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