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package main
import (
"bytes"
"context"
"encoding/json"
"flag"
"fmt"
"io"
"io/ioutil"
"net/http"
"net/url"
"os"
"os/signal"
"strings"
"syscall"
"time"
consulsd "github.com/go-kit/kit/sd/consul"
"github.com/gorilla/mux"
"github.com/hashicorp/consul/api"
stdopentracing "github.com/opentracing/opentracing-go"
stdzipkin "github.com/openzipkin/zipkin-go"
"google.golang.org/grpc"
"github.com/go-kit/kit/endpoint"
"github.com/go-kit/kit/log"
"github.com/go-kit/kit/sd"
"github.com/go-kit/kit/sd/lb"
httptransport "github.com/go-kit/kit/transport/http"
"github.com/go-kit/kit/examples/addsvc/pkg/addendpoint"
"github.com/go-kit/kit/examples/addsvc/pkg/addservice"
"github.com/go-kit/kit/examples/addsvc/pkg/addtransport"
)
func main() {
var (
httpAddr = flag.String("http.addr", ":8000", "Address for HTTP (JSON) server")
consulAddr = flag.String("consul.addr", "", "Consul agent address")
retryMax = flag.Int("retry.max", 3, "per-request retries to different instances")
retryTimeout = flag.Duration("retry.timeout", 500*time.Millisecond, "per-request timeout, including retries")
)
flag.Parse()
// Logging domain.
var logger log.Logger
{
logger = log.NewLogfmtLogger(os.Stderr)
logger = log.With(logger, "ts", log.DefaultTimestampUTC)
logger = log.With(logger, "caller", log.DefaultCaller)
}
// Service discovery domain. In this example we use Consul.
var client consulsd.Client
{
consulConfig := api.DefaultConfig()
if len(*consulAddr) > 0 {
consulConfig.Address = *consulAddr
}
consulClient, err := api.NewClient(consulConfig)
if err != nil {
logger.Log("err", err)
os.Exit(1)
}
client = consulsd.NewClient(consulClient)
}
// Transport domain.
tracer := stdopentracing.GlobalTracer() // no-op
zipkinTracer, _ := stdzipkin.NewTracer(nil, stdzipkin.WithNoopTracer(true))
ctx := context.Background()
r := mux.NewRouter()
// Now we begin installing the routes. Each route corresponds to a single
// method: sum, concat, uppercase, and count.
// addsvc routes.
{
// Each method gets constructed with a factory. Factories take an
// instance string, and return a specific endpoint. In the factory we
// dial the instance string we get from Consul, and then leverage an
// addsvc client package to construct a complete service. We can then
// leverage the addsvc.Make{Sum,Concat}Endpoint constructors to convert
// the complete service to specific endpoint.
var (
tags = []string{}
passingOnly = true
endpoints = addendpoint.Set{}
instancer = consulsd.NewInstancer(client, logger, "addsvc", tags, passingOnly)
)
{
factory := addsvcFactory(addendpoint.MakeSumEndpoint, tracer, zipkinTracer, logger)
endpointer := sd.NewEndpointer(instancer, factory, logger)
balancer := lb.NewRoundRobin(endpointer)
retry := lb.Retry(*retryMax, *retryTimeout, balancer)
endpoints.SumEndpoint = retry
}
{
factory := addsvcFactory(addendpoint.MakeConcatEndpoint, tracer, zipkinTracer, logger)
endpointer := sd.NewEndpointer(instancer, factory, logger)
balancer := lb.NewRoundRobin(endpointer)
retry := lb.Retry(*retryMax, *retryTimeout, balancer)
endpoints.ConcatEndpoint = retry
}
// Here we leverage the fact that addsvc comes with a constructor for an
// HTTP handler, and just install it under a particular path prefix in
// our router.
r.PathPrefix("/addsvc").Handler(http.StripPrefix("/addsvc", addtransport.NewHTTPHandler(endpoints, tracer, zipkinTracer, logger)))
}
// stringsvc routes.
{
// addsvc had lots of nice importable Go packages we could leverage.
// With stringsvc we are not so fortunate, it just has some endpoints
// that we assume will exist. So we have to write that logic here. This
// is by design, so you can see two totally different methods of
// proxying to a remote service.
var (
tags = []string{}
passingOnly = true
uppercase endpoint.Endpoint
count endpoint.Endpoint
instancer = consulsd.NewInstancer(client, logger, "stringsvc", tags, passingOnly)
)
{
factory := stringsvcFactory(ctx, "GET", "/uppercase")
endpointer := sd.NewEndpointer(instancer, factory, logger)
balancer := lb.NewRoundRobin(endpointer)
retry := lb.Retry(*retryMax, *retryTimeout, balancer)
uppercase = retry
}
{
factory := stringsvcFactory(ctx, "GET", "/count")
endpointer := sd.NewEndpointer(instancer, factory, logger)
balancer := lb.NewRoundRobin(endpointer)
retry := lb.Retry(*retryMax, *retryTimeout, balancer)
count = retry
}
// We can use the transport/http.Server to act as our handler, all we
// have to do provide it with the encode and decode functions for our
// stringsvc methods.
