fatal error: concurrent map writes

[xtony77]

If set the handler time.Sleep same as the timeout, there is a chance to reproduce this error!

api.GET("/test", timeout.New(
			timeout.WithTimeout(200*time.Microsecond),
			timeout.WithHandler(func(c *gin.Context) {
				time.Sleep(200*time.Microsecond)
				c.JSON(http.StatusOK, gin.H{
					"code": 200,
					"data": "",
				})
			}),
			timeout.WithResponse(func(c *gin.Context) {
				c.JSON(http.StatusRequestTimeout, gin.H{
					"code":    "408",
					"message": "test",
				})
			}),
		))

Here is gin panic code line:
https://github.com/gin-gonic/gin/blob/580e7da6eed01e2926de1240ec31f6473cd1a2af/render/render.go#L38

There is also a chance of combined http results:

{
    "code": 200,
    "data": ""
}{
    "code": "408",
    "message": "test"
}

I can't think of a solution at the moment, does anyone have any good ideas?

[appleboy]

What is your version?

[xtony77]

github.com/gin-contrib/timeout v0.0.3-0.20220106074521-2cfe50edf125
github.com/gin-gonic/gin v1.7.2

[appleboy]

@xtony77 I can't reproduce the issue

[xtony77]

I tried a few more times and still have a chance to reproduce the problem!
As you can see in the screenshot, although the http status code is 408, the http result is merged.

github.com/gin-gonic/gin v1.8.1
github.com/gin-contrib/timeout v0.0.3

[appleboy]

@xtony77 OK. I will take a look.

[KuanYuLai]

I was able to reproduce the bug but the chance is very rare for me. However, when I change the sleep duration of the code: 200 response, the chance to produce the fatal error: concurrent map writes error is higher.

Code:

	r.GET("/timeout", timeout.New(timeout.WithTimeout(200*time.Microsecond),
		timeout.WithHandler(func(c *gin.Context) {
			time.Sleep(199 * time.Microsecond)
			c.JSON(http.StatusOK, gin.H{
				"code": 200,
				"data": "",
			})
		}),
		timeout.WithResponse(func(c *gin.Context) {
			c.JSON(http.StatusRequestTimeout, gin.H{
				"code":    408,
				"message": "test",
			})
		})))

Error:

[marko1777]

if you use apach benchmark you can easily reproduce this issue
ab -n 3000 -c 500 localhost:8080/

func timeoutMiddleware() gin.HandlerFunc {
   return timeout.New(
   	timeout.WithTimeout(2*time.Second),
   	timeout.WithHandler(func(c *gin.Context) {
   		c.Next()
   	}),
   	timeout.WithResponse(testResponse),
   )
}

func main() {
   router := gin.Default()
   router.Use(timeoutMiddleware())
}

[x-lambda]

// Header will get response headers
func (w *Writer) Header() http.Header {
	for i := 0; i < 100000; i++ {
		w.headers["a"] = []string{"b"}
	}

	return w.headers
}

Actually, I use for{} write map When call Header(), it's 100% panic.

This proves that 2 gotoutine are operating with header in parallel