/
hello.go
115 lines (97 loc) · 2.82 KB
/
hello.go
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package main
import (
"context"
"encoding/json"
"log"
"net/http"
"net/url"
"strings"
opentracing "github.com/opentracing/opentracing-go"
ottag "github.com/opentracing/opentracing-go/ext"
otlog "github.com/opentracing/opentracing-go/log"
"github.com/PacktPublishing/Mastering-Distributed-Tracing/Chapter04/go/lib/http"
"github.com/PacktPublishing/Mastering-Distributed-Tracing/Chapter04/go/lib/model"
"github.com/PacktPublishing/Mastering-Distributed-Tracing/Chapter04/go/lib/tracing"
)
func main() {
tracer, closer := tracing.Init("go-4-hello")
defer closer.Close()
opentracing.SetGlobalTracer(tracer)
http.HandleFunc("/sayHello/", handleSayHello)
log.Print("Listening on http://localhost:8080/")
log.Fatal(http.ListenAndServe(":8080", nil))
}
func handleSayHello(w http.ResponseWriter, r *http.Request) {
spanCtx, _ := opentracing.GlobalTracer().Extract(
opentracing.HTTPHeaders,
opentracing.HTTPHeadersCarrier(r.Header),
)
span := opentracing.GlobalTracer().StartSpan(
"say-hello",
ottag.RPCServerOption(spanCtx),
)
defer span.Finish()
ctx := opentracing.ContextWithSpan(r.Context(), span)
name := strings.TrimPrefix(r.URL.Path, "/sayHello/")
greeting, err := SayHello(ctx, name)
if err != nil {
span.SetTag("error", true)
span.LogFields(otlog.Error(err))
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
span.SetTag("response", greeting)
w.Write([]byte(greeting))
}
// SayHello creates a greeting for the named person.
func SayHello(ctx context.Context, name string) (string, error) {
person, err := getPerson(ctx, name)
if err != nil {
return "", err
}
return formatGreeting(ctx, person)
}
func getPerson(ctx context.Context, name string) (*model.Person, error) {
url := "http://localhost:8081/getPerson/" + name
res, err := get(ctx, "getPerson", url)
if err != nil {
return nil, err
}
var person model.Person
if err := json.Unmarshal(res, &person); err != nil {
return nil, err
}
return &person, nil
}
func formatGreeting(
ctx context.Context,
person *model.Person,
) (string, error) {
v := url.Values{}
v.Set("name", person.Name)
v.Set("title", person.Title)
v.Set("description", person.Description)
url := "http://localhost:8082/formatGreeting?" + v.Encode()
res, err := get(ctx, "formatGreeting", url)
if err != nil {
return "", err
}
return string(res), nil
}
func get(ctx context.Context, operationName, url string) ([]byte, error) {
req, err := http.NewRequest("GET", url, nil)
if err != nil {
return nil, err
}
span, ctx := opentracing.StartSpanFromContext(ctx, operationName)
defer span.Finish()
ottag.SpanKindRPCClient.Set(span)
ottag.HTTPUrl.Set(span, url)
ottag.HTTPMethod.Set(span, "GET")
opentracing.GlobalTracer().Inject(
span.Context(),
opentracing.HTTPHeaders,
opentracing.HTTPHeadersCarrier(req.Header),
)
return xhttp.Do(req)
}