r.Handle("/stringsvc/uppercase", httptransport.NewServer(uppercase, decodeUppercaseRequest, encodeJSONResponse))
r.Handle("/stringsvc/count", httptransport.NewServer(count, decodeCountRequest, encodeJSONResponse))
}
// Interrupt handler.
errc := make(chan error)
go func() {
c := make(chan os.Signal)
signal.Notify(c, syscall.SIGINT, syscall.SIGTERM)
errc <- fmt.Errorf("%s", <-c)
}()
// HTTP transport.
go func() {
logger.Log("transport", "HTTP", "addr", *httpAddr)
errc <- http.ListenAndServe(*httpAddr, r)
}()
// Run!
logger.Log("exit", <-errc)
}
func addsvcFactory(makeEndpoint func(addservice.Service) endpoint.Endpoint, tracer stdopentracing.Tracer, zipkinTracer *stdzipkin.Tracer, logger log.Logger) sd.Factory {
return func(instance string) (endpoint.Endpoint, io.Closer, error) {
// We could just as easily use the HTTP or Thrift client package to make
// the connection to addsvc. We've chosen gRPC arbitrarily. Note that
// the transport is an implementation detail: it doesn't leak out of
// this function. Nice!
conn, err := grpc.Dial(instance, grpc.WithInsecure())
if err != nil {
return nil, nil, err
}
service := addtransport.NewGRPCClient(conn, tracer, zipkinTracer, logger)
endpoint := makeEndpoint(service)
// Notice that the addsvc gRPC client converts the connection to a
// complete addsvc, and we just throw away everything except the method
// we're interested in. A smarter factory would mux multiple methods
// over the same connection. But that would require more work to manage
// the returned io.Closer, e.g. reference counting. Since this is for
// the purposes of demonstration, we'll just keep it simple.
return endpoint, conn, nil
}
}
func stringsvcFactory(ctx context.Context, method, path string) sd.Factory {
return func(instance string) (endpoint.Endpoint, io.Closer, error) {
if !strings.HasPrefix(instance, "http") {
instance = "http://" + instance
}
tgt, err := url.Parse(instance)
if err != nil {
return nil, nil, err
}
tgt.Path = path
// Since stringsvc doesn't have any kind of package we can import, or
// any formal spec, we are forced to just assert where the endpoints
// live, and write our own code to encode and decode requests and
// responses. Ideally, if you write the service, you will want to
// provide stronger guarantees to your clients.
var (
enc httptransport.EncodeRequestFunc
dec httptransport.DecodeResponseFunc
)
switch path {
case "/uppercase":
enc, dec = encodeJSONRequest, decodeUppercaseResponse
case "/count":
enc, dec = encodeJSONRequest, decodeCountResponse
default:
return nil, nil, fmt.Errorf("unknown stringsvc path %q", path)
}
return httptransport.NewClient(method, tgt, enc, dec).Endpoint(), nil, nil
}
}
func encodeJSONRequest(_ context.Context, req *http.Request, request interface{}) error {
// Both uppercase and count requests are encoded in the same way:
// simple JSON serialization to the request body.
var buf bytes.Buffer
if err := json.NewEncoder(&buf).Encode(request); err != nil {
return err
}
req.Body = ioutil.NopCloser(&buf)
return nil
}
func encodeJSONResponse(_ context.Context, w http.ResponseWriter, response interface{}) error {
w.Header().Set("Content-Type", "application/json; charset=utf-8")
return json.NewEncoder(w).Encode(response)
}
// I've just copied these functions from stringsvc3/transport.go, inlining the
// struct definitions.
func decodeUppercaseResponse(ctx context.Context, resp *http.Response) (interface{}, error) {
var response struct {
V string `json:"v"`
Err string `json:"err,omitempty"`
}
if err := json.NewDecoder(resp.Body).Decode(&response); err != nil {
return nil, err
}
return response, nil
}
func decodeCountResponse(ctx context.Context, resp *http.Response) (interface{}, error) {
var response struct {
V int `json:"v"`
}
if err := json.NewDecoder(resp.Body).Decode(&response); err != nil {
return nil, err
}
return response, nil
}
func decodeUppercaseRequest(ctx context.Context, req *http.Request) (interface{}, error) {
var request struct {
S string `json:"s"`
}
if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
return nil, err
}
return request, nil
}
func decodeCountRequest(ctx context.Context, req *http.Request) (interface{}, error) {
var request struct {
S string `json:"s"`
}
if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
return nil, err
}
return request, nil
}