NATS transport

examples/stringsvc4/main.go

@@ -0,0 +1,206 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"log"
+	"strings"
+	"flag"
+	"net/http"
+
+	"github.com/go-kit/kit/endpoint"
+	natstransport "github.com/go-kit/kit/transport/nats"
+	httptransport "github.com/go-kit/kit/transport/http"
+
+	"github.com/nats-io/go-nats"
+)
+
+// StringService provides operations on strings.
+type StringService interface {
+	Uppercase(context.Context, string) (string, error)
+	Count(context.Context, string) int
+}
+
+// stringService is a concrete implementation of StringService
+type stringService struct{}
+
+func (stringService) Uppercase(_ context.Context, s string) (string, error) {
+	if s == "" {
+		return "", ErrEmpty
+	}
+	return strings.ToUpper(s), nil
+}
+
+func (stringService) Count(_ context.Context, 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 makeUppercaseHTTPEndpoint(nc *nats.Conn) endpoint.Endpoint {
+	return natstransport.NewPublisher(
+		nc,
+		"stringsvc.uppercase",
+		natstransport.EncodeJSONRequest,
+		decodeUppercaseResponse,
+	).Endpoint()
+}
+
+func makeCountHTTPEndpoint(nc *nats.Conn) endpoint.Endpoint {
+	return natstransport.NewPublisher(
+		nc,
+		"stringsvc.count",
+		natstransport.EncodeJSONRequest,
+		decodeCountResponse,
+	).Endpoint()
+}
+
+func makeUppercaseEndpoint(svc StringService) endpoint.Endpoint {
+	return func(ctx context.Context, request interface{}) (interface{}, error) {
+		req := request.(uppercaseRequest)
+		v, err := svc.Uppercase(ctx, req.S)
+		if err != nil {
+			return uppercaseResponse{v, err.Error()}, nil
+		}
+		return uppercaseResponse{v, ""}, nil
+	}
+}
+
+func makeCountEndpoint(svc StringService) endpoint.Endpoint {
+	return func(ctx context.Context, request interface{}) (interface{}, error) {
+		req := request.(countRequest)
+		v := svc.Count(ctx, req.S)
+		return countResponse{v}, nil
+	}
+}
+
+// Transports expose the service to the network. In this fourth example we utilize JSON over NATS and HTTP.
+func main() {
+	svc := stringService{}
+
+	natsURL := flag.String("nats-url", nats.DefaultURL, "URL for connection to NATS")
+	flag.Parse()
+
+	nc, err := nats.Connect(*natsURL)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer nc.Close()
+
+	uppercaseHTTPHandler := httptransport.NewServer(
+		makeUppercaseHTTPEndpoint(nc),
+		decodeUppercaseHTTPRequest,
+		httptransport.EncodeJSONResponse,
+	)
+
+	countHTTPHandler := httptransport.NewServer(
+		makeCountHTTPEndpoint(nc),
+		decodeCountHTTPRequest,
+		httptransport.EncodeJSONResponse,
+	)
+
+	uppercaseHandler := natstransport.NewSubscriber(
+		makeUppercaseEndpoint(svc),
+		decodeUppercaseRequest,
+		natstransport.EncodeJSONResponse,
+	)
+
+	countHandler := natstransport.NewSubscriber(
+		makeCountEndpoint(svc),
+		decodeCountRequest,
+		natstransport.EncodeJSONResponse,
+	)
+
+	uSub, err := nc.QueueSubscribe("stringsvc.uppercase", "stringsvc", uppercaseHandler.ServeMsg(nc))
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer uSub.Unsubscribe()
+
+	cSub, err := nc.QueueSubscribe("stringsvc.count", "stringsvc", countHandler.ServeMsg(nc))
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer cSub.Unsubscribe()
+
+	http.Handle("/uppercase", uppercaseHTTPHandler)
+	http.Handle("/count", countHTTPHandler)
+	log.Fatal(http.ListenAndServe(":8080", nil))
+
+}
+
+func decodeUppercaseHTTPRequest(_ 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 decodeCountHTTPRequest(_ 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 decodeUppercaseResponse(_ context.Context, msg *nats.Msg) (interface{}, error) {
+	var response uppercaseResponse
+
+	if err := json.Unmarshal(msg.Data, &response); err != nil {
+		return nil, err
+	}
+
+	return response, nil
+}
+
+func decodeCountResponse(_ context.Context, msg *nats.Msg) (interface{}, error) {
+	var response countResponse
+
+	if err := json.Unmarshal(msg.Data, &response); err != nil {
+		return nil, err
+	}
+
+	return response, nil
+}
+
+func decodeUppercaseRequest(_ context.Context, msg *nats.Msg) (interface{}, error) {
+	var request uppercaseRequest
+
+	if err := json.Unmarshal(msg.Data, &request); err != nil {
+		return nil, err
+	}
+	return request, nil
+}
+
+func decodeCountRequest(_ context.Context, msg *nats.Msg) (interface{}, error) {
+	var request countRequest
+
+	if err := json.Unmarshal(msg.Data, &request); err != nil {
+		return nil, err
+	}
+	return request, nil
+}
+

transport/nats/doc.go

@@ -0,0 +1,2 @@
+// Package nats provides a NATS transport.
+package nats

transport/nats/encode_decode.go

@@ -0,0 +1,32 @@
+package nats
+
+import (
+	"context"
+
+	"github.com/nats-io/go-nats"
+)
+
+// DecodeRequestFunc extracts a user-domain request object from a publisher
+// request object. It's designed to be used in NATS subscribers, for subscriber-side
+// endpoints. One straightforward DecodeRequestFunc could be something that
+// JSON decodes from the request body to the concrete response type.
+type DecodeRequestFunc func(context.Context, *nats.Msg) (request interface{}, err error)
+
+// EncodeRequestFunc encodes the passed request object into the NATS request
+// object. It's designed to be used in NATS publishers, for publisher-side
+// endpoints. One straightforward EncodeRequestFunc could something that JSON
+// encodes the object directly to the request payload.
+type EncodeRequestFunc func(context.Context, *nats.Msg, interface{}) error
+
+// EncodeResponseFunc encodes the passed response object to the subscriber reply.
+// It's designed to be used in NATS subscribers, for subscriber-side
+// endpoints. One straightforward EncodeResponseFunc could be something that
+// JSON encodes the object directly to the response body.
+type EncodeResponseFunc func(context.Context, string, *nats.Conn, interface{}) error
+
+// DecodeResponseFunc extracts a user-domain response object from an NATS
+// response object. It's designed to be used in NATS publisher, for publisher-side
+// endpoints. One straightforward DecodeResponseFunc could be something that
+// JSON decodes from the response payload to the concrete response type.
+type DecodeResponseFunc func(context.Context, *nats.Msg) (response interface{}, err error)
+