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slides/README.md

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+# [fit] Protobuf & Code Generation
+
+### 2016, by Manfred Touron (@moul)
+
+---
+
+# overview
+
+* go-kit is an amazing framework to develop strong micro services
+* but it requires a lot of boilerplate code
+* return on experience on go-kit boilerplate code generation
+
+---
+
+# protobuf?
+
+* limited to exchanges (methods and models)
+* extendable with plugins
+* contract-based
+* universal
+
+---
+
+# code generation?
+
+* the good old ./generate.sh bash script
+* go:generate
+* make
+* protobuf + [protoc-gen-gotemplate](https://github.com/moul/protoc-gen-gotemplate)
+
+---
+
+# go-kit
+
+* protobuf-first, rpc-first service framework in Golang
+* abstract services, endpoints, transports
+* requires a lot of boilerplate code in multiple packages
+
+---
+
+# example: `session.proto`
+
+```protobuf
+syntax = "proto3";
+package session;
+
+service SessionService {
+  rpc Login(LoginRequest) returns (LoginResponse) {}
+}
+
+message LoginRequest {
+  string username = 1;
+  string password = 2;
+}
+
+message LoginResponse {
+  string token = 1;
+  string err_msg = 2;
+}
+```
+
+---
+
+# example: `session.go`
+
+```go
+package sessionsvc
+
+import (
+	"fmt"
+	"golang.org/x/net/context"
+	pb "github.com/moul/protoc-gen-gotemplate/examples/go-kit/services/session/gen/pb"
+)
+
+type Service struct{}
+
+func New() pb.SessionServiceServer {
+	return &Service{}
+}
+
+func (svc *Service) Login(ctx context.Context, in *pb.LoginRequest) (*pb.LoginResponse, error) {
+    // custon code here
+	return nil, fmt.Errorf("not implemented")
+}
+```
+
+---
+
+##### example: `{{.File.Package}}/gen/transports/http/http.go.tmpl`
+
+```go
+// source: templates/{{.File.Package}}/gen/transports/http/http.go.tmpl
+package {{.File.Package}}_httptransport
+import (
+    gokit_endpoint "github.com/go-kit/kit/endpoint"
+	httptransport "github.com/go-kit/kit/transport/http"
+	endpoints "github.com/moul/protoc-gen-gotemplate/examples/go-kit/services/{{.File.Package}}/gen/endpoints"
+	pb "github.com/moul/protoc-gen-gotemplate/examples/go-kit/services/{{.File.Package}}/gen/pb"
+)
+```
+
+```go
+// result: services/user/gen/transports/http/http.go
+package user_httptransport
+import (
+	gokit_endpoint "github.com/go-kit/kit/endpoint"
+	httptransport "github.com/go-kit/kit/transport/http"
+	endpoints "github.com/moul/protoc-gen-gotemplate/examples/go-kit/services/user/gen/endpoints"
+	pb "github.com/moul/protoc-gen-gotemplate/examples/go-kit/services/user/gen/pb"
+)
+```
+
+---
+
+##### example: `{{.File.Package}}/gen/transports/http/http.go.tmpl`
+
+```go
+// source: templates/{{.File.Package}}/gen/transports/http/http.go.tmpl
+{{range .Service.Method}}
+func Make{{.Name}}Handler(ctx context.Context, svc pb.{{$file.Package | title}}ServiceServer, endpoint gokit_endpoint.Endpoint) *httptransport.Server {
+	return httptransport.NewServer(
+		ctx,
+		endpoint,
+		decode{{.Name}}Request,
+		encode{{.Name}}Response,
+                []httptransport.ServerOption{}...,
+	)
+}
+{{end}}
+```
+
+```go
+// result: services/user/gen/transports/http/http.go
+func MakeGetUserHandler(ctx context.Context, svc pb.UserServiceServer, endpoint gokit_endpoint.Endpoint) *httptransport.Server {
+	return httptransport.NewServer(
+		ctx,
+		endpoint,
+		decodeGetUserRequest,
+		encodeGetUserResponse,
+		[]httptransport.ServerOption{}...,
+	)
+}
+```
+
+---
+
+##### example: `{{.File.Package}}/gen/transports/http/http.go.tmpl`
+
+```go
+// source: templates/{{.File.Package}}/gen/transports/http/http.go.tmpl
+func RegisterHandlers(ctx context.Context, svc pb.{{$file.Package | title}}ServiceServer, mux *http.ServeMux, endpoints endpoints.Endpoints) error {
+	{{range .Service.Method}}
+        log.Println("new HTTP endpoint: \"/{{.Name}}\" (service={{$file.Package | title}})")
+	mux.Handle("/{{.Name}}", Make{{.Name}}Handler(ctx, svc, endpoints.{{.Name}}Endpoint))
+	{{end}}
+	return nil
+}
+```
+
+```go
+// result: services/user/gen/transports/http/http.go
+func RegisterHandlers(ctx context.Context, svc pb.UserServiceServer, mux *http.ServeMux, endpoints endpoints.Endpoints) error {
+
+	log.Println("new HTTP endpoint: \"/CreateUser\" (service=User)")
+	mux.Handle("/CreateUser", MakeCreateUserHandler(ctx, svc, endpoints.CreateUserEndpoint))
+
+	log.Println("new HTTP endpoint: \"/GetUser\" (service=User)")
+	mux.Handle("/GetUser", MakeGetUserHandler(ctx, svc, endpoints.GetUserEndpoint))
+
+	return nil
+}
+```
+
+---
+
+#### `protoc --gogo_out=plugins=grpc:. ./services/*/*.proto`
+
+---
+
+#### `protoc --gotemplate_out=template_dir=./templates:services ./services/*/*.proto`
+
+---
+
+![fit](assets/session-wc.png)
+
+---
+
+![right fit](assets/wc.png)
+
+## 3 services
+## 6 methods
+## 149 custom lines
+## 1429 generated lines
+## business focus
+
+---
+
+# generation usages
+
+* go-kit boilerplate (see [examples/go-kit](https://github.com/moul/protoc-gen-gotemplate/tree/master/examples/go-kit))
+* k8s configuration
+* Dockerfile
+* documentation
+* unit-tests
+* fun
+
+---
+
+# pros
+
+* small custom codebase
+* templates shipped with code
+* hardly typed, no reflects
+* genericity
+* contrat terms (protobuf) respected
+* not limited to a language
+
+---
+
+# cons
+
+* the author needs to write its own templates
+* sometimes difficult to generate valid code
+* not enough helpers around the code generation yet
+
+---
+
+# improvement ideas
+
+* Support protobufs extensions (i.e, annotations.probo)
+* Generate one file from multiple services
+* Add more helpers around the code generation
+
+---
+
+# conclusion
+
+* Useful to keep everything standard
+* The awesomeness of go-kit without the hassle of writing boilerplate code
+* Always up-to-date with the contracts
+
+---
+
+# questions?
+
+### github.com/moul/protoc-gen-gotemplate
+### @moul