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// Copyright 2022 The OpenZipkin Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package zipkin_test
import (
"log"
"net/http"
"net/http/httptest"
"os"
"time"
"github.com/openzipkin/zipkin-go"
zipkinhttp "github.com/openzipkin/zipkin-go/middleware/http"
logreporter "github.com/openzipkin/zipkin-go/reporter/log"
)
func Example() {
// set up a span reporter
reporter := logreporter.NewReporter(log.New(os.Stderr, "", log.LstdFlags))
defer func() {
_ = reporter.Close()
}()
// create our local service endpoint
endpoint, err := zipkin.NewEndpoint("myService", "localhost:0")
if err != nil {
log.Fatalf("unable to create local endpoint: %+v\n", err)
}
// initialize our tracer
tracer, err := zipkin.NewTracer(reporter, zipkin.WithLocalEndpoint(endpoint))
if err != nil {
log.Fatalf("unable to create tracer: %+v\n", err)
}
// create global zipkin http server middleware
serverMiddleware := zipkinhttp.NewServerMiddleware(
tracer, zipkinhttp.TagResponseSize(true),
)
// create global zipkin traced http client
client, err := zipkinhttp.NewClient(tracer, zipkinhttp.ClientTrace(true))
if err != nil {
log.Fatalf("unable to create client: %+v\n", err)
}
// initialize router
router := http.NewServeMux()
// start web service with zipkin http server middleware
ts := httptest.NewServer(serverMiddleware(router))
defer ts.Close()
// set-up handlers
router.HandleFunc("/some_function", someFunc(client, ts.URL))
router.HandleFunc("/other_function", otherFunc(client))
// initiate a call to some_func
var req *http.Request
req, err = http.NewRequest("GET", ts.URL+"/some_function", nil)
if err != nil {
log.Fatalf("unable to create http request: %+v\n", err)
}
var res *http.Response
res, err = client.DoWithAppSpan(req, "some_function")
if err != nil {
log.Fatalf("unable to do http request: %+v\n", err)
}
_ = res.Body.Close()
// Output:
}
func someFunc(client *zipkinhttp.Client, url string) http.HandlerFunc {
return func(w http.ResponseWriter, r *http.Request) {
log.Printf("some_function called with method: %s\n", r.Method)
// retrieve span from context (created by server middleware)
span := zipkin.SpanFromContext(r.Context())
span.Tag("custom_key", "some value")
// doing some expensive calculations....
time.Sleep(25 * time.Millisecond)
span.Annotate(time.Now(), "expensive_calc_done")
newRequest, err := http.NewRequest("POST", url+"/other_function", nil)
if err != nil {
log.Printf("unable to create client: %+v\n", err)
http.Error(w, err.Error(), 500)
return
}
ctx := zipkin.NewContext(newRequest.Context(), span)
newRequest = newRequest.WithContext(ctx)
var res *http.Response
res, err = client.DoWithAppSpan(newRequest, "other_function")
if err != nil {
log.Printf("call to other_function returned error: %+v\n", err)
http.Error(w, err.Error(), 500)
return
}
_ = res.Body.Close()
}
}
func otherFunc(_ *zipkinhttp.Client) http.HandlerFunc {
return func(w http.ResponseWriter, r *http.Request) {
log.Printf("other_function called with method: %s\n", r.Method)
time.Sleep(50 * time.Millisecond)
}
}
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