Does Go Cache DNS Lookups?

Does Go Cache DNS Lookups?

Question:

Are DNS queries cached in Go (golang) to optimize request performance? If not, does the underlying operating system or network infrastructure on Debian/Ubuntu/Linux, Windows, or Darwin/OSX implement caching mechanisms that Go applications can leverage?

Answer:

The Go standard library's DNS resolver does not have built-in caching capabilities. However, external solutions exist to address this issue.

One recommended solution is the dnscache package, which provides efficient caching of DNS lookups. You can integrate this package into your Go applications to enhance DNS performance.

For example, the following code snippet demonstrates how to integrate dnscache with the standard HTTP client to enable caching for all HTTP requests:

<code class="go">import (
    "net/http"

    "github.com/miekg/dns"
)

func main() {
    // Set the custom DNS dialer that uses the dnscache package.
    http.DefaultClient.Transport = &http.Transport{
        MaxIdleConnsPerHost: 64,
        Dial: func(network string, address string) (net.Conn, error) {
            separator := strings.LastIndex(address, ":")
            ip, _ := dns.FetchString(address[:separator])
            return net.Dial("tcp", ip+address[separator:])
        },
    }

    // Make HTTP requests as usual, benefiting from DNS caching.
}</code>

By customizing the dialer function in the HTTP transport, Go applications can leverage the caching capabilities of the dnscache package, reducing unnecessary DNS lookups and improving overall request performance.

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