health_service.go

/*
 * Copyright (C) 2021 Orange & contributors
 *
 * This program is free software; you can redistribute it and/or modify it under the terms
 *
 * of the GNU Lesser General Public License as published by the Free Software Foundation;
 * either version 3 of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
 * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License along with this
 * program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth
 * Floor, Boston, MA  02110-1301, USA.
 */

package internal

import (
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"strings"
	"time"
)

type healthResponse struct {
	Status string `json:"status"`
}

const readHeaderTimeout = 2 * time.Second

func serverHandler(writer http.ResponseWriter, request *http.Request) {
	if strings.ToUpper(request.Method) != "GET" {
		http.Error(writer, "Method not allowed", http.StatusMethodNotAllowed)
	} else if request.URL.Path != "/health" {
		http.Error(writer, fmt.Sprintf("Not found: %s", request.RequestURI), http.StatusNotFound)
	} else {
		health(writer, request)
	}
}

func health(writer http.ResponseWriter, request *http.Request) {
	body, err := json.Marshal(healthResponse{Status: "OK"})
	if err != nil {
		http.Error(writer, err.Error(), http.StatusInternalServerError)
		return
	}
	writer.Header().Set("Content-Type", "application/json")
	writer.WriteHeader(http.StatusOK)
	if _, err = writer.Write(body); err != nil {
		panic("Error while sending response in health")
	}
}

func HealthService(port int) (error, *http.Server) {
	log.Printf("Starting application on port %d\n", port)
	server := &http.Server{
		Addr:              fmt.Sprintf(":%d", port),
		Handler:           http.HandlerFunc(serverHandler),
		ReadHeaderTimeout: readHeaderTimeout,
	}
	return server.ListenAndServe(), server
}