/
backend.go
42 lines (36 loc) · 1.32 KB
/
backend.go
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// Copyright 2021 Sheldon Lobo
//
// 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 handler
import (
"fmt"
"github.com/openzipkin/zipkin-go"
"log"
"net/http"
"time"
)
func BackendHandler() http.HandlerFunc {
return func(w http.ResponseWriter, r *http.Request) {
log.Println("Received backend request to:", r.Host, r.URL.Path, "::", r.Method)
// retrieve span from context (created by server middleware)
span := zipkin.SpanFromContext(r.Context())
span.Tag("backend_key", "backend value")
// doing some expensive calculations....
time.Sleep(25 * time.Millisecond)
span.Annotate(time.Now(), "backend expensive_calc_done")
time.Sleep(25 * time.Millisecond)
w.WriteHeader(http.StatusOK)
responseBody := fmt.Sprintf("From backend: %s", time.Now().Local().Format("15:04:05.000"))
w.Write([]byte(responseBody))
}
}