the protoc tool with our file and the Lile method generator plugin.

protoc -I . slack.proto --lile-server_out=. --go_out=plugins=grpc:$GOPATH/src

Handily, Lile provides a Makefile with each project that has a proto build step already configured. So we can just run that.

make proto

We can see that Lile will create two files for us in the server directory.

$ make proto
protoc -I . slack.proto --lile-server_out=. --go_out=plugins=grpc:$GOPATH/src
2017/07/12 15:44:01 [Creating] server/announce.go
2017/07/12 15:44:01 [Creating test] server/announce_test.go

Let's take a look at the announce.go file that's created for us.

package server

import (
    "errors"

    "github.com/golang/protobuf/ptypes/empty"
    "github.com/tessthedog/slack"
    context "golang.org/x/net/context"
)

func (s SlackServer) Announce(ctx context.Context, r *slack.AnnounceRequest) (*empty.Empty, error) {
  return nil, errors.New("not yet implemented")
}

We can now fill in this generated method with the correct implementation. But let's start with a test!

When you generate an RPC method with Lile a counterpart test file is also created. For example, given our announce.go file, Lile will create announce_test.go in the same directory.

This should look something like the following..

package server

import (
	"testing"

	"github.com/tessthedog/slack"
	"github.com/stretchr/testify/assert"
	context "golang.org/x/net/context"
)

func TestAnnounce(t *testing.T) {
	ctx := context.Background()
	req := &slack.AnnounceRequest{}

	res, err := cli.Announce(ctx, req)
	assert.Nil(t, err)
	assert.NotNil(t, res)
}

You can now run the tests using the Makefile and running make test...

$ make test
=== RUN   TestAnnounce
--- FAIL: TestAnnounce (0.00s)
        Error Trace:    announce_test.go:16
        Error:          Expected nil, but got: &status.statusError{Code:2, Message:"not yet implemented", Details:[]*any.Any(nil)}
        Error Trace:    announce_test.go:17
        Error:          Expected value not to be nil.
FAIL
coverage: 100.0% of statements
FAIL    github.com/tessthedog/slack/server  0.011s
make: *** [test] Error 2

Our test failed because we haven't implemented our method, at the moment we're returning an error of "unimplemented" in our method.

Let's implement the Announce method in announce.go, here's an example using nlopes' slack library.

package server

import (
	"os"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/status"

	"github.com/golang/protobuf/ptypes/empty"
	"github.com/tessthedog/slack"
	sl "github.com/nlopes/slack"
	context "golang.org/x/net/context"
)

var api = sl.New(os.Getenv("SLACK_TOKEN"))

func (s SlackServer) Announce(ctx context.Context, r *slack.AnnounceRequest) (*empty.Empty, error) {
	_, _, err := api.PostMessage(r.Channel, r.Msg, sl.PostMessageParameters{})
	if err != nil {
		return nil, status.Errorf(codes.Internal, err.Error())
	}

	return &empty.Empty{}, nil
}

Let's fill out our testing request and then run our tests again...

package server

import (
	"testing"

	"github.com/tessthedog/slack"
	"github.com/stretchr/testify/assert"
	context "golang.org/x/net/context"
)

func TestAnnounce(t *testing.T) {
	ctx := context.Background()
	req := &slack.AnnounceRequest{
		Channel: "@alex",
		Msg:     "hellooo",
	}

	res, err := cli.Announce(ctx, req)
	assert.Nil(t, err)
	assert.NotNil(t, res)
}

Now if I run the tests with my Slack token as an ENV variable, I should see a passing test!

$ alex@slack: SLACK_TOKEN=zbxkkausdkasugdk make test
go test -v ./... -cover
?       github.com/tessthedog/slack [no test files]
=== RUN   TestAnnounce
--- PASS: TestAnnounce (0.32s)
PASS
coverage: 75.0% of statements
ok      github.com/tessthedog/slack/server  0.331s  coverage: 75.0% of statements
?       github.com/tessthedog/slack/slack   [no test files]
?       github.com/tessthedog/slack/slack/cmd       [no test files]
?       github.com/tessthedog/slack/subscribers     [no test files]

Lile generates a cmd line application based on cobra when you generate your service. You can extend the app with your own cmds or use the built-in cmds to run the service.

Running the cmd line app without any arguments will print the generated help.

For example go run orders/main.go

Running up will run both the RPC server and the pubsub subscribers.

go run orders/main.go up

To add your own cmd, you can use the built in generator from cobra which powers Lile's cmds

$ cd orders
$ cobra add import

You can now edit the file generated to create your cmd, cobra will automatically add the cmd's name to the help.