在go http处理程序中使用goroutine和channel使ResponseWriter被阻止

Question

package main

import (
    "fmt"
    "log"
    "net/http"
    "time"
)

var ch chan bool

func testTimer1() {
    go func() {
        log.Println("test timer 1")
        ch <- true
    }()

}

func timer1() {
    timer1 := time.NewTicker(2 * time.Second)
    select {
    case <-timer1.C:
        testTimer1()
    }

}

func myhandler(w http.ResponseWriter, r *http.Request) {
    for {
        go timer1()

        a := <-ch
        log.Println("get a: ", a)
        fmt.Fprintf(w, "hello world!!!!", a)
    }

    log.Println("test for break")
}

func main() {
    ch = make(chan bool)
    http.HandleFunc("/", myhandler)
    http.ListenAndServe(":8080", nil)
}

I wrote the above code, put a channel into "myhandler", channel will be given a bool data when the

timer task executed.

then I get the data from channel and write "hello world" into http writer

but I found the client couldn't receive the "hello world", the writer has been blocked!!!!!

Any one knows about this?

looks the running pic on my cmd: enter image description here

enter image description here

Answer 1

The for loop is an infinite loop so printing to the ResponseWriter is not "scheduled" to happen. If you want a comet-like approack (or long-polling URL) you may want to try this method.

There's also a leak of tickers in timer1(). According to the Go Docs:

Stop the ticker to release associated resources.

You're always creating a new ticker every time you call go timer1() and the ticker is never closed so every new ticker just adds-up.