Slide 13
Slide 13 text
go-kit example
package main
import (
"context"
"encoding/json"
"errors"
"log"
"net/http"
"strings"
"github.com/go-kit/kit/endpoint"
httptransport "github.com/go-kit/kit/transport/http"
)
// StringService provides operations on strings.
type StringService interface {
Uppercase(string) (string, error)
Count(string) int
}
// stringService is a concrete implementation of StringService
type stringService struct{}
func (stringService) Uppercase(s string) (string, error) {
if s == "" {
return "", ErrEmpty
}
return strings.ToUpper(s), nil
}
func (stringService) Count(s string) int {
return len(s)
}
// ErrEmpty is returned when an input string is empty.
var ErrEmpty = errors.New("empty string")
// For each method, we define request and response structs
type uppercaseRequest struct {
S string `json:"s"`
}
type uppercaseResponse struct {
V string `json:"v"`
Err string `json:"err,omitempty"` // errors don't define
JSON marshaling
}
type countRequest struct {
S string `json:"s"`
}
type countResponse struct {
V int `json:"v"`
}
// Endpoints are a primary abstraction in go-kit. An endpoint
represents a single RPC (method in our service interface)
func makeUppercaseEndpoint(svc StringService) endpoint.Endpoint {
return func(_ context.Context, request interface{})
(interface{}, error) {
req := request.(uppercaseRequest)
v, err := svc.Uppercase(req.S)
if err != nil {
return uppercaseResponse{v,
err.Error()}, nil
}
return uppercaseResponse{v, ""}, nil
}
}
func makeCountEndpoint(svc StringService) endpoint.Endpoint {
return func(_ context.Context, request interface{})
(interface{}, error) {
req := request.(countRequest)
v := svc.Count(req.S)
return countResponse{v}, nil
}
}
// Transports expose the service to the network. In this first
example we utilize JSON over HTTP.
func main() {
svc := stringService{}
uppercaseHandler := httptransport.NewServer(
makeUppercaseEndpoint(svc),
decodeUppercaseRequest,
encodeResponse,
)
countHandler := httptransport.NewServer(
makeCountEndpoint(svc),
decodeCountRequest,
encodeResponse,
)
http.Handle("/uppercase", uppercaseHandler)
http.Handle("/count", countHandler)
log.Fatal(http.ListenAndServe(":8080", nil))
}
func decodeUppercaseRequest(_ context.Context, r *http.Request)
(interface{}, error) {
var request uppercaseRequest
if err := json.NewDecoder(r.Body).Decode(&request); err
!= nil {
return nil, err
}
return request, nil
}
func decodeCountRequest(_ context.Context, r *http.Request)
(interface{}, error) {
var request countRequest
if err := json.NewDecoder(r.Body).Decode(&request); err
!= nil {
return nil, err
}
return request, nil
}
func encodeResponse(_ context.Context, w http.ResponseWriter,
response interface{}) error {
return json.NewEncoder(w).Encode(response)
}
Ref.: https://github.com/go-kit/kit/blob/master/examples/stringsvc1/main.go