Why Does My Web Server Seem to Be Called an Even Number of Times?

Why is a Web Server Called Even Number Times?

In web programming, a server responds to incoming requests. However, our simple web server is called on seemingly random even-numbered times.

Under the Hood Requests

Upon refreshing the page, you might observe the following:

You've called me 1 times
You've called me 3 times
You've called me 5 times
....

This happens because the browser makes additional requests in the background. One common request is for favicon.ico, an icon usually displayed next to the title of a web page.

Web Server Response

Our web server does not handle the favicon.ico request, leading it to be continuously requested by the browser. This request increments our counter, resulting in even-numbered calls.

Synchronization and Control

Go concurrently handles requests using goroutines. This can lead to a race condition in our code, where the calls variable is incremented by multiple goroutines simultaneously. To prevent this, we synchronize access to the variable using atomic operations.

Alternatively, we can prevent the counter from being incremented for every request by checking the request path and ignoring requests not destined for our root endpoint.

Code Fix

To ensure accurate call counting, we can either synchronize access to the calls variable or selectively ignore certain requests, such as favicon.ico:

// Use atomic operations
func HelloWorld(w http.ResponseWriter, r *http.Request) {
    count := atomic.AddInt64(&calls, 1)
    fmt.Fprintf(w, "You've called me %d times", count)
}

// Ignore specific requests
func HelloWorld(w http.ResponseWriter, r *http.Request) {
    if r.URL.Path != "/" || r.URL.Path == "/favicon.ico" {
        return
    }
    count := atomic.AddInt64(&calls, 1)
    fmt.Fprintf(w, "You've called me %d times", count)
}

By implementing these modifications, our web server will count calls accurately, regardless of additional browser requests.

The above is the detailed content of Why Does My Web Server Seem to Be Called an Even Number of Times?. For more information, please follow other related articles on the PHP Chinese website!