Gracefully Shutdown Gorilla Server

Question

I'm building a server in go using gorilla multiplexer library found in https://github.com/gorilla/mux. The problem is, I want it to gracefully shutdown when I'm using Ctrl+C, or when there is a specific API call, for example "/shutdown".

I already know that in Go 1.8, graceful shutdown is already implemented. But how to combine it with gorilla multiplexer? Also, how to combine it with SIGINT signal?

Can anyone show me how to do it?

Answer 1

Channel can be used to capture shutdown request through API call (/shutdown) or interrupt signal (Ctrl+C).

1. Embed http.Server into a custom struct, so we can call http Server.Shutdown later
2. Add channel field (shutdownReq) for passing shutdown request from API call /shutdown
3. Register http handlers including /shutdown in gorilla/mux's router, then assign the router to http.Server.Handler
4. Register os.Interrupt/syscall.SIGINT, syscall.SIGTERM handler
5. Use select to capture shutdown request through API call or interrupt signal
6. Perform clean shutdown by calling Server.Shutdown

Below is the example code:

package main

import (
    "context"
    "log"
    "net/http"
    "sync/atomic"
    "syscall"
    "time"

    "os"
    "os/signal"

    "github.com/gorilla/mux"
)

type myServer struct {
    http.Server
    shutdownReq chan bool
    reqCount    uint32
}

func NewServer() *myServer {
    //create server
    s := &myServer{
        Server: http.Server{
            Addr:         ":8080",
            ReadTimeout:  10 * time.Second,
            WriteTimeout: 10 * time.Second,
        },
        shutdownReq: make(chan bool),
    }

    router := mux.NewRouter()

    //register handlers
    router.HandleFunc("/", s.RootHandler)
    router.HandleFunc("/shutdown", s.ShutdownHandler)

    //set http server handler
    s.Handler = router

    return s
}

func (s *myServer) WaitShutdown() {
    irqSig := make(chan os.Signal, 1)
    signal.Notify(irqSig, syscall.SIGINT, syscall.SIGTERM)

    //Wait interrupt or shutdown request through /shutdown
    select {
    case sig := <-irqSig:
        log.Printf("Shutdown request (signal: %v)", sig)
    case sig := <-s.shutdownReq:
        log.Printf("Shutdown request (/shutdown %v)", sig)
    }

    log.Printf("Stoping http server ...")

    //Create shutdown context with 10 second timeout
    ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
    defer cancel()

    //shutdown the server
    err := s.Shutdown(ctx)
    if err != nil {
        log.Printf("Shutdown request error: %v", err)
    }
}

func (s *myServer) RootHandler(w http.ResponseWriter, r *http.Request) {
    w.Write([]byte("Hello Gorilla MUX!\n"))
}

func (s *myServer) ShutdownHandler(w http.ResponseWriter, r *http.Request) {
    w.Write([]byte("Shutdown server"))

    //Do nothing if shutdown request already issued
    //if s.reqCount == 0 then set to 1, return true otherwise false
    if !atomic.CompareAndSwapUint32(&s.reqCount, 0, 1) {
        log.Printf("Shutdown through API call in progress...")
        return
    }

    go func() {
        s.shutdownReq <- true
    }()
}

func main() {
    //Start the server
    server := NewServer()

    done := make(chan bool)
    go func() {
        err := server.ListenAndServe()
        if err != nil {
            log.Printf("Listen and serve: %v", err)
        }
        done <- true
    }()

    //wait shutdown
    server.WaitShutdown()

    <-done
    log.Printf("DONE!")
}

Note: Please watch this issue which is related to gracefull shutdown.