2019-05-05 19:14
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发送自定义信号到curreng Golang过程

I'm creating a HTTP server using Go. And whenever I work on a database maintenance, I want the server to redirect all the traffic to "current working on maintenance" page.

Currently, this is done by secret admin page (eg. http://myhome/secret) but I'm wondering if this can be done with signal -similar to TERM signal, but temporarily redirect rather than actually terminate the process.


/home/myhome> nohup startServer &
/home/myhome> changeMyServerStatus "maintenance"

I assume there will be two executable.. "startServer" and "changeMyServerStatus"

So, this is similar to a service. (like reload) But, is this possible? If so, can you give me some hint please?

Thank you

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1条回答 默认 最新

  • ds211107
    ds211107 2019-05-06 14:11

    As noted in the comments, signals may not be the best way to accomplish this. I’m assuming that you do want signals nonetheless.

    You can use the standard user signals: SIGUSR1 to enable maintenance and SIGUSR2 to disable it.

    Use os/signal to get notified of these signals and update program state:

    // Brief example code. Real code might be structured differently
    // (perhaps pack up maint and http.Server in one type MyServer).
    var maint uint32 // atomic: 1 if in maintenance mode
    func handleMaintSignals() {
        ch := make(chan os.Signal, 1)
        go func() { // FIXME: use Server.RegisterOnShutdown to terminate this
            for sig := range ch {
                switch sig { // FIXME: add logging
                case syscall.SIGUSR1:
                    atomic.StoreUint32(&maint, 1)
                case syscall.SIGUSR2:
                    atomic.StoreUint32(&maint, 0)
        signal.Notify(ch, syscall.SIGUSR1, syscall.SIGUSR2)

    Have a middleware look at that state and respond accordingly:

    func withMaint(next http.Handler) http.Handler {
        return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
            if atomic.LoadUint32(&maint) == 1 {
                http.Error(w, "Down for maintenance", http.StatusServiceUnavailable)
            next.ServeHTTP(w, r)

    You can apply this middleware on a per-route basis, or directly to the server’s root handler:

    func main() {
        srv := http.Server{
            Addr:    ":17990",
            Handler: withMaint(http.DefaultServeMux),

    You don’t need a second executable like changeMyServerStatus. Use your operating system’s tools to send signals, such as pkill:

    $ nohup myserver &
    $ curl http://localhost:17990/
    404 page not found
    $ pkill -USR1 myserver
    $ curl http://localhost:17990/
    Down for maintenance
    $ pkill -USR2 myserver
    $ curl http://localhost:17990/
    404 page not found

    But manually juggling nohup and pkill is tedious and error-prone. Instead, use a service manager such as systemd to manage your process. Systemd lets you send arbitrary signals with systemctl kill:

    systemctl kill -s SIGUSR1 myserver
